ICSE Class 10 Physics Important Questions Chapter wise

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    ICSE Class 10 Physics Important Questions Chapter wise for Students

    The speed of sound in air is 300 m/s. The distance between two successive nodes of a stationary wave of frequency 1000 Hz is :

    (A) 10 cm

    (B) 15 cm

    (C) 20 cm

    (D) 30 cm

    Explanation:

    This question asks us to determine the separation between two consecutive nodes in a stationary sound wave when the velocity of sound and the frequency of the wave are known.

    Stationary waves are formed when two waves of equal frequency and amplitude travel in opposite directions and interfere with each other. This interference creates fixed points called nodes where the displacement of particles is always zero. Between these nodes are antinodes where the vibration amplitude is maximum. The spatial arrangement of nodes and antinodes depends on the wavelength of the wave.

    To solve this conceptually, we first recall the basic wave relation connecting wave speed (v), frequency (f), and wavelength (λ): v = fλ. Using the given wave speed and frequency, the wavelength of the sound wave can be determined. Once the wavelength is known, the pattern of stationary waves becomes important. In such waves, the distance between two consecutive nodes equals half of the wavelength (λ/2). This occurs because nodes correspond to points of destructive interference that repeat at regular intervals along the medium. Therefore, after determining the wavelength from the wave equation, the node-to-node separation can be expressed as a fraction of that wavelength.

    A helpful analogy is a vibrating guitar string fixed at both ends. Certain points on the string remain motionless while the rest of the string vibrates, forming evenly spaced stationary points.

    In summary, the problem requires determining the wavelength using the wave equation and then applying the stationary-wave rule that successive nodes occur at half-wavelength intervals.

    Option b – 15 cm

    A stationary wave of frequency 300 Hz is formed in a medium in which the velocity of sound is 1200 m/s. The distance between a node and the neighboring antinode is ( ICSE Class 10 Physics Important Questions )

    (A) 1 m

    (B) 2 m

    (C) 3 m

    (D) 4 m

    Explanation:

    This question asks for the spatial separation between a node and its nearest antinode in a stationary wave formed in a medium with a known sound velocity and wave frequency.

    In stationary waves, nodes are positions where the medium does not move, while antinodes are positions where the Oscillation amplitude is maximum. These points occur because two waves traveling in opposite directions interfere with each other. The positions of nodes and antinodes are determined by the wavelength of the wave.

    To approach the problem, begin with the fundamental wave relation v = fλ, which links the velocity of the wave to its frequency and wavelength. From the given values, the wavelength of the wave can be determined. Once the wavelength is known, the geometry of stationary waves provides the next step. Nodes occur at intervals of λ/2, but an antinode lies exactly midway between two nodes. Therefore, the distance between a node and its closest antinode corresponds to one-quarter of the wavelength (λ/4). This consistent spatial pattern arises from the repeating sequence of constructive and destructive interference along the medium.

    A useful comparison is the pattern formed in a vibrating rope tied at both ends. Some points remain still, while other points show maximum motion, forming a repeating pattern of stationary and vibrating points.

    In summary, the required distance can be determined by first calculating the wavelength and then applying the stationary-wave property that the node-to-antinode separation equals one-quarter of the wavelength.

    Option a – 1 m

    In stationary waves, all the particles of the medium are :

    (A) At rest together two times in each time period

    (B) At rest together once in each time period

    (C) Never at rest together

    (D) Not at rest under any condition

    Explanation:

    This question asks about the collective motion of particles in a medium when a stationary wave is formed, specifically whether all particles can simultaneously come to rest at certain moments.

    Stationary waves arise when two waves of equal amplitude and frequency move in opposite directions and interfere with each other. This interference produces nodes, where displacement is always zero, and antinodes, where displacement reaches maximum values. The particles in the medium oscillate about their equilibrium positions but do not Transport energy along the medium.

    To understand the behavior of particles, consider the motion of each particle in the stationary wave. Every particle between nodes vibrates with simple harmonic motion but with different amplitudes depending on its position. However, at certain instants during the Oscillation cycle, all particles simultaneously pass through their equilibrium positions. At these moments, their instantaneous displacement becomes zero. When the displacement becomes zero, the particles temporarily come to rest before reversing direction. Because the Oscillation pattern repeats periodically, such instants occur regularly within each time period of vibration. Thus, the simultaneous state of rest occurs at specific moments during the Oscillation cycle.

    An easy analogy is a group of children on swings moving back and forth. Even though each swing has different height of motion, there are moments when all swings pass through the center position together.

    In summary, stationary waves allow all particles of the medium to reach the equilibrium position simultaneously at certain instants during each Oscillation cycle.

    Option a – At rest together two times in each time period

    In stationary waves, antinodes are the points where there are: ( ICSE Class 10 Physics Important Questions )

    (A) Minimum displacement and minimum pressure change

    (B) Minimum displacement and maximum pressure change

    (C) Maximum displacement and maximum pressure change

    (D) Maximum displacement and minimum pressure change

    Explanation:

    This question asks about the physical characteristics of antinodes in stationary waves, particularly how displacement and pressure variations behave at those locations.

    Stationary waves consist of alternating nodes and antinodes formed through interference of two waves traveling in opposite directions. At nodes, the displacement of the medium is always zero due to complete destructive interference. At antinodes, constructive interference occurs, resulting in the largest possible oscillations of particles in the medium.

    To reason through the behavior at antinodes, consider how particle motion and pressure variations are related in sound waves. When particles vibrate with large amplitudes, they move farther from their equilibrium positions. This produces regions of compression and rarefaction that influence local pressure. However, at the point where particle displacement reaches its maximum, the instantaneous pressure variation tends to be minimal because particles momentarily stop before reversing direction. This relationship between displacement and pressure variation leads to a characteristic pattern where maximum displacement corresponds to a minimum pressure change.

    A simple analogy is a stretched spring oscillating back and forth. The points where the coils stretch the most represent the positions of maximum displacement in the vibration pattern.

    In summary, antinodes are the locations in stationary waves where the Oscillation amplitude of particles is greatest, while pressure variations behave differently compared with nodes.

    Option d – Maximum displacement and minimum pressure change

    Which of the following changes at an antinode in a stationary wave?

    (A) Density only

    (B) Pressure only

    (C) Both pressure and density

    (D) Neither pressure nor density

    Explanation:

    This question asks which physical quantities change at an antinode in a stationary wave, focusing on how properties such as pressure and density behave at these points.

    In sound waves traveling through a medium, particles oscillate back and forth about their equilibrium positions. This motion creates variations in pressure and density, producing compressions and rarefactions. In stationary waves, interference between two waves traveling in opposite directions creates fixed nodes and antinodes with distinct characteristics.

    To analyze the situation at an antinode, consider the motion of particles at this location. Antinodes represent points where the displacement of particles is maximum because constructive interference occurs there. As particles oscillate with large amplitude, the surrounding medium undergoes changes in both pressure and density due to alternating compression and expansion. These variations arise because the movement of particles alters the spacing between molecules in the medium. As a result, pressure and density fluctuations occur together as part of the wave motion.

    A helpful analogy is compressing and releasing a sponge repeatedly. As the sponge expands and contracts, both its density and internal pressure distribution change simultaneously.

    In summary, the physical conditions at antinodes involve significant oscillatory motion of particles, leading to changes in the properties of the medium associated with sound-wave propagation.

    Option d – Neither pressure nor density

    Which of the following properties makes difference between progressive and stationary waves? ( ICSE Class 10 Physics Important Questions )

    (A) Amplitude

    (B) Frequency

    (C) Propagation of energy

    (D) Phase of wave

    Explanation:

    This question asks which physical characteristic distinguishes progressive waves from stationary waves in wave motion.

    Progressive waves travel through a medium by transferring energy from one point to another. In contrast, stationary waves are formed by the superposition of two waves moving in opposite directions with equal frequency and amplitude. Instead of moving through the medium, stationary waves produce a pattern of nodes and antinodes where the wave pattern appears fixed.

    To determine the distinguishing property, consider how energy behaves in these two wave types. In progressive waves, energy is continuously transported through the medium as the wave propagates forward. Particles of the medium oscillate about their equilibrium positions, but the disturbance travels along the medium carrying energy with it. In stationary waves, however, the wave pattern remains fixed in space. Although particles still vibrate, the energy does not travel from one region to another. Instead, energy is confined within the standing-wave pattern between nodes and antinodes.

    An analogy is the difference between ocean waves traveling toward the shore and ripples trapped between two barriers that only oscillate in place.

    In summary, the key property distinguishing progressive waves from stationary waves relates to whether energy is transported through the medium or remains localized in a fixed vibration pattern.

    Option c – Propagation of energy

    In stationary waves, all particles between two nodes pass through the mean position :

    (A) At different times with different velocities

    (B) At different times with the same velocity

    (C) At the same time with equal velocity

    (D) At the same time with different velocities

    Explanation:

    This question asks about the motion of particles located between two nodes in a stationary wave and whether they pass through their equilibrium position at the same or different times.

    In stationary waves, the medium forms a pattern of nodes and antinodes due to interference between two opposite-traveling waves. Particles between nodes oscillate with simple harmonic motion. Although their amplitudes vary depending on their distance from the node, their motion follows the same Oscillation frequency.

    To understand the timing of their motion, consider the mathematical form of stationary waves. All particles between two adjacent nodes vibrate with the same frequency and phase relationship. Because the phase is the same across this region, the particles reach their equilibrium positions simultaneously during each Oscillation cycle. However, the amplitude of vibration varies from zero at the nodes to maximum at the antinode. Despite this amplitude difference, the velocity with which particles pass through the mean position depends on their amplitude, meaning it may vary between particles.

    A simple analogy is a group of pendulums of different lengths attached to a moving platform. Even though their amplitudes differ, they can cross their central positions simultaneously due to synchronized motion.

    In summary, particles between two nodes in a stationary wave oscillate together with the same phase, allowing them to pass through their equilibrium position at the same instant.

    Option d – At the same time with different velocities

    Stationary waves :

    (A) Transport energy

    (B) Does not Transport energy

    (C) Have crests and troughs

    (D) Have compressions and rarefactions

    Explanation:

    This question concerns a fundamental property of stationary waves, particularly how they behave with respect to energy transfer in a medium.

    Stationary waves, also called standing waves, are formed when two waves of the same frequency and amplitude travel in opposite directions and interfere with each other. This interference creates fixed points known as nodes and antinodes. At nodes, the displacement of particles remains zero, while at antinodes the amplitude of vibration becomes maximum.

    To analyze their behavior, consider how energy typically moves in wave motion. In progressive waves, the disturbance travels through the medium and carries energy from one location to another. However, the pattern in stationary waves remains fixed in space. Although particles continue to oscillate, the energy associated with the wave does not propagate along the medium. Instead, it oscillates locally between kinetic and potential forms around the nodes and antinodes. This characteristic distinguishes stationary waves from traveling waves.

    An example can be seen in a stretched string fixed at both ends when it vibrates at specific frequencies. The pattern of nodes and antinodes remains stationary even though the string segments are moving.

    In summary, stationary waves are characterized by a fixed pattern of vibration where energy remains confined within the system rather than traveling through the medium.

    Option b – Does not Transport energy

    In stationary waves : ( ICSE Class 10 Physics Important Questions )

    (A) Energy is uniformly distributed

    (B) Energy is minimum at nodes and maximum at antinodes

    (C) Energy is maximum at nodes and minimum at antinodes

    (D) Alternating maximum and minimum energy producing at nodes and antinodes

    Explanation:

    This question examines how energy is distributed in different regions of a stationary wave, particularly at nodes and antinodes.

    In wave motion, energy is associated with both kinetic energy of moving particles and potential energy due to elastic deformation of the medium. In progressive waves, this energy travels through the medium along with the wave disturbance. However, stationary waves behave differently because their pattern does not propagate.

    To analyze energy distribution in stationary waves, consider the motion of particles at nodes and antinodes. At nodes, particles remain at rest with zero displacement and zero velocity. Since both displacement and velocity are zero at these points, the energy associated with particle motion becomes minimal. At antinodes, however, particles vibrate with maximum amplitude and achieve the highest velocities during Oscillation. Because kinetic energy is proportional to the square of velocity (v2), regions near antinodes possess significantly higher energy compared to nodes. This results in a pattern where energy is concentrated around antinodes and minimal near nodes.

    A helpful comparison is a vibrating rope where the middle sections move vigorously while certain fixed points remain almost motionless.

    In summary, stationary waves exhibit a non-uniform energy distribution where vibrating regions carry greater energy while nodes remain nearly energy-free.

    Option b – Energy is minimum at nodes and maximum at antinodes

    Stationary waves cannot be produced in the:

    (A) Thin wire

    (B) Thick wire

    (C) Short wire

    (D) Infinitely long wire

    Explanation:

    This question asks about the physical conditions required for the formation of stationary waves and in which type of system such waves cannot be produced.

    Stationary waves are formed when two waves of equal frequency and amplitude travel in opposite directions and interfere with each other. This situation commonly occurs when waves reflect from boundaries such as fixed ends of strings, closed pipes, or rigid surfaces. The reflected wave combines with the incident wave to create nodes and antinodes.

    To determine where stationary waves cannot form, consider the importance of boundaries in wave reflection. For standing waves to develop, the wave must reflect back through the same medium and overlap with the incoming wave. This requires a confined system where reflections occur repeatedly. If the medium extends infinitely without any reflecting boundary, the wave continues to propagate forward without returning to interfere with itself. Without this interference, the characteristic pattern of nodes and antinodes cannot form.

    An analogy is shouting in a canyon versus an open field. In a canyon, echoes return and interfere with the original sound, while in an open field the sound simply travels away.

    In summary, stationary waves require reflecting boundaries, and therefore they cannot be formed in a system where waves cannot return to interfere with the original wave.

    Option d – Infinitely long wire

    The maximum possibility of turbulent flow is in a Fluid of ( ICSE Class 10 Physics Important Questions )

    (A) low density and low viscosity

    (B) high density and high viscosity

    (C) low density and high viscosity

    (D) high density and low viscosity

    Explanation:

    The question asks which type of Fluid conditions increase the likelihood of turbulent flow rather than smooth laminar motion. Understanding how Fluid properties influence flow behavior helps determine when turbulence occurs.

    Fluid flow inside pipes or channels can occur in two main regimes: laminar flow and turbulent flow. Laminar flow is orderly, with Fluid layers moving smoothly without mixing. Turbulent flow, on the other hand, involves chaotic motion, eddies, and mixing of Fluid layers. The transition between these two regimes is primarily determined by the Reynolds number, a dimensionless quantity depending on density, velocity, viscosity, and pipe diameter.

    To reason through the question, recall that the Reynolds number is given by the relation Re = ρvD/η, where ρ is density, v is velocity, D is diameter of the pipe, and η is viscosity of the Fluid. A larger Reynolds number favors turbulence. This means turbulence becomes more likely when velocity or density is large or when viscosity is small. Viscosity represents internal resistance to flow; fluids with high viscosity resist mixing and maintain smooth layers, which supports laminar flow. Conversely, when viscosity is very low, Fluid layers slide past each other easily and disturbances grow rapidly, leading to chaotic motion.

    A helpful analogy is traffic flow on a highway. Thick traffic moving slowly behaves in an orderly way like laminar flow, while fast-moving Light traffic with disturbances quickly becomes irregular, resembling turbulence.

    In summary, turbulence is most likely in fluids whose physical properties increase the Reynolds number, particularly when internal resistance to motion is very small.

    Option d – high density and low viscosity

    Which of the following is not characteristic of turbulent flow?

    (A) Velocity more than the critical velocity

    (B) Velocity less than the critical velocity

    (C) Irregular flow

    (D) Molecules crossing from one layer to another

    Explanation:

    This question asks us to recognize a property that does not belong to turbulent flow. To answer this, it is important to understand the fundamental characteristics that define turbulent motion in fluids.

    Turbulent flow occurs when the orderly motion of Fluid layers breaks down and becomes chaotic. In this regime, Fluid particles move irregularly, forming vortices and eddies that continuously mix neighboring layers. This mixing increases momentum transfer and energy dissipation. Turbulent flow usually occurs when the Reynolds number becomes large, typically due to high velocity or low viscosity.

    To analyze the options conceptually, consider the defining features of turbulent motion. In turbulence, the velocity of fluid particles fluctuates rapidly both in magnitude and direction. The flow pattern is irregular and unpredictable compared with laminar flow. Strong mixing between layers occurs, which enhances the Transport of energy and momentum. Because of this mixing, energy losses due to friction become significant. Therefore, any statement that describes smooth, parallel layers moving without mixing would contradict the nature of turbulence. Such characteristics belong to laminar flow instead.

    An easy way to visualize this difference is to compare a calm river with a fast-moving waterfall. Calm water moves smoothly in layers, whereas the waterfall produces chaotic swirling patterns.

    In summary, identifying the correct option requires recognizing which description contradicts the chaotic, irregular, and strongly mixed nature of turbulent fluid motion.

    Option b – Velocity less than the critical velocity

    When the velocity of a liquid is greater than its critical velocity then the flow of the liquid will be : ( ICSE Class 10 Physics Important Questions )

    (A) streamline

    (B) turbulent

    (C) sometimes streamlined and sometimes turbulent

    (D) none of the above

    Explanation:

    This question asks what type of flow develops when the speed of a liquid exceeds a particular threshold known as the critical velocity.

    Critical velocity is the maximum velocity at which fluid flow remains laminar or streamlined. Below this value, fluid layers move smoothly in parallel paths without mixing. The concept of critical velocity is closely linked to the Reynolds number, which determines whether the flow remains orderly or becomes chaotic.

    To reason through this situation, consider what happens when the velocity of a liquid gradually increases inside a pipe. At low speeds, the flow remains stable and layered. However, as the velocity approaches the critical value, disturbances begin to appear in the fluid. If the velocity exceeds this limit, these disturbances grow rapidly, causing the layers of fluid to break down and mix. The motion becomes irregular with eddies and swirling patterns. This transition marks the change from laminar flow to another flow regime characterized by random motion of fluid particles.

    A simple analogy is the behavior of smoke rising from a candle. Close to the flame the smoke rises smoothly in a thin column, but after some distance it begins to twist and swirl as the flow becomes unstable.

    In summary, when the velocity of a liquid becomes greater than its critical velocity, the orderly structure of laminar flow breaks down and the fluid enters a more chaotic flow regime.

    Option b – turbulent

    In turbulent flow, the velocity of the liquid molecules in contact with the walls of the tube :

    (A) is zero

    (B) is maximum

    (C) may have any value

    (D) is equal to the critical velocity

    Explanation:

    The question focuses on the velocity of fluid molecules that are directly touching the walls of a tube during turbulent flow. Understanding boundary behavior is essential in fluid dynamics.

    In any real fluid flowing through a pipe, the molecules in immediate contact with the pipe wall adhere to the surface due to Molecular attraction. This phenomenon is known as the no-slip condition. According to this principle, the velocity of the fluid layer touching the boundary becomes equal to the velocity of the boundary itself.

    To analyze the situation further, note that turbulent flow involves irregular motion and mixing of fluid layers in the interior region of the pipe. Despite this chaotic motion, the boundary condition at the wall still holds true. The fluid layer in direct contact with the wall cannot move freely because of frictional interaction between the molecules and the Solid surface. As a result, the velocity gradually increases from the wall toward the center of the pipe, creating a velocity gradient across the radius. Even though turbulence changes the velocity profile in the pipe, the immediate boundary layer still follows the same fundamental rule.

    An analogy can be seen when dragging a book across a table. The bottom surface touching the table experiences friction and cannot move independently, while the upper layers move more freely.

    In summary, although turbulent flow contains complex motion within the fluid, the molecules directly touching the pipe wall follow the boundary condition that restricts their motion relative to the surface.

    Option c – may have any value

    For the flow of a fluid to be turbulent : ( ICSE Class 10 Physics Important Questions )

    (A) fluid should have high density

    (B) critical velocity should be large

    (C) Reynold’s number should be less than 2000

    (D) all the above

    Explanation:

    This question asks what physical condition must be satisfied for a flowing fluid to exhibit turbulent behavior instead of laminar motion.

    Fluid flow patterns depend on the balance between inertial forces and viscous forces within the liquid. When viscous forces dominate, fluid layers remain stable and move smoothly in parallel paths. When inertial forces become much larger than viscous resistance, disturbances grow rapidly and produce chaotic motion.

    To analyze the requirement for turbulence, consider the role of the Reynolds number. This dimensionless quantity compares inertial forces to viscous forces in a flowing fluid. When the Reynolds number is small, viscous forces damp disturbances and maintain laminar flow. As velocity, density, or pipe diameter increases, the Reynolds number increases as well. Beyond a certain threshold value, viscous forces are no longer able to suppress disturbances. The fluid then develops random fluctuations in velocity, forming vortices and eddies throughout the flow. This condition marks the onset of turbulence.

    A helpful analogy is a crowd walking through a narrow corridor. If everyone moves slowly and orderly, the flow remains smooth. When people move quickly and push each other, the motion becomes chaotic.

    In summary, turbulent flow occurs when the dynamic conditions of the fluid cause inertial forces to dominate over viscous forces, allowing disturbances in the flow to grow uncontrollably.

    Option a – fluid should have high density

    In the case of streamlining the flow of a non-viscous and incompressible liquid through a tube of nonuniform cross-section, what will be the ratio of masses of liquid entering and coming out of the tube? The ratio of cross sections of the tube at two places is 5 : 1

    (A) 1 : 1

    (B) 2 : 5

    (C) 1:25

    (D) 5 : 2

    Explanation:

    The question investigates how the Mass of a fluid entering and leaving a tube changes when the cross-sectional area of the tube varies, assuming streamlined flow of an incompressible liquid.

    In fluid dynamics, the principle of continuity governs the flow of incompressible fluids through pipes. According to this principle, the Mass flow rate remains constant along the tube. This means the amount of Mass passing through any cross-section of the tube per unit time must remain the same, regardless of changes in cross-sectional area.

    To analyze this situation, imagine liquid flowing through a tube that becomes narrower or wider at different points. When the cross-sectional area decreases, the fluid must move faster to maintain the same Mass flow rate. Conversely, when the area increases, the velocity decreases. This adjustment ensures that the product of cross-sectional area, velocity, and density remains constant. Because the liquid is incompressible, its density remains unchanged. Therefore, even if the areas at two points differ significantly, the total Mass of fluid entering the tube per unit time must equal the Mass leaving it.

    An everyday analogy is traffic entering and leaving a tunnel. Even if the road narrows temporarily, the number of cars entering and exiting per unit time must remain balanced.

    In summary, under steady streamlined flow of an incompressible fluid, the conservation of Mass ensures that the Mass entering and leaving the tube remains constant.

    Option a – 1 : 1

    Which of the following is not the property of laminar flow? ( ICSE Class 10 Physics Important Questions )

    (A) Flow may be along a curved path

    (B) Velocity of flow is independent of time

    (C) Velocity of flow may be different at different points

    (D) Liquid molecules may cross from one layer into the other

    Explanation:

    This question asks us to identify a characteristic that does not belong to laminar flow. To answer this, it is essential to recall the defining features of laminar motion in fluids.

    Laminar flow occurs when fluid particles move in smooth, parallel layers with minimal mixing between them. Each layer slides past neighboring layers without disrupting the overall structure of the flow. This type of flow typically occurs when the velocity of the fluid is relatively low and the Reynolds number remains below a critical value.

    To reason through the question, consider the properties commonly associated with laminar flow. The motion of particles is highly ordered and predictable, with no sudden fluctuations in velocity. Energy loss due to internal friction is relatively small compared with turbulent flow. The velocity at any point in the fluid remains steady over time. Because there is little mixing between layers, the flow pattern remains stable and well-defined. Therefore, any statement describing irregular motion, swirling eddies, or strong mixing between layers would contradict the nature of laminar flow and would instead represent characteristics of turbulent motion.

    An easy comparison is the smooth flow of honey poured slowly from a jar, which forms steady layers without chaotic motion.

    In summary, identifying the correct option requires recognizing the feature that contradicts the orderly, smooth, and layered structure of laminar fluid flow.

    Option d – Liquid molecules may cross from one layer into the other

    In streamline flow, which of the following is correct?

    (A) The speed of flow at all points in space is necessarily the same

    (B) the speed of every particle at one point is the same but it is different at different points in place

    (C) the velocity of every particle at a particular point is the same

    (D) the velocity of different particles at the same point in space is different

    Explanation:

    The question focuses on identifying the correct statement about streamline flow, a common form of laminar motion observed in fluid dynamics.

    Streamline flow refers to a condition where fluid particles move along well-defined paths called streamlines. In this regime, the velocity of the fluid at any given point remains constant with time, and the motion of the fluid occurs in smooth parallel layers. This type of flow generally occurs when the velocity of the fluid is relatively small and the Reynolds number remains below the critical value.

    To determine the correct statement, it is helpful to analyze the basic features of streamline motion. In this flow pattern, each particle follows a fixed path without crossing neighboring streamlines. Because the motion is orderly, there is minimal mixing between layers. The velocity distribution across the pipe remains stable and predictable. Disturbances in the flow quickly die out due to viscous forces. Any statement that involves irregular fluctuations, vortices, or chaotic motion would contradict the idea of streamline flow and instead describe turbulence.

    A simple analogy is cars moving smoothly in separate lanes on a highway, where each car follows a predictable path without sudden mixing between lanes.

    In summary, the correct option must describe the stable, orderly, and predictable motion of fluid particles along fixed paths characteristic of streamline flow.

    Option c – the velocity of every particle at a particular point is the same

    When a fluid is in streamlined flow, then the reason for the viscous force acting between its two layers is : ( ICSE Class 10 Physics Important Questions )

    (A) Transport of energy from one layer to another

    (B) Transport of linear momentum from one layer to another

    (C) the same velocity of molecules

    (D) the variable density along the length of the tube

    Explanation:

    This question examines the origin of viscous force between adjacent layers of a fluid when the fluid is flowing in a streamlined or laminar manner.

    Viscosity is a property of fluids that represents their internal resistance to flow. When different layers of a fluid move at different velocities, frictional forces arise between them. These forces oppose the relative motion of the layers and attempt to equalize their velocities. This internal friction is known as viscous force.

    To reason through this situation, consider a fluid flowing through a pipe. The layer of fluid touching the pipe wall moves more slowly due to friction with the surface, while layers farther from the wall move faster. Because these layers have different velocities, there is a relative motion between them. Molecular interactions within the fluid cause momentum to be transferred from faster layers to slower layers. This transfer of momentum results in a resistive force that opposes the motion. The greater the difference in velocity between layers, the stronger the viscous force acting between them.

    An everyday example can be observed when sliding a deck of cards across a table. Each card moves slightly relative to the others, and friction between them resists the motion.

    In summary, viscous force in streamlined flow arises due to the relative motion and velocity differences between adjacent layers of the fluid.

    Option b – Transport of linear momentum from one layer to another

    In a laminar flow; the velocity of flow at any point in the liquid :

    (A) does not vary with time

    (B) may vary in magnitude but not in the direction

    (C) may vary in direction but not in magnitude

    (D) may vary both in magnitude and direction

    Explanation:

    The question asks about how the velocity of a fluid behaves at a specific point when the fluid is moving in laminar flow.

    Laminar flow is characterized by smooth and orderly motion of fluid layers. Each layer moves parallel to the others without mixing. In such a flow regime, the motion of the fluid is highly predictable, and physical quantities such as velocity and pressure change gradually rather than fluctuating randomly.

    To analyze the behavior of velocity, imagine observing a particular point inside a pipe carrying a slowly moving liquid. In laminar flow, the pattern of motion remains stable over time. As a result, the velocity of the fluid at that point does not change randomly. Instead, it remains constant with time, provided the flow conditions such as pressure difference and pipe geometry remain unchanged. However, the velocity may vary from one location to another within the pipe. Typically, the velocity is lowest near the walls due to friction and highest at the center of the pipe. This creates a smooth velocity profile across the cross-section.

    A useful analogy is water flowing slowly in a straight canal where the motion remains steady and predictable.

    In summary, in laminar flow the velocity at any given point remains steady with time even though the magnitude of velocity may differ from one location in the fluid to another.

    Option a – does not vary with time

    In streamlined flow, the velocity of the liquid in contact with the containing vessel is : ( ICSE Class 10 Physics Important Questions )

    (A) zero

    (B) large

    (C) minimum but not zero

    (D) infinite

    Explanation:

    This question examines the behavior of fluid velocity at the boundary where the liquid directly touches the surface of a container or pipe during streamlined flow.

    In fluid mechanics, the motion of liquids near Solid boundaries follows a principle known as the no-slip condition. According to this concept, the layer of fluid in immediate contact with a Solid surface adheres to that surface due to intermolecular forces between the liquid and the Solid. Because of this interaction, the fluid cannot move freely at the boundary.

    To understand the reasoning, imagine liquid flowing through a pipe. The pipe wall exerts friction on the fluid molecules that touch it. These molecules experience strong attractive forces with the surface and cannot slide freely relative to it. As a result, their velocity becomes the same as the velocity of the wall. If the pipe itself is stationary, the fluid layer touching it also becomes stationary. Moving away from the wall toward the center of the pipe, the velocity gradually increases until it reaches its maximum value at the center. This gradual change creates a velocity gradient across the fluid layers.

    An everyday example can be observed when honey flows along the inner surface of a container. The honey touching the wall moves extremely slowly compared with the layers near the middle.

    In summary, the fluid layer directly touching the container wall follows the boundary condition that restricts its motion relative to the Solid surface.

    Option a – zero

    The flow of liquid in laminar or streamlined is determined by the:

    (A) the rate of flow of liquid

    (B) the density of the liquid

    (C) the radius of the tube

    (D) the coefficient of viscosity of the liquid

    Explanation:

    The question asks which physical quantity determines whether the flow of a liquid will remain laminar or streamlined rather than becoming turbulent.

    Fluid flow regimes depend on the balance between two competing influences: inertial forces that tend to disturb the motion and viscous forces that resist such disturbances. When viscous forces dominate, the fluid layers remain stable and move smoothly in parallel paths, producing laminar flow.

    To analyze this situation, physicists use a dimensionless quantity known as the Reynolds number. This parameter compares the magnitude of inertial forces to viscous forces in a flowing fluid. It depends on several factors including the density of the fluid, its velocity, the characteristic dimension of the pipe or channel, and the fluid’s viscosity. When the Reynolds number is small, viscous forces effectively damp any disturbances, and the fluid flows in a smooth and orderly manner. As the Reynolds number increases beyond a critical value, inertial forces become dominant and the flow begins to transition toward turbulence.

    A simple analogy is the flow of people through a narrow hallway. If individuals move slowly and steadily, the movement remains orderly. If they move rapidly, collisions and irregular motion begin to appear.

    In summary, determining whether a fluid flows in a laminar or turbulent manner requires evaluating the physical parameter that compares inertial effects with viscous resistance.

    Option a – the rate of flow of liquid

    Streamline flow is more likely for liquids with ( ICSE Class 10 Physics Important Questions )

    (A) high density and low viscosity

    (B) low density and high viscosity

    (C) high density and high viscosity

    (D) low density and low viscosity

    Explanation:

    The question asks which type of fluid properties favor the occurrence of streamline or laminar flow rather than turbulent motion.

    Streamline flow occurs when fluid particles move in smooth, parallel layers without mixing. This orderly motion typically occurs when the Reynolds number remains below a certain critical value. The Reynolds number depends on the fluid’s density, velocity, characteristic length scale, and viscosity.

    To understand which conditions favor streamline flow, consider the role of viscosity. Viscosity represents the internal friction within a fluid. High viscosity means the fluid strongly resists relative motion between its layers. Because of this resistance, disturbances in the flow quickly die out before they can develop into chaotic motion. As a result, fluids with greater internal friction tend to maintain smooth and stable flow patterns even when moving through pipes or channels. Conversely, fluids with very low viscosity allow disturbances to grow more easily, making turbulence more likely.

    An everyday example is the difference between honey and water flowing through a tube. Honey moves slowly and smoothly due to strong internal resistance, while water can become turbulent much more easily.

    In summary, streamline flow is favored in liquids whose internal properties suppress disturbances and help maintain stable motion between neighboring fluid layers.

    Option b – low density and high viscosity

    A liquid column of vertical height 1.2 m exerts a pressure of 19992 Pa at the bottom. The density of the liquid is :

    (A) 1400 kg/m³

    (B) 1600 kg/m³

    (C) 1500 kg/m³

    (D) 1700 kg/m³

    Explanation:

    This question asks how to determine the density of a liquid when the pressure exerted by a vertical column of that liquid and its height are known.

    In fluid statics, the pressure at a certain depth within a liquid arises due to the weight of the liquid column above that point. The pressure depends on three main factors: the density of the liquid, the acceleration due to gravity, and the vertical height of the liquid column.

    To approach this problem, recall the hydrostatic pressure relation
    𝑃
    =
    𝜌
    𝑔

    P=ρgh, where
    𝑃
    P is pressure,
    𝜌
    ρ is the density of the liquid,
    𝑔
    g is the acceleration due to gravity, and

    h is the height of the liquid column. The equation shows that pressure increases linearly with both density and depth. Since the pressure and height are given in the problem, and the value of gravitational acceleration is known, the equation can be rearranged to determine the density. By substituting the known quantities into the formula and isolating the density term, the required value can be calculated.

    An intuitive example is stacking books on a table. The heavier the books and the taller the stack, the greater the force pressing down on the table.

    In summary, the density of the liquid can be determined by applying the hydrostatic pressure relation that connects pressure, density, gravitational acceleration, and the vertical height of the liquid column.

    Option d – 1700 kg/m³

    At what depth in the water the pressure will double the atmospheric pressure? ( ICSE Class 10 Physics Important Questions )

    (A) 10.34 m

    (B) 20.34 m

    (C) 15.34 m

    (D) 25.34 m

    Explanation:

    This question investigates the depth in water at which the total pressure becomes twice the atmospheric pressure experienced at the surface.

    In liquids at rest, pressure increases with depth because each layer of fluid supports the weight of the fluid above it. The total pressure at any depth is the sum of atmospheric pressure acting on the surface and the hydrostatic pressure produced by the water column.

    To analyze the situation, consider that hydrostatic pressure in a liquid is given by the relation
    𝑃
    =
    𝜌
    𝑔

    P=ρgh. At the surface of the water, the pressure equals atmospheric pressure alone. As we go deeper, the additional pressure from the water column increases linearly with depth. The question asks for the depth at which this additional pressure equals atmospheric pressure so that the total pressure becomes twice the atmospheric value. By equating the hydrostatic pressure to atmospheric pressure and solving for the depth, the required value can be obtained.

    A useful analogy is standing under a pile of sand. The deeper you go beneath the pile, the greater the weight pressing down from above.

    In summary, determining the required depth involves finding the height of the water column that produces hydrostatic pressure equal to atmospheric pressure.

    Option a – 10.34 m

    An Atmosphere :

    (A) is a unit of pressure

    (B) is a unit of force

    (C) gives us an idea of the composition of air

    (D) is the height above which there is no Atmosphere

    Explanation:

    This question relates to the concept of an Atmosphere as a unit of pressure and its significance in measuring forces exerted by gases or liquids.

    Pressure is defined as force acting per unit area. In many practical situations, particularly in meteorology and fluid mechanics, pressure is often expressed using the unit called Atmosphere. This unit historically originates from the average pressure exerted by Earth’s Atmosphere at sea level.

    To understand the concept, consider that the air surrounding Earth has weight due to gravity. The column of air above any point on the Earth’s surface exerts a force on that surface. When this force is distributed over an area, it produces atmospheric pressure. Scientists defined one Atmosphere as the pressure exerted by a specific height of mercury in a barometer under standard conditions. This standardization allows atmospheric pressure to be used as a convenient reference for comparing other pressure values in physics and engineering.

    A familiar example is the reading of a mercury barometer used in weather forecasting. The height of the mercury column reflects the atmospheric pressure at that location.

    In summary, the term Atmosphere represents a standard unit of pressure derived from the weight of Earth’s air column acting on a unit area at sea level.

    Option a – is a unit of pressure

    The pressure in a liquid at a given depth below the surface : ( ICSE Class 10 Physics Important Questions )

    (A) is always exerted downward

    (B) is the same in all directions

    (C) equals the total weight of liquid above that depth

    (D) depends upon the amount of liquid below the depth

    Explanation:

    This question asks about the factors that determine the pressure experienced at a particular depth beneath the surface of a liquid.

    In a fluid at rest, pressure arises because the layers of liquid above a point exert weight on the layers below. This pressure increases with depth because the amount of fluid above the point becomes larger. The concept is explained by hydrostatics, which studies fluids in equilibrium.

    To reason through the behavior of pressure, consider the hydrostatic pressure equation
    𝑃
    =
    𝜌
    𝑔

    P=ρgh. This formula indicates that pressure depends on the density of the liquid, gravitational acceleration, and the vertical depth below the surface. Interestingly, the pressure at a particular depth does not depend on the shape of the container or the total volume of liquid present. Only the height of the liquid column above the point matters. Therefore, points located at the same depth within the same liquid experience equal pressure regardless of the container’s geometry.

    An analogy is being underwater in a swimming pool. At a given depth, you feel the same pressure on your ears whether you are near the center or close to the side wall.

    In summary, the pressure at a given depth in a liquid depends primarily on the physical properties of the liquid and the vertical distance below the surface.

    Option b – is the same in all directions

    The pressure at the bottom of a liquid tank is not proportional to the :

    (A) acceleration due to gravity

    (B) the density of the liquid

    (C) height of the liquid

    (D) area of the liquid surface

    Explanation:

    The question explores which factor does not influence the pressure exerted by a liquid at the bottom of a container.

    Hydrostatic pressure depends on the vertical column of liquid above the point where pressure is measured. According to fluid statics, this pressure is determined by the relation
    𝑃
    =
    𝜌
    𝑔

    P=ρgh, where
    𝜌
    ρ is the density of the liquid,
    𝑔
    g is gravitational acceleration, and

    h is the depth of the liquid column.

    To understand what does not affect bottom pressure, consider the variables present in the equation. The pressure clearly depends on the density of the liquid and the vertical height of the liquid column. Gravity also plays an essential role because it determines the weight of the fluid. However, the equation does not contain terms related to the shape of the container or the total quantity of liquid present. This means that two containers with different shapes but filled to the same height with the same liquid will produce identical pressure at their bottoms.

    An everyday illustration is filling different-shaped bottles with water to the same height; the pressure at the bottom remains the same despite the differing volumes.

    In summary, hydrostatic pressure at the bottom of a liquid tank depends only on depth, density, and gravity, not on certain geometric or volumetric properties of the container.

    Option d – area of the liquid surface

    A disc is placed at the bottom of a water tank. The thrust on it due to water is E. If another disc of double the area is placed at the bottom of the same water tank, the thrust on it will be : ( ICSE Class 10 Physics Important Questions )

    (A) F

    (B) 3F

    (C) 2F

    (D) 4F

    Explanation:

    This question explores how the total force exerted by a liquid on a surface changes when the surface area changes while the pressure at that depth remains the same.

    In fluid mechanics, thrust is the force exerted by a fluid on a surface. It is calculated using the relation F = P × A, where F represents thrust, P is the pressure at that depth in the liquid, and A is the surface area on which the pressure acts.

    To analyze this situation, consider that both discs are placed at the bottom of the same tank. Since the depth of the liquid is identical at that point, the pressure acting on each disc remains unchanged. However, thrust depends on both pressure and area. If the area increases while the pressure remains constant, the force exerted by the liquid must increase proportionally. Therefore, changing the surface area alters the total force applied by the liquid, even though the pressure per unit area remains the same.

    A simple analogy is pressing your hand against water. If you increase the contact area, the total force experienced becomes larger even though the pressure of the water itself has not changed.

    In summary, thrust exerted by a liquid depends directly on both the pressure at that depth and the surface area over which the pressure acts.

    Option c – 2F

    The pressure at any point in a liquid depends upon :

    (A) the density of the liquid

    (B) the value of g

    (C) the depth of the point below the surface

    (D) all of the above

    Explanation:

    This question asks which physical factors determine the pressure experienced at a specific point within a liquid that is at rest.

    Pressure inside a liquid arises because each layer of the liquid supports the weight of the liquid above it. As the depth increases, more liquid lies above the point, resulting in a greater downward force and therefore higher pressure.

    The hydrostatic pressure in a liquid is described by the relation P = ρgh, where P is the pressure at depth, ρ is the density of the liquid, g is the acceleration due to gravity, and h is the vertical depth below the surface. This equation shows that pressure depends directly on the density of the liquid and the depth at which the pressure is measured. Gravity also influences the pressure because it determines the weight of the liquid column above the point. Importantly, the pressure at a particular depth does not depend on the shape or size of the container holding the liquid.

    For example, if you dive deeper into a swimming pool, the pressure on your body increases because the column of water above you becomes larger.

    In summary, pressure at any point in a liquid is determined by the physical properties of the liquid and the vertical depth below its surface.

    Option d – all of the above

    An open glass tube is immersed in mercury in such a way that a length of 8 cm extends above the mercury level. The open end of the tube is then closed and sealed and the tube is raised vertically up by an additional 46 cm. What will be the length of the air column above the mercury in the tube now? (Atmospheric pressure = 76 cm of Hg) ( ICSE Class 10 Physics Important Questions )

    (A) 38 cm

    (B) 6 cm

    (C) 16 cm

    (D) 22 cm

    Explanation:

    This question investigates how the length of an enclosed air column changes when a sealed tube containing trapped air is moved vertically in a liquid such as mercury.

    When air is trapped inside a tube and subjected to changes in pressure, its volume changes according to Boyle’s law. Boyle’s law states that for a fixed amount of gas at constant temperature, the product of pressure and volume remains constant. In mathematical form, this relationship is expressed as P1V1 = P2V2.

    To reason through the problem, first consider the initial condition of the air column inside the tube before it is raised. The trapped air experiences pressure from both atmospheric pressure and the mercury column surrounding it. When the tube is lifted upward, the pressure acting on the trapped air changes because the relative level of mercury inside and outside the tube shifts. As the external pressure decreases, the trapped air expands and occupies a greater length of the tube. By carefully applying Boyle’s law and considering the changes in pressure due to the mercury column, the new length of the air column can be determined.

    A helpful analogy is squeezing and releasing a balloon. When external pressure decreases, the balloon expands because the air inside pushes outward.

    In summary, the new air column length can be determined by applying the gas law relationship between pressure and volume while accounting for the hydrostatic pressure of the surrounding mercury.

    Option c – 16 cm

    A body of Mass 0.5 kg is whirled in a vertical circle at an angular frequency of 10 rad/s. If the radius of the circle is 0.5 m, what is the tension in the string when the body is at (A) the top of the circle (B) the bottom of the circle?

    (A) 10 N and 20 N

    (B) 20 N and 30 N

    (C) 30 N and 20 N

    (D) 40 N and 30 N

    Explanation:

    This question deals with the forces acting on a body moving in a vertical circular path and how the tension in the string changes depending on the position of the body along the circle.

    In circular motion, an object requires a centripetal force directed toward the center of the circular path. This force keeps the object moving along the circular trajectory. The magnitude of centripetal force is given by the relation F = mω2r, where m is the Mass of the body, ω is the angular frequency, and r is the radius of the circular path.

    When a body moves in a vertical circle, gravity also plays a role in determining the tension in the string. At the bottom of the circle, the tension must support the weight of the body and also provide the required centripetal force. At the top of the circle, gravity acts toward the center of the circle, which changes how the forces combine to provide the necessary centripetal force. Therefore, the tension at these two positions differs because gravity either adds to or subtracts from the required centripetal force.

    A common example is swinging a bucket of water in a vertical circle. The force in your hand changes depending on whether the bucket is at the top or bottom of the motion.

    In summary, the tension in the string at different points of the vertical circle depends on the centripetal force requirement and the direction of gravitational force relative to the motion.

    Option b – 20 N and 30 N

    The pilot of an aircraft who is not tied to his seat can loop a vertical circle in the air without falling out at the top of the loop. What is the minimum speed required so that he can successfully negotiate a loop of a radius of 4 km? ( ICSE Class 10 Physics Important Questions )

    (A) 200 m/s

    (B) 50 m/s

    (C) 100 m/s

    (D) 300 m/s

    Explanation:

    This question examines the minimum speed required for an aircraft to successfully perform a vertical loop without the pilot losing contact with the seat at the highest point of the loop.

    When an object moves in a vertical circular path, it must maintain sufficient centripetal acceleration to remain on that path. At the top of the loop, the centripetal force required for circular motion is directed toward the center of the circle. Both gravity and the normal force from the seat can contribute to this required centripetal force.

    To determine the minimum speed condition, consider the situation where the pilot is just about to lose contact with the seat. At that instant, the normal force becomes zero because the seat is no longer pushing on the pilot. Therefore, the only force acting toward the center of the circular path is the gravitational force. The condition for circular motion then becomes m v2 / r = mg. By simplifying this expression, the relationship between the required speed and the radius of the loop can be obtained.

    An everyday analogy is swinging a stone tied to a string in a vertical circle. If the speed becomes too low at the top, the string slackens and the stone falls.

    In summary, the minimum speed required occurs when gravity alone provides the necessary centripetal force to maintain circular motion at the top of the loop.

    Option a – 200 m/s

    The hour hand and the minute hand of a clock coincide at every relative Periodic time:

    (A) 11/12 hour

    (B) 12/11 hour

    (C) 11/6 hour

    (D) 12/24 hour

    Explanation:

    This question examines how often the hour hand and minute hand of a clock overlap while rotating at different angular speeds.

    In a clock, both hands rotate uniformly but with different angular velocities. The minute hand completes one full revolution in 60 minutes, whereas the hour hand completes one full revolution in 12 hours. Because their speeds differ, the minute hand gradually gains on the hour hand as time passes. The relative motion between the two hands determines how often they align.

    To analyze the situation, consider the angular speeds of the two hands. The minute hand moves faster than the hour hand, so the difference in their angular velocities determines how quickly the minute hand catches up to the hour hand. Each time the minute hand gains an angular displacement of 360° relative to the hour hand, the two hands coincide again. By calculating the relative angular speed and determining the time required for a full relative revolution, the interval between successive coincidences can be obtained.

    A simple analogy is two runners on a circular track where one runs faster than the other. Each time the faster runner laps the slower runner, they meet at the same point again.

    In summary, the interval between successive coincidences depends on the relative angular velocity between the hour hand and the minute hand of the clock.

    Option b – 12/11 hour

    In a rotor, a hollow vertical structure rotates about its axis as a person rests against the inner wall. At a particular speed of the rotor, the floor below the person is removed and the person hangs resting against the wall without any floor. It radius of the rotor is 2 m and the coefficient of static friction between the wall and the person is 0.2. Then the minimum speed at which the floor may be removed : ( ICSE Class 10 Physics Important Questions )

    (A) 100 m/s

    (B) 0.1 m/s

    (C) 1 m/s

    (D) 10 m/s

    Explanation:

    This question concerns the condition required to keep a person pressed against the wall of a rotating cylindrical rotor when the floor is removed.

    When the rotor spins, the person moves in circular motion along with the wall. To maintain this circular motion, a centripetal force is required, which is provided by the normal reaction force exerted by the wall on the person. This normal force pushes the person toward the center of the circular path.

    The friction between the person and the wall plays an important role in preventing the person from sliding downward under the influence of gravity. The frictional force acts upward along the wall and must be sufficient to balance the weight of the person. The maximum static friction is given by f = μN, where μ is the coefficient of static friction and N is the normal reaction. Since the normal reaction also provides the centripetal force required for circular motion, it is related to speed through N = m v2 / r. By combining these relationships and balancing forces vertically, the minimum speed required for the person to remain in place can be determined.

    A similar principle is used in amusement park rides where riders are held against rotating walls when the floor drops away.

    In summary, the required minimum speed is determined by balancing gravitational force with the maximum available friction created by the centripetal normal reaction.

    Option d – 10 m/s

    A cyclist moving with a speed of 6 m/s. As he approaches a circular turn on the road with of a radius 120 m he applied brakes and reduces his speed at a constant rate of 0.4 m/s². The magnitude of the NET acceleration of the cyclist on the circular turn is at :

    (A) 0.5 m/s²

    (B) 1 m/s²

    (C) 0.1 m/s²

    (D) 0.55 m/s²

    Explanation:

    This question examines the total acceleration experienced by an object moving along a circular path while simultaneously changing its speed.

    In circular motion, acceleration can arise from two different sources. One component is the centripetal acceleration, which is directed toward the center of the circular path and is responsible for changing the direction of motion. The second component is tangential acceleration, which occurs when the speed of the object changes along the path.

    To analyze the problem, first identify the centripetal acceleration using the relation ac = v2 / r, where v is the instantaneous speed and r is the radius of the circular path. The cyclist is also slowing down at a constant rate, which means a tangential acceleration acts along the direction opposite to motion. Because these two accelerations act perpendicular to each other, the total acceleration experienced by the cyclist is obtained by combining them vectorially using the Pythagorean relation.

    A good analogy is driving a car around a bend while simultaneously applying the brakes. The car experiences both inward acceleration due to turning and backward acceleration due to braking.

    In summary, the magnitude of the NET acceleration results from the combined effects of centripetal acceleration and tangential acceleration acting simultaneously.

    Option a – 0.5 m/s²

    A particle travels in a circle of radius 20 cm at a speed that uniformly increases. If the speed changes from 5 m/s to 6 m/s in 2 seconds, then angular acceleration is : ( ICSE Class 10 Physics Important Questions )

    (A) 5.2 rad/s²

    (B) 6.2 rad/s²

    (C) 2.5 rad/s²

    (D) 5 rad/s²

    Explanation:

    This question investigates the angular acceleration of a particle moving along a circular path when its speed increases uniformly with time.

    In circular motion, linear speed and angular velocity are related by the equation v = rω, where v is linear speed, r is the radius of the circular path, and ω is the angular velocity. When the linear speed of a particle changes with time, the angular velocity also changes accordingly.

    To analyze the situation, first determine how much the linear speed changes over the given time interval. Since the change occurs uniformly, the tangential acceleration remains constant. Using the relation between linear and angular quantities, the change in angular velocity can be calculated by dividing the change in linear speed by the radius of the circle. Angular acceleration is then obtained by dividing the change in angular velocity by the time interval. This process links the change in linear motion to the rotational motion of the particle.

    A helpful visualization is a point on the edge of a rotating wheel that gradually spins faster over time. As the speed increases, the rate of change of angular velocity represents angular acceleration.

    In summary, the angular acceleration depends on how quickly the particle’s linear speed changes relative to the radius of the circular path.

    Option c – 2.5 rad/s²

    The magnitude of the linear acceleration of a particle moving in a circle of radius 10 cm with uniform speed completing the circle in 4 seconds is :

    (A) 0.244 m/s²

    (B) 0.242 m/s²

    (C) 0.422 m/s²

    (D) 0.224 m/s²

    Explanation:

    This question focuses on determining the acceleration of a particle moving in uniform circular motion when the radius of the path and the time for one revolution are known.

    In uniform circular motion, even though the speed of the particle remains constant, the direction of velocity continuously changes. Because acceleration is defined as the rate of change of velocity, this continuous change in direction results in a centripetal acceleration directed toward the center of the circle.

    To analyze the problem, first determine the angular speed of the particle. The angular speed is related to the time period of rotation by the expression ω = 2π / T, where T is the time taken for one complete revolution. Once the angular speed is known, the centripetal acceleration can be found using the relation a = ω2r, where r is the radius of the circular path. This formula shows that centripetal acceleration increases with both angular speed and the radius of the motion.

    A familiar example is a stone tied to a string and swung in a circle. Even if the speed remains constant, the direction continuously changes, producing inward acceleration.

    In summary, the linear acceleration in uniform circular motion arises from the continuous change in direction of velocity and depends on the angular speed and radius of the circular path.

    Option a – 0.244 m/s²

    A particle moves in a circle of radius 20 cm. Its linear speed is given by v = 2t where t is in second and v in m/s. Radial and tangential acceleration at t = 3 seconds is :

    (A) 160 m/s², 1 m/s²

    (B) 4 m/s², 100 m/s²

    (C) 180 m/s², 2 m/s²

    (D) 120 m/s², 9 m/s²

    A particle travels along a circular path of radius 20 cm and its speed changes with time according to the relation v = 2t. The objective is to determine the radial and tangential accelerations at the instant t = 3 seconds while the particle continues its circular motion.

    In circular motion where speed varies with time, two types of accelerations appear simultaneously. Tangential acceleration occurs because the speed is changing along the path and is calculated using the relation at = dv/dt. Radial acceleration (centripetal acceleration) occurs because the direction of velocity continuously changes while the particle moves in the circle. It is given by ar = v2/r, where v is instantaneous speed and r is the radius of the circular path.

    To analyze the motion, first evaluate the instantaneous speed using the given expression v = 2t at t = 3 s. Then determine the tangential acceleration by differentiating the velocity expression with respect to time. After obtaining the speed, substitute it into the centripetal acceleration formula ar = v2/r. The radius must be converted into meters before substitution to maintain consistent units. Tangential acceleration describes how fast the speed changes, whereas radial acceleration represents the inward acceleration required to keep the particle moving along the circular path.

    A helpful comparison is a car moving around a circular track while pressing the accelerator. The increase in speed produces tangential acceleration, while the turning of the track creates radial acceleration toward the center.

    Thus, non-uniform circular motion involves two perpendicular acceleration components: one caused by the change in speed and the other caused by the change in direction of motion.

    Option c – 180 m/s², 2 m/s²

    A pulley one meter in diameter rotating at 600 rpm is brought to rest in 80 sec by a constant force of friction on its shaft. How many revolutions does it make before coming to rest?

    (A) 100 rev

    (B) 400 rev

    (C) 200 rev

    (D) 300 rev

    A pulley with a diameter of 1 m initially rotates at a speed of 600 revolutions per minute. Due to friction acting on the system, the pulley gradually slows down and finally stops after 80 seconds. The task is to determine the total number of revolutions completed before it comes to rest.

    When a rotating body slows down uniformly due to friction, it undergoes constant angular deceleration. Rotational motion follows equations similar to linear kinematics but with angular quantities. Angular velocity (ω), angular acceleration (α), and angular displacement (θ) are related through equations such as θ = ωt + ½αt2. When the body stops, the final angular velocity becomes zero.

    To solve the situation, the first step is converting the initial rotational speed from revolutions per minute into revolutions per second or radians per second, so that it matches the unit of time in seconds. Since the final angular velocity is zero after 80 seconds, angular acceleration can be determined from the relation between initial velocity, final velocity, and time. Once the angular acceleration is known, substitute the values into the angular displacement equation θ = ωt + ½αt2. This gives the total angular displacement during the deceleration period. If angular displacement is calculated in radians, it must be converted into revolutions to determine how many full turns the pulley makes before stopping.

    A similar situation can be observed when a ceiling fan is switched off. Even after the power is removed, the fan continues rotating several times before friction gradually brings it to rest.

    Therefore, by applying rotational kinematic relations under constant angular deceleration, the total number of revolutions made before stopping can be determined.

    Option b – 400 rev

    A particle of mass ‘m’ is moving in a circular path of constant radius ‘r’ such that centripetal acceleration is varying with time ‘t’ as K²rt² where K is a constant. The power delivered to the particle by the force acting on it is :

    (A) m² K² r² t²

    (B) mk² r² t

    (C) m K²rt²

    (D) m Kr²t

    A particle moves along a circular path of fixed radius r, but the centripetal acceleration is not constant. Instead, it varies with time according to the expression K²rt². The objective is to determine the power supplied to maintain this motion.

    In circular motion, centripetal acceleration is related to speed through the relation ac = v2/r. If centripetal acceleration varies with time, the speed of the particle must also change with time. power in mechanics is defined as the rate at which work is done or energy is transferred. It can also be expressed as P = F · v, where F is the force acting in the direction of motion and v is the instantaneous velocity.

    To analyze the motion, first compare the given expression for centripetal acceleration with the standard formula v2/r. By equating these expressions, the speed of the particle can be expressed as a function of time. Once the speed is known, kinetic energy of the particle can be written as KE = ½mv2. Since the velocity varies with time, the kinetic energy also changes with time. power delivered to the particle is obtained by differentiating kinetic energy with respect to time. This process links the changing centripetal acceleration to the rate at which energy must be supplied.

    A useful analogy is a rotating motor whose speed increases steadily with time. As the rotation speeds up, additional energy must continuously be supplied to maintain the increasing motion.

    Thus, by relating centripetal acceleration to velocity and then evaluating the rate of change of kinetic energy, the power delivered to the particle can be determined.

    Option b – mk² r² t

    A body of mass 1 kg is moving in a vertical circle with a speed of 3 m/s and has a tension of 18.8 N in a circular path of radius 1m. The position of the body is

    (A) Top of the circle

    (B) Bottom of the circle

    (C) Inclined at an angle of 45° with a horizontal diameter

    (D) Inclined at an angle of 45° with a vertical diameter

    A body of mass 1 kg is moving along a vertical circular path of radius 1 m. At a certain instant, its speed is 3 m/s and the tension in the string is measured as 18.8 N. The goal is to determine the position of the body in the circular path.

    In vertical circular motion, tension in the string varies depending on the position of the body because gravitational force contributes differently along the circular path. The required centripetal force for circular motion is provided by the combined effect of tension and the component of gravitational force acting toward the center.

    At different positions in the circle, the direction of gravity relative to the center changes. At the lowest point of the circle, gravity acts opposite to the centripetal direction, while at the highest point it acts toward the center. At intermediate positions, only a component of the gravitational force contributes to centripetal acceleration. The general relation for circular motion involves balancing the centripetal force requirement m v2/r with the forces acting along the radial direction. By comparing the calculated centripetal requirement with the given tension and considering how gravitational force contributes at various points in the circle, the specific position of the body can be identified.

    A simple visualization is a stone tied to a string and rotated in a vertical circle. The tension in the string changes continuously as the stone moves from bottom to top.

    Therefore, by analyzing the balance between tension, gravitational force, and centripetal requirement, the position of the body along the circular path can be determined.

    Option b – Bottom of the circle

    The kinetic energy of a particle moving with constant speed on a circular path of radius 20 m is 200 J. The centripetal force acts on the particle are:

    (A) 10 N

    (B) 100 N

    (C) 20 N

    (D) 200 N

    A particle moves with constant speed along a circular path of radius 20 m, and its kinetic energy is given as 200 J. The objective is to determine the centripetal force required to maintain this circular motion.

    In uniform circular motion, even though the speed remains constant, the direction of velocity continuously changes. Because of this change in direction, the particle experiences a centripetal acceleration directed toward the center of the circular path. The force responsible for producing this acceleration is known as the centripetal force and is given by F = mv2/r.

    Kinetic energy is related to the velocity of the particle through the relation KE = ½mv2. From this expression, the quantity mv2 can be obtained in terms of kinetic energy. Substituting this relation into the centripetal force formula allows the force to be expressed directly in terms of kinetic energy and the radius of the circular path. This approach eliminates the need to separately calculate velocity or mass because the required term already appears in the kinetic energy expression.

    A useful example is a stone tied to a string and rotated in a horizontal circle. The faster the stone moves or the smaller the circle becomes, the greater the inward force needed to keep it in circular motion.

    Thus, by relating kinetic energy to the centripetal force expression, the inward force acting on the particle can be determined from the given radius and energy.

    Option c – 20 N

    Tension in the string in a vertical circle of radius 1m in circular motion is 6.2 N at a certain position where speed is 4 m/s. If the mass of the stone attached to the string is 1 kg. The position is :

    (A) Top of circle

    (B) Bottom of the circle

    (C) Inclined at an angle of 45° with the horizontal diameter

    (D) Inclined at the angle of 45° with the vertical diameter

    A stone of mass 1 kg moves in a vertical circular path of radius 1 m while attached to a string. At a certain position during the motion, the speed of the stone is 4 m/s and the tension in the string is measured as 6.2 N. The goal is to determine the position of the stone along the circular path.

    In vertical circular motion, the tension in the string changes depending on the position of the body because gravitational force contributes differently to the centripetal force requirement. The centripetal force needed to keep the body moving in a circle is given by mv2/r. However, the forces acting toward the center depend on how gravity is oriented relative to the radius at that point.

    At the lowest point of the circle, gravity acts opposite to the centripetal direction and tension must overcome both gravity and provide the centripetal requirement. At the highest point, gravity acts toward the center and assists in providing the required centripetal force. At intermediate positions, only a component of the gravitational force contributes to the radial direction.

    By calculating the centripetal requirement using mv2/r and comparing it with the given tension, the contribution of gravity can be analyzed. This comparison helps determine whether gravity is assisting or opposing the centripetal force at that position, which identifies the location of the stone in the circular path.

    A familiar example is a bucket filled with water being swung in a vertical circle. The tension in the handle varies depending on whether the bucket is at the bottom, top, or somewhere in between.

    Therefore, analyzing the balance between tension, gravitational force, and centripetal requirement reveals the position of the stone along the vertical circular motion.

    Option a – Top of circle

    Does an automobile have a mass of 1000 kg what centripetal force is necessary for this vehicle to make a uniform 90° turn at 72 km/hr in a distance of 1570 m along the road?

    (A) 200 N

    (B) 400 N

    (C) 600 N

    (D) 800 N

    An automobile of mass 1000 kg moves along a circular road while making a 90° turn. The car travels at a speed of 72 km/hr and the radius of the curved path is 1570 m. The task is to determine the centripetal force required to keep the automobile moving along the curved path.

    Whenever a body moves in a circular path, its velocity direction keeps changing even if its speed remains constant. Because of this continuous change in direction, the body experiences an inward acceleration called centripetal acceleration. The force responsible for producing this inward acceleration is known as centripetal force and it acts toward the center of the circular path. The relation used for this force is F = mv2/r, where m is mass, v is speed, and r is the radius of the circular path.

    To analyze the situation, the speed must first be expressed in standard SI units because the formula requires velocity in meters per second. After converting the speed, substitute the values of mass, velocity, and radius into the centripetal force expression. The result represents the inward force needed to maintain circular motion. This force is typically provided by friction between the tires of the vehicle and the road surface.

    A common example is a car taking a curved highway turn. Even if the speed remains steady, the driver must rely on tire friction and road conditions to maintain the turn without skidding outward.

    Thus, the centripetal force required depends on the mass of the vehicle, the square of its speed v2, and the radius of the curved path.

    Option b – 400 N

    A curved road of a 100 m radius is banked at a correct angle for a given speed. If the speed is too halved, keeping the same banking angle the radius of the curvature of the road will be changed.

    (A) 35 m

    (B) 25 m

    (C) 45 m

    (D) 55 m

    A road is banked so that vehicles can safely move along a curved path of radius 100 m at a particular design speed. The question asks how the effective radius of curvature would change if the speed becomes half of that value while the banking angle remains unchanged.

    On a properly banked road, the horizontal component of the normal reaction provides the centripetal force required for circular motion. This arrangement allows vehicles to negotiate the curve without relying entirely on friction. The condition for safe turning depends on the relation between speed, radius of curvature, and the banking angle. For a given banking angle, the relationship between velocity and radius follows the proportional relation v2 ∝ r.

    To examine the situation, compare the original condition with the new speed. Since the banking angle does not change, the ratio between v2 and r must remain consistent. When the speed changes, the radius required for equilibrium must adjust accordingly. Because the speed appears as v2 in the relation, reducing the speed alters the radius by a factor related to the square of the speed ratio.

    A practical example can be seen on mountain roads where banking helps vehicles safely negotiate curves at certain speeds. If the vehicle moves much slower than the design speed, the same curvature behaves differently with respect to forces acting on the vehicle.

    Therefore, the new radius of curvature can be determined by applying the proportional relationship between speed squared and the radius for a fixed banking angle.

    Option b – 25 m

    A particle of mass m is in UCM of radius r and has momentum equal to P. Its KE is equal to

    (A) P²/2m

    (B) P²/2m

    (C) P/2m

    (D) P/m

    A particle of mass m moves along a circular path of radius r while maintaining uniform circular motion. The particle is described as having a momentum P, and the objective is to determine its kinetic energy using this information.

    Momentum is defined as the product of mass and velocity, expressed as p = mv. Kinetic energy, on the other hand, represents the energy associated with motion and is given by the relation KE = ½mv2. Even though the particle moves along a circular path, the speed remains constant in uniform circular motion, which means the magnitude of velocity remains unchanged while only its direction changes.

    To relate kinetic energy with momentum, the expression for velocity can be obtained from the momentum relation. Substituting this velocity into the kinetic energy equation allows the kinetic energy to be expressed entirely in terms of momentum and mass. This transformation is useful because it eliminates the need to know the velocity separately. The circular nature of motion mainly affects the direction of momentum rather than its magnitude.

    An analogy is a ball tied to a string and rotated in a horizontal circle. The ball maintains constant speed while continuously changing direction, meaning its kinetic energy remains constant during the motion.

    Thus, by expressing velocity in terms of momentum and substituting it into the kinetic energy formula, the required energy expression for the particle can be obtained.

    Option b – P²/2m

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    My name is Vamshi Krishna and I am from Kamareddy, a district in Telangana. I am a graduate and by profession, I am an android app developer and also interested in blogging.

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