The nucleus finally formed in the fusion of protons in the proton-proton cycle is that of
a. Hydrogen
b. Carbon
c. Helium
d. Nitrogen
Explanation: The proton-proton cycle is a sequence of nuclear fusion reactions that occur in extremely high-temperature environments like stellar cores. It begins when hydrogen nuclei (protons) overcome their electrostatic repulsion due to extremely high pressure and temperature. In the first steps, two protons fuse to form a deuterium nucleus, releasing energy in the form of positrons and neutrinos. Through subsequent fusion steps involving additional protons, intermediate nuclei are formed, gradually building up a more stable configuration. The process ultimately leads to the formation of a very stable Light nucleus composed of two protons and two neutrons, which represents a tightly bound configuration with high binding energy per nucleon. This final product is significant because it is more stable than the initial hydrogen nuclei, and the Mass difference is released as energy according to nuclear binding principles. The entire cycle is responsible for the enormous energy output of stars, where Mass is continuously converted into radiant energy. The stability of the final nucleus makes it a common endpoint of hydrogen fusion in stellar environments, and it plays a key role in sustaining stellar radiation over long periods of time.
Option c – Helium
Substances that have identical chemical properties but differ in atomic weights are called ( Engineering PhysicsVivaQuestions )
a. Isothermals
b. Isotopes
c. Isotropics
d. Isobars
Explanation: Atoms of the same element can sometimes exist in multiple forms that share identical chemical behavior because they contain the same number of protons and therefore have the same electronic configuration. However, these forms may differ in their Mass due to a variation in the number of neutrons present in their nuclei. Since chemical properties depend primarily on electron arrangement, these variations do not significantly affect reactivity or Bonding characteristics. The difference in neutron count leads to a change in atomic Mass, resulting in distinct Mass numbers while retaining the same atomic number. Such variations are naturally occurring and can be found across many elements in nature. These forms behave identically in chemical reactions, form the same compounds, and exhibit similar physical and chemical properties, but their masses differ, which can influence physical properties like density and diffusion rates. This concept is important in nuclear Physics and Chemistry because it explains why certain elements exist in multiple stable forms with slightly different masses but identical chemical behavior.
Explanation: The relationship between Mass and energy arises from the idea that Mass can be converted into an equivalent amount of energy under specific physical conditions. This concept comes from modern relativity theory, which links the inertia of a body with its energy content. In nuclear processes, even a small loss of Mass can correspond to a very large release of energy because the proportionality constant involves the square of the speed of Light, which is extremely large. This idea revolutionized Physics by showing that Mass is not absolutely conserved in isolation but is a form of stored energy. It helps explain phenomena like nuclear fission, fusion, and stellar energy production, where slight changes in mass result in enormous energy output. The equation also provides a fundamental bridge between classical mechanics and relativistic Physics, showing that energy and mass are interchangeable forms of the same physical quantity under extreme conditions.
Option d – Einstein
The first atomic reactor was constructed by ( Engineering PhysicsVivaQuestions )
a. Einstein
b. Goldstein
c. Fermi
d. Wein
Explanation: The development of the first controlled nuclear chain reaction marked a turning point in nuclear Physics. It involved assembling a carefully arranged structure of fissile material, moderator substances, and control mechanisms to sustain a steady release of energy from nuclear fission. The purpose was not explosive release but controlled energy production through a self-sustaining reaction. This experiment demonstrated that neutrons released during fission could trigger further fission events in a regulated manner, provided conditions such as critical mass and moderation were properly maintained. The success of this setup laid the foundation for nuclear reactors used today in power generation and research. It also proved that nuclear energy could be harnessed in a controlled Environment rather than being limited to uncontrolled reactions. The achievement required deep understanding of neutron behavior, chain reaction dynamics, and material properties that influence neutron absorption and scattering.
Option c – Fermi
The radiant energy from the sun is the result of
a. Combustion
b. Chemical reaction
c. Nuclear fission
d. Nuclear fusion
Explanation: The energy emitted by the sun originates from nuclear processes occurring in its extremely hot and dense core. Under such extreme conditions, Light atomic nuclei combine to form heavier nuclei through fusion reactions. During this transformation, a small portion of mass is converted into a large amount of energy, which is then released in the form of electromagnetic radiation. These reactions involve overcoming strong electrostatic repulsion between positively charged nuclei, which is possible only at very high temperatures and pressures. The energy released travels outward from the core and eventually reaches space as sunlight, supporting life and Climate on Earth. This continuous process maintains the sun’s stability over billions of years. The mechanism also explains why stars can emit energy for such long durations without quickly exhausting their fuel supply, as the efficiency of energy conversion in nuclear fusion is extremely high compared to chemical processes.
Option d – Nuclear fusion
The radius of the Earth is 6400 km. The linear velocity of a point on the equator is near: ( Engineering PhysicsVivaQuestions )
(A) 1000 km/hr
(B) 100 km/hr
(C) 1675 km/hr
(D) 800 km/hr
Explanation: A point located on the Earth’s equator undergoes circular motion due to Earth’s rotation about its axis. The linear speed of such a point depends on the angular speed of Earth and the radius of the planet at the equator. Since every point completes one full rotation in approximately 24 hours, the motion can be treated as uniform circular motion. The larger the radius of rotation, the higher the linear velocity for the same angular velocity. The equatorial region experiences the maximum linear speed because it lies at the greatest distance from the axis of rotation. This speed is significant in geophysical studies and affects phenomena such as atmospheric circulation and satellite launches. It also helps explain the variation in apparent gravitational effects across different latitudes due to rotational motion.
Option c – 1675 km/hr
Two racing cars of masses m1 and m₂ are moving in circles of radii r₁ and r2 respectively. Their speeds are such that each makes a complete circle in the same duration of time t. The ratio of the linear speed of the first to the second car is
(A) m1 : m2
(B) r1 : r2
(C) 1 : 1
(D) m₁r₁ : m₂r2 .
Explanation: When two objects move in circular paths and complete each revolution in the same time period, they share the same angular velocity. Linear velocity in circular motion depends on both angular velocity and radius of the path. Since angular velocity is identical for both, the difference in linear speeds arises solely due to differences in their radii of motion. A larger radius results in a greater linear speed for the same angular displacement per unit time. This relationship is fundamental in Rotational Dynamics and is widely used in analyzing systems like rotating wheels, satellites, and circular tracks. The proportionality between linear speed and radius ensures that objects farther from the axis of rotation cover more distance in the same time compared to those closer to it.
Option b – r1 : r2
The angular velocity of a wheel is 70 rad/s. If the radius of the wheel is 0.5 m, then its linear velocity will be : ( Engineering Physics VivaQuestions )
(A) 10 m/s
(B) 20 m/s
(C) 35 m/s
(D) 70 m/s
Explanation: In rotational motion, linear velocity of a point on a rotating body depends directly on both its angular velocity and its distance from the axis of rotation. The relationship shows that every point on a rigid rotating body has the same angular velocity, but points at different radii have different linear speeds. The farther a point is from the center, the greater its linear motion for the same angular rotation. This concept is widely applied in mechanical systems such as wheels, gears, and rotating machines. The proportionality ensures that rotational motion can be translated into linear motion effectively in engineering applications. This principle also explains why outer edges of rotating objects experience greater tangential speeds compared to points closer to the center.
Option c – 35 m/s
A particle moves in a circular path 0.4 m in radius with constant speed. If a particle makes 5 revolutions in each second of its motion the speed of the particle is :
(A) 10.6 m/s
(B) 11.2 m/s
(C) 12.56 m/s
(D) 13.6 m/s
Explanation: A particle moving in a circular path with constant speed covers a fixed circumference repeatedly in equal time intervals. The speed depends on how many complete revolutions it makes per second and the distance covered in one revolution, which is the circumference of the circle. Increasing the frequency of revolutions increases the total distance covered per unit time, thereby increasing speed. This type of motion is an example of uniform circular motion, where speed remains constant but direction changes continuously. The concept is widely used in rotational systems such as fans, wheels, and planetary motion. The relationship between frequency, radius, and speed helps in analyzing motion in engineering and physics applications involving circular paths.
Option c – 12.56 m/s
A stone of mass m is tied to a string of length L, and rotated in a circle with constant speed v, if the string is released the stone flies :
(A) Radially outward
(B) Radially inward
(C) Tangentially
(D) With an acceleration mv²/L
Explanation: When an object moves in a circular path, it continuously changes direction due to an inward force that maintains its curved motion. If this inward force suddenly disappears, the object no longer experiences any constraint to keep it in circular motion. As a result, it continues moving in the direction of its instantaneous velocity at the point of release. This direction is tangential to the circular path because velocity in circular motion is always tangent to the circle at every point. The subsequent motion is straight-line motion unless acted upon by another external force. This behavior demonstrates the principle of inertia, where an object maintains its state of motion unless influenced by an external force.
Option c – Tangentially
A cycle wheel is rotating with uniform angular velocity w. A graph is plotted between tangential velocities of different points on a spoke and their distance from the axis. This graph is a straight line :
(A) Parallel to the velocity axis
(B) Parallel to distance axis
(C) Intersecting both velocity and distance axes
(D) Passing through the origin with a slope w
Explanation: In uniform circular motion, every point on a rotating body shares the same angular velocity, but tangential velocity depends on the distance from the axis of rotation. This creates a direct proportional relationship between linear speed and radial distance. As distance from the axis increases, tangential velocity increases proportionally, resulting in a linear relationship when plotted graphically. The slope of this relationship represents angular velocity, which remains constant for the rigid body. This concept is fundamental in rotational kinematics and is used in analyzing rotating systems like discs, wheels, and turbines. It helps in understanding how different parts of a rotating object move at different linear speeds despite sharing the same rotational motion.
Option d – Passing through the origin with a slope w
If the centripetal force is cut, the body will fly away in a straight line, tangential to that point. The final path will be parabola due to the: ( Engineering Physics VivaQuestions )
Explanation: When an object moving in a circular path loses the force responsible for maintaining its curved trajectory, it no longer follows circular motion. Instead, it continues in a straight-line direction due to inertia, while simultaneously being influenced by gravity if acting vertically. The combination of uniform horizontal motion and constant vertical acceleration results in a curved trajectory. This type of motion is characteristic of projectile motion, where the path naturally takes a parabolic shape. The absence of inward force eliminates circular constraint, allowing gravitational influence to dominate vertical displacement while horizontal motion remains unaffected. This interaction of independent motions produces the characteristic curved path observed in such cases.
Option d – Gravitational force
A wheel rotates about an axis passing through the center and perpendicular to the plane with slowly increasing angular speed. It has :
(A) Radial velocity and radial acceleration
(B) Tangential velocity and radial acceleration
(C) Tangential velocity and tangential acceleration
(D) Tangential velocity and acceleration having both tangential and radial components
Explanation: When a rigid body rotates about a fixed axis and its angular speed is not constant but increasing gradually, the motion becomes an example of non-uniform circular motion. In such cases, the velocity of any point on the rotating body is always tangential to the circular path, but its magnitude keeps changing with time. Since angular speed is increasing, there must be an additional component of acceleration apart from the inward one responsible for changing direction. The inward component depends on the instantaneous angular speed, while the additional component arises due to the change in angular speed itself. This results in a combined acceleration that has two perpendicular components. Such motion is common in systems where motors gradually increase speed, like rotating discs or fans during startup.
Option d – Tangential velocity and acceleration having both tangential and radial components
A wheel completes 2000 revolutions to cover the 9.5 km distance, then the diameter of the wheel is : ( Engineering Physics VivaQuestions )
(A) 1.5 m
(B) 1.5 cm
(C) 7.5 m
(D) 7.5 cm
Explanation: When a wheel rolls without slipping, the linear distance covered is directly related to the number of rotations it makes and the circumference of the wheel. Each complete revolution corresponds to a distance equal to the circumference, which depends on the diameter of the wheel. By relating total distance traveled with total number of revolutions, the circumference can be determined. Once the circumference is known, the diameter can be found using the relationship between circumference and diameter of a circle. This concept is widely used in mechanics of rolling motion, where rotational motion is converted into linear displacement. It is also useful in real-life applications such as vehicle odometers and wheel-based measuring instruments.
Option a – 1.5 m
The extremity of the minute hand of a clock moves 20 times faster than that of the hour hand, the length of the minute hand is 10 cm then the length of the hour hand is :
(A) 1 cm
(B) 2 cm
(C) 3 cm
(D) 6 cm
Explanation: In circular motion, linear speed of a point depends on both angular speed and its distance from the center of rotation. Clock hands rotate with uniform angular speeds, where the minute hand completes one full rotation much faster than the hour hand. Because of this difference, even if the minute hand is longer or shorter, its tip generally moves faster due to higher angular velocity. The problem compares linear speeds of the tips of two rotating hands, linking their angular speeds with their lengths. By using proportional relationships between angular velocity and radius, one can relate their linear speeds. This is a direct application of rotational motion principles used in clocks and other timekeeping mechanisms.
Option d – 6 cm
The second hand of a watch has a length of 6 cm. The speed of the endpoint and magnitude of the difference of velocities at two perpendicular positions will be :
(A) 6.28 and 0 mm/s
(B) 8.88 and 4.44 mm/s
(C) 8.88 and 6.28 mm/s
(D) 6.28 and 8.88 mm/s
Explanation: The tip of a second hand moves in a circular path with constant angular speed, completing one full revolution in a fixed time interval. Linear speed depends on radius and angular velocity, so it remains constant for a given hand. However, velocity is a Vector quantity, meaning its direction changes continuously as the hand rotates. At different positions, even if speed remains the same, velocity Vectors can differ significantly. When two positions are perpendicular, the velocity Vectors form a right angle, and their difference depends on Vector subtraction principles. This concept highlights the difference between scalar speed and Vector velocity in rotational motion. It is commonly applied in analyzing circular motion of clocks and rotating machinery.
Option d – 6.28 and 8.88 mm/s
A motor car is traveling at 20 m/s on a circular curve of radius 100 m. It is increasing its speed at the rate of 5 m/s² what is its acceleration? : ( Engineering Physics VivaQuestions )
(A) 2 m/s²
(B) 4 m/s²
(C) 6.4 m/s²
(D) 9 m/s²
Explanation: When a vehicle moves along a curved path while simultaneously increasing its speed, it experiences two types of acceleration. One is directed toward the center of the circular path, arising due to continuous change in direction of motion. The other is along the direction of motion, arising due to change in speed. These two components act perpendicular to each other, and the resultant acceleration is obtained by combining them vectorially. This situation is common in real driving conditions where vehicles may not maintain constant speed while turning. The analysis of such motion is important in road safety and vehicle dynamics, especially in understanding how forces act during curved motion with acceleration.
Option c – 6.4 m/s²
An electric fan has blades of length 30 cm as measured from the axis of rotation. If the fan is rotating at 1200 rpm the acceleration of a point on the tip of the blade is about :
(A) 1600 m/s²
(B) 4740 m/s²
(C) 2370 m/s²
(D) 5055 m/s²
Explanation: A rotating fan blade undergoes circular motion, and any point on it experiences acceleration directed toward the center of rotation due to continuous change in direction. This inward acceleration depends on angular speed and the distance of the point from the axis. Higher rotational speeds produce significantly larger acceleration values at the tip of the blade. Since angular speed is often given in revolutions per minute, it must be converted into standard units for analysis. This concept is important in mechanical design because high rotational speeds can generate large stresses in materials. It explains why rotating machines require strong structural support to withstand inward forces at the outer edges.
Option b – 4740 m/s²
Two particles P and Q are located at distances rp and rQ respectively from the center of a rotating disc such that rp > rQ : ( Engineering Physics Viva Questions )
(A) Both P and Q have the same acceleration
(B) Both P and Q do not have the same acceleration
(C) P has greater acceleration than Q
(D) Q has greater acceleration than P
Explanation: In a rigid rotating body, all points share the same angular velocity, but their linear speeds depend on their distance from the axis. Acceleration in circular motion also depends on the radius, increasing with distance from the center. Therefore, points farther from the axis experience greater acceleration even though the rotational motion is shared. This difference arises because outer points cover larger circular paths in the same time. Such behavior is fundamental in rotational mechanics and explains why outer regions of rotating systems experience greater stress compared to inner regions. This principle is used in designing rotating machinery, discs, and wheels to ensure structural stability.
Option c – P has greater acceleration than Q
A car is traveling at 30 m/s on a circular road of a radius of 300 m. It is increasing its speed at the rate of 4 m/s². The acceleration of the car is :
(A) 3 m/s²
(B) 4 m/s²
(C) 5 m/s²
(D) 7 m/s²
Explanation: When a car moves along a curved path and its speed increases, its motion involves two simultaneous effects. The change in direction creates inward acceleration, while the change in speed produces forward acceleration. These two accelerations act perpendicular to each other, and the overall acceleration is obtained by combining them as Vectors. This situation is typical in real-world driving where vehicles rarely maintain constant speed while turning. Understanding both components is important for analyzing motion on curved roads and ensuring safe driving conditions. The resultant acceleration determines the NET effect experienced by the driver during such motion.
Option c – 5 m/s²
A particle of mass m is moving in a horizontal circle of radius r with a uniform speed v. When it moves from one point to a diametrically opposite point it: ( Engineering Physics Viva Questions )
(A) Kinetic energy changes by mv²/4
(B) Momentum does not changes
(C) Momentum changes by 2mv
(D) Kinetic energy changes by mv²
Explanation: In uniform circular motion, the speed of a particle remains constant while its direction continuously changes, leading to continuous change in velocity even if kinetic energy remains unchanged. When a particle moves to a diametrically opposite point on the circle, its velocity Vector undergoes a significant directional change of 180°, meaning the direction is exactly reversed along the same line of motion at that instant. Since kinetic energy depends only on speed, it remains unchanged throughout the motion. However, momentum, being a Vector quantity, changes because it depends on both magnitude and direction of velocity. At opposite points, the momentum Vectors are equal in magnitude but opposite in direction, leading to a complete reversal effect. This highlights the fundamental difference between scalar and Vector quantities in circular motion and emphasizes how direction plays a crucial role in momentum change even when speed is constant.
Option c – Momentum changes by 2mv
A particle revolves around a circular path with constant speed. The acceleration of the particle is :
(A) Along the circumference of the circle
(B) Along the tangent
(C) Along the radius
(D) Zero
Explanation: In uniform circular motion, even though the speed of the particle remains constant, the velocity continuously changes due to the change in direction. This continuous change in direction gives rise to acceleration, which is always directed toward the center of the circular path. This inward acceleration is responsible for keeping the particle in its circular trajectory and is essential for maintaining circular motion. Without this inward acceleration, the particle would move in a straight line due to inertia. The magnitude of this acceleration depends on the square of the speed and inversely on the radius of the path, meaning higher speeds or smaller radii result in stronger inward effects. This concept is fundamental in Rotational Dynamics and explains motion in systems such as planets, satellites, and rotating machines.
Option c – Along the radius
To enable a particle to describe a circular path, what should be the angle between its velocity and centripetal acceleration? ( Engineering Physics Viva Questions )
(A) 0°
(B) 45°
(C) 90°
(D) 180°
Explanation: In circular motion, velocity and acceleration play distinct roles in maintaining the motion of a particle along a curved path. The velocity Vector always lies tangential to the circular path, representing the instantaneous direction of motion. On the other hand, the acceleration responsible for circular motion acts radially inward toward the center of the circle. Since one is tangential and the other is radial, they are perpendicular to each other at every point of motion. This perpendicular relationship ensures that the acceleration continuously changes only the direction of velocity without altering its magnitude in uniform circular motion. This geometric relationship is fundamental in understanding how circular motion is sustained and is widely used in analyzing planetary motion, satellites, and mechanical rotation systems.
Option c – 90°
In an accelerated circular motion :
(A) Angular velocity remains constant
(B) Centripetal acceleration remains constant
(C) Kinetic energy remains constant
(D) Angular velocity, centripetal acceleration, kinetic energy changes
Explanation: In circular motion where the speed of the particle is not constant, both the magnitude and direction of velocity change simultaneously. This leads to two different components of acceleration acting at the same time. One component is responsible for changing the direction of motion and always acts toward the center of the circular path. The other component arises due to the change in speed along the tangent to the path. These two components are perpendicular to each other and together determine the resultant acceleration of the particle. Such motion occurs in real-life systems like accelerating vehicles on curves or rotating machinery during speed changes. The combination of these two accelerations explains the complex behavior of non-uniform circular motion.
Option d – Angular velocity, centripetal acceleration, kinetic energy changes
A body of mass 2 kg is attached to one end of a string and is resting on a smooth horizontal table. The other end of the string passes through a smooth hole in the table and carries another mass of 0.2 kg. The length of the string on the table is 0.8 m, then the number of revolutions per minute with which the body can revolve are :
(A) 0.17 rev/min
(B) 10.7 rev/min
(C) 10.6 rev/min
(D) 17 rev/min
Explanation: This system represents a combination of rotational motion and radial tension balance, where one mass moves in a circular path while another mass provides the required centripetal force through tension in the string. The rotating mass experiences an inward force that keeps it moving in a circle, and this force is supplied by the weight of the hanging mass. The balance between gravitational force and centripetal force determines the angular speed of rotation. Since the string passes through a smooth hole, friction is negligible, and the motion remains steady when forces are balanced. Such systems are useful in demonstrating the relationship between rotational motion and tension in strings and are commonly used in classical mechanics experiments involving uniform circular motion.
Option c – 10.6 rev/min
A long beam is spun at a constant speed of 1.75 rad/s. Astronaut is made to slowly walk along this beam from the axis of rotation, the distance at which he will experience a centrifugal acceleration equal to the acceleration due to gravity : ( Engineering Physics Viva Questions )
(A) 1.75 m
(B) 3.2 m
(C) 6.2 m
(D) 9.86 m
Explanation: In a rotating system, any point away from the axis experiences an outward effect due to rotational motion, often described in terms of centrifugal acceleration in a rotating reference frame. This acceleration depends on both the angular speed and the radial distance from the axis of rotation. As distance increases, the effect becomes stronger, meaning points farther from the center experience larger outward influence. When this acceleration equals gravitational acceleration, the outward and downward effects become comparable in magnitude. This condition is useful in analyzing rotating environments such as space stations or rotating beams where artificial gravity effects are studied. The relationship highlights how rotation can simulate gravitational-like effects depending on distance from the axis.
Option b – 3.2 m
A car is moving with a speed of 30 m/s on a circular track of radius 500 m. Its speed is increasing at the rate of 2 m/s² then its acceleration :
(A) 1.8 m/s²
(B) 2 m/s²
(C) 2.69 m/s²
(D) 3.2 m/s²
Explanation: When a car moves along a circular path and its speed changes, its motion involves two independent acceleration components. One component is directed toward the center of the circular path and arises due to continuous change in direction. The other component acts along the direction of motion and arises due to change in speed. These two components are perpendicular, and the total acceleration is obtained by combining them vectorially. This situation commonly occurs in real driving conditions where vehicles accelerate while turning. The resultant acceleration determines the NET effect experienced by the driver and is important for understanding vehicle stability and safety on curved roads.
Option c – 2.69 m/s²
A driver of a car traveling at high speed suddenly sees a board wall in front at a distance ‘s’. To avoid a collision he should :
(A) apply brakes
(B) turn the car sharply
(C) switch off the engine of the car
(D) close the eye
Explanation: When a vehicle is moving at high speed and an obstacle appears suddenly at a short distance, the available time to react and change motion becomes extremely limited. The driver must reduce the kinetic energy of the vehicle or change its trajectory depending on the situation. Since stopping distance depends on initial speed, braking capability, and road conditions, the safest approach is to minimize speed as quickly as possible. Braking converts kinetic energy into Heat through friction, reducing velocity gradually. At high speeds, stopping requires a much larger distance because kinetic energy increases with the square of speed. This makes timely response critical in preventing collisions. The concept highlights the importance of reaction time and braking efficiency in real-life driving safety scenarios.
Option a – apply brakes
The angular velocity of the rotating body of mass 4 kg has increased twice when the resultant force applied to it is increased by 48 N. Find the final centripetal acceleration :
(A) 4 m/s²
(B) 16 m/s²
(C) 1.6 m/s²
(D) 48 m/s²
Explanation: In rotational motion, centripetal force is responsible for keeping a body moving along a circular path and is directly related to angular velocity and radius of rotation. When angular velocity increases, the required inward force increases significantly because it depends on the square of angular speed. If angular velocity doubles, the inward requirement becomes four times larger. This relationship shows how sensitive rotational systems are to changes in speed. The force applied to maintain circular motion must therefore adjust accordingly. The resulting acceleration toward the center also increases with the square of angular velocity. This principle is widely used in analyzing rotating systems such as wheels, turbines, and planetary motion where small changes in speed lead to large changes in required inward force.
Option b – 16 m/s²
When the angular velocity of a uniform rotating body has increased thrice, the resultant forces applied to it increase by 60 N. Find the acceleration of the body, in two cases if the mass of the body is 3 kg :
(A) 2.5 m/s², 7.5 m/s²
(B) 7.5 m/s², 22.5 m/s²
(C) 5 m/s², 45 m/s²
(D) 2.5 m/s², 22.5 m/s²
Explanation: In circular motion, the inward force required to maintain rotation depends on both mass and centripetal acceleration. Since centripetal acceleration is proportional to the square of angular velocity, increasing angular velocity leads to a significant increase in required force. When angular velocity changes by a factor, acceleration changes by the square of that factor. This relationship allows comparison between two different rotational states. The mass of the body determines how much force is required to produce a given acceleration, but the underlying acceleration depends purely on rotational speed and radius. Such comparisons are important in mechanical systems where speed variations directly affect structural forces in rotating components.
Option d – 2.5 m/s², 22.5 m/s²
Which of the following keeps the body in UCM by changing its direction of velocity continuously :
(A) Tangential Acceleration
(B) Radial Acceleration
(C) Torque
(D) Couple
Explanation: Uniform circular motion requires a constant change in the direction of velocity while keeping its magnitude unchanged. This continuous change in direction is caused by an inward-directed influence that acts perpendicular to the velocity at every point. Without this inward influence, the object would move in a straight line due to inertia. The mechanism responsible ensures that the object remains constrained along a circular path by continuously redirecting its velocity Vector toward the center. This is a fundamental concept in Rotational Dynamics and is essential for understanding motion in systems like planets orbiting stars, electrons in magnetic fields, and objects tied to strings in circular motion.
Option b – Radial Acceleration
A van is moving at a speed of 108 km/hr on a level road, where the coefficient of friction between tires and the road is 0.5. For the safe driving of a van, the minimum radius of curvature of the road will be : (g = 10 m/s²)
(A) 80 m
(B) 40 m
(C) 180 m
(D) 20 m
Explanation: When a vehicle moves on a curved road, friction between tires and road surface provides the necessary inward force to prevent slipping outward. This frictional force acts as a substitute for centripetal force required in circular motion. The maximum available friction depends on the coefficient of friction and the normal reaction, which is related to the weight of the vehicle. For safe turning, the required centripetal force must not exceed the maximum frictional force. If speed increases, the required inward force increases significantly, demanding a larger radius of curvature for safety. This relationship is crucial in road design and vehicle dynamics, ensuring that vehicles can safely navigate curves without losing traction or stability.
Option c – 180 m
A cyclist going around a circle of radius 25 m completed its one revolution in 10 s the angle through which he leans inward is : (g = 9.8 m/s²)
(A) 90°
(B) 15°
(C) 45°
(D) 30°
Explanation: When a cyclist moves along a curved path, the tendency to move outward due to inertia is balanced by an inward force provided through the friction between tires and road. To maintain stability, the cyclist leans inward so that the resultant force passes through the center of mass. The angle of lean depends on the balance between gravitational force and required centripetal force. A faster speed or smaller radius increases the need for greater inward tilt. This leaning ensures that the resultant force remains aligned properly to prevent toppling. This concept is widely used in cycling, motorbike racing, and banking of roads for safe turning at higher speeds.
Option c – 45°
A motorcyclist is moving round a circular track of radius 600 m. The track is 1m wide. If his speed is 72 km/hr. How much circular track must be lifted to Bank the track? (g = 9.8 m/s²)
(A) 10 cm
(B) 6 m
(C) 6.78 cm
(D) 8.33 cm
Explanation:banking of roads is used to reduce reliance on friction by tilting the surface so that a component of the normal reaction provides the required centripetal force. When a vehicle moves along a curved path, it tends to slip outward due to inertia, and banking helps counteract this effect. The required banking depends on speed, radius of curvature, and gravitational acceleration. A properly banked road ensures that vehicles can turn safely even at higher speeds without depending entirely on friction. This principle is widely applied in designing highways, Railway tracks, and race circuits to enhance safety and stability during curved motion.
Option c – 6.78 cm
A disc is rotating at a speed of 72 rpm. A coin is kept at a distance of 10 cm from the center of the disc. What must be the coefficient of friction between the disc and the coin so that the coin will not slide? (g = 9.8 m/s²)
(A) 0.4
(B) 0.48
(C) 0.25
(D) 0.57
Explanation: When an object rests on a rotating surface, friction provides the necessary inward force to keep it from sliding outward. As the surface rotates, the object tends to move away from the center due to inertia, but static friction counteracts this tendency. The maximum friction available depends on the coefficient of friction and normal force. For the object to remain stationary relative to the rotating surface, the required centripetal force must not exceed maximum frictional force. This condition allows determination of the minimum coefficient of friction needed. Such analysis is important in understanding stability of objects on rotating platforms and in mechanical systems involving rotating discs.
Option d – 0.57
The angle which the bicycle and its rider make with vertical when going round at 18 km/hr around a road of radius 10 m on level ground : (g = 9.8 m/s²)
(A) 16° 19′
(B) 14° 19′
(C) 24° 19′
(D) 45° 19′
Explanation: When a bicycle moves along a curved path, it must generate an inward force to maintain circular motion. This force is achieved by leaning the system such that the resultant of gravitational force and required inward force passes through the Base of support. The angle of lean depends on speed and radius of curvature. Higher speeds require greater inward force, leading to a larger lean angle. This ensures that the cyclist does not topple outward due to inertia. The concept is widely used in cycling dynamics and helps explain how riders maintain balance while turning at different speeds on curved tracks.
Option b – 14° 19′
A cyclist moves in a circular track of a radius of 50 m. If the coefficient of friction is 0.4 then the maximum velocity with which a cyclist takes a turn without leaning inward is : (g = 9.8 m/s²)
(A) 14 m/s
(B) 10 m/s
(C) 7 m/s
(D) 20 m/s
Explanation: When a cyclist moves along a circular path without leaning inward, the entire requirement for circular motion must be supplied by friction between the tyres and the road. This friction acts toward the centre of the circle and provides the necessary inward force needed to keep the motion curved. If the speed increases beyond a certain limit, the required inward force becomes greater than the maximum available friction, causing the cyclist to slip outward. The maximum safe speed is therefore determined by balancing the required centripetal force with limiting frictional force. This condition depends on the coefficient of friction, gravitational force, and radius of the circular path. A larger radius allows higher speeds, while lower friction reduces the safe speed limit. This concept is important in understanding vehicle stability on flat curves and in road safety design.
Option a – 14 m/s
The maximum safe speed of the vehicle on a circular track is 15 km/hr, when a track becomes wet maximum safe speed is 10 km/hr. The ratio of the coefficient of friction of dry track to wet track is :
(A) 9 : 4
(B) 3 : 2
(C) 2 : 3
(D) 4 : 9
Explanation: On a flat curved road, friction between the tyres and the surface provides the necessary centripetal force required for circular motion. The maximum possible speed before slipping depends directly on the coefficient of friction, which determines how much inward force can be generated without loss of contact. When the road becomes wet, the frictional force decreases due to reduced grip, lowering the safe turning speed. Since centripetal force requirement depends on speed squared, the relationship between speed and coefficient of friction can be used to compare conditions. A higher friction surface allows higher safe speeds, while a lower friction surface reduces stability during turning. This principle is widely used in road safety analysis, especially under varying weather conditions.
Option a – 9 : 4
The string of a conical pendulum will become horizontal when :
(A) the Speed of revolution is zero
(B) the Speed of revolution is almost infinite
(C) the Speed of revolution is low
(D) the Speed of revolution is very low
Explanation: In a conical pendulum, a mass attached to a string moves in a horizontal circular path while the string traces out a cone shape. The tension in the string has two components: one balancing the weight of the mass and the other providing the centripetal force required for circular motion. As the speed of rotation increases, the required centripetal force increases, causing the string to tilt further away from the vertical direction. When the speed becomes extremely large, the centripetal force requirement becomes dominant compared to the weight component. In such a case, the string approaches a nearly horizontal position as it must provide almost entirely inward force for circular motion. This situation represents an extreme case of Rotational Dynamics in constrained circular motion.
Option b – the Speed of revolution is almost infinite
A sphere of mass 0.2 kg is attached to an inextensible string of length 130 cm whose upper end is fixed to the ceiling. The sphere is made to describe a horizontal circle of radius 0.5 m then the tension in the string :
(A) 1.96 N
(B) 2 N
(C) 2.12N
(D) 5.2 N
Explanation: In circular motion, tension in the string plays a crucial role in providing the required centripetal force that keeps the object moving along a curved path. When a mass moves in a horizontal circle, the tension has both vertical and horizontal components. The vertical component balances the weight of the object, while the horizontal component provides the inward force needed for circular motion. The geometry of the system depends on the length of the string and the radius of the circular path, which determines the angle of inclination. By combining force balance in vertical and horizontal directions, the magnitude of tension can be determined. This type of motion is commonly seen in conical pendulum systems and rotating objects attached to strings.
Option c – 2.12N
The circumference of a circular track is 1.256 km. The maximum speed at which the vehicle is safe on this track is 20 m/s then the angle of banking is :
(A) 1° 24′
(B) 2° 50′
(C) 11° 32′
(D) 45⁰
Explanation:banking of roads is designed to help vehicles negotiate curves safely by reducing reliance on friction. When a vehicle moves on a curved road, it requires an inward force to maintain circular motion. On a banked surface, part of the normal reaction force is tilted inward, contributing to this required force. The angle of banking depends on the speed of the vehicle and the radius of curvature of the road. A properly designed banking angle ensures that vehicles can turn safely even at high speeds without slipping outward. This principle is widely used in highways, flyovers, and race tracks where vehicles move at significant speeds while turning.
Option c – 11° 32′
A simple pendulum is suspended from the roof of a carriage of a Railway train, if the train goes around the curve of radius 50 m at 45 km/hr then the angle to which the string inclined vertically is near:
(A) 2⁰
(B) 9⁰
(C) 18⁰
(D) 30⁰
Explanation: When a train moves along a curved path, passengers or suspended objects inside experience an apparent outward effect due to inertia. A simple pendulum suspended inside the train will tilt away from the vertical direction because the effective force acting on it is a combination of gravitational force and the inertial effect due to circular motion. The pendulum aligns itself along the resultant of these two effects, which determines its angle of inclination. The angle depends on the speed of the train and the radius of curvature of the track. Higher speeds or smaller radii increase the tilt. This phenomenon helps in understanding non-inertial reference frames and apparent forces in rotating or accelerating systems.
Option c – 18⁰
The radius of curvature of a Railway line at a place is 500 m and the safe speed limit is 54 km/hr then the angle of banking for this safe speed :
(A) 1⁰
(B) 4.5⁰
(C) 2⁰
(D) 2.6⁰
Explanation: In Railway track design, banking is used to reduce lateral stress on wheels and improve stability when trains move along curves. When a train moves on a curved track, it experiences an outward tendency due to inertia, which must be balanced by an inward force. Instead of relying entirely on friction, the track is inclined so that a component of gravitational force helps provide the required centripetal force. The banking angle depends on the speed of the train and the radius of curvature of the track. Proper banking ensures smooth and safe motion of trains without excessive wear on rails or risk of derailment. This concept is essential in Railway engineering design.
Option d – 2.6⁰
For a banked road of the radius of curvature, 600 m with a safe speed of 72 km/hr elevation of the outer edge above the inner edge is if the road 10 m broad :
(A) 0.67 cm
(B) 6.7 cm
(C) 67 cm
(D) 6.7 m
Explanation: On a banked road, the outer edge is raised relative to the inner edge to help vehicles take turns safely. This height difference creates a sloped surface, allowing part of the gravitational force to act toward the center of the circular path. The required elevation depends on the speed of the vehicle, radius of curvature, and width of the road. Faster speeds require greater banking to provide sufficient inward force. This design reduces dependence on friction and improves safety, especially under varying road conditions. Banking is widely used in highways and race tracks where vehicles move at high speeds while turning continuously.
Option c – 67 cm
A train has to negotiate a curve of radius 400 m with a speed of 48 km/hr if the distance between the rails is 1 m thus the outer rail should be raised above the inner rail by a distance of
(A) 4.5 cm
(B) 9 cm
(C) 15 cm
(D) 45 cm
Explanation: When a train negotiates a curved track, the outward centrifugal tendency must be balanced to ensure safe and stable motion. This is achieved by raising the outer rail compared to the inner rail, creating a banked track. The required elevation depends on train speed, radius of curvature, and distance between the rails. Proper elevation ensures that the resultant force passes through the center of mass of the train, reducing lateral stress on wheels and preventing derailment. This principle is crucial in Railway engineering for maintaining safety and comfort during curved motion at moderate to high speeds.
Option a – 4.5 cm
A man with his hands in his pockets is standing in a bus, which is moving in a horizontal curve of a radius of 50 m with a speed of 7 m/s. How far from the vertical he must lean to keep the balance :
(A) 45⁰
(B) 30⁰
(C) 18⁰
(D) 5° 42′
Explanation: When a bus moves along a curved path, passengers inside experience a sideways effect due to inertia. A person standing inside the bus must lean inward to maintain balance. This is because the resultant of gravitational force and the inertial effect due to circular motion must pass through the Base of support. The required lean angle depends on speed and radius of curvature. Higher speed increases the outward tendency, requiring a greater inward lean to maintain equilibrium. This situation illustrates non-inertial reference frames where apparent forces arise due to acceleration of the system.
Option d – 5° 42′
A scooterist is moving around the circular track of a radius of 480 m. The track is 1 m wide, If his speed is 72 km/hr, how much outer edge of the track is lifted. to Bank the track for him : (g = 10 m/s²)
(A) 10 cm
(B) 8.3 cm
(C) 16.6 cm
(D) 4.1 cm
Explanation: When a vehicle moves along a curved path, banking of the road helps in providing the required centripetal force by tilting the surface. The outer edge is raised so that a component of gravitational force assists in turning the vehicle safely. The required height difference depends on the speed of the vehicle, radius of curvature, and width of the track. Proper banking reduces reliance on friction and enhances stability during motion. This concept is widely applied in designing curved roads and tracks for safe movement of vehicles at higher speeds.
Option b – 8.3 cm
Keeping the angle of banking to be the same, if the maximum speed with which a vehicle can travel on the curved road is increased by 10%. What should be the increase in the radius of curvature of the curve from 20 m?
(A) 10 m
(B) 8 m
(C) 4.2 m
(D) 6.85 m
Explanation: In a banked road, the relationship between speed, radius, and banking angle is governed by conditions of equilibrium during circular motion. If the banking angle remains constant, any change in speed must be compensated by a corresponding change in radius to maintain safe turning conditions. Since centripetal force requirement depends on the square of speed, even a small increase in speed leads to a noticeable change in required radius. This relationship is important in road design and ensures that vehicles can maintain stable motion without slipping or overturning when speed conditions change.
Option c – 4.2 m
The maximum speed with which a car can be safely driven along a curved road of a radius of 30 m and banked at 30° with horizontal :
(A) 130 m/s
(B) 1.303 m/s
(C) 14.00 m/s
(D) 13.03 m/s
Explanation: When a vehicle moves along a banked curved road, the normal reaction from the road surface can be resolved into two components. One component acts vertically upward and balances the weight of the vehicle, while the other component provides the necessary inward force required for circular motion. This design reduces reliance on friction and allows safe turning even at higher speeds. The maximum safe speed depends on the radius of curvature, the banking angle, and gravitational acceleration. A larger banking angle allows greater contribution of the normal force toward centripetal requirement, enabling higher speeds. This principle is widely applied in highway curves, flyovers, and race tracks to ensure stability and safety during motion along curved paths.
Option d – 13.03 m/s
A road is banked with an angle of 0.01 radian. If the radius of the road is 80 m, then the safe speed for the drive will be : (g = 10 m/s²)
(A) 2.828 m/s
(B) 3.828 m/s
(C) 4.828 m/s
(D) 5.828 m/s
Explanation: Banking of roads helps vehicles negotiate curves safely by providing part of the required centripetal force through the normal reaction of the road surface. When a road is slightly inclined, the normal force is tilted, producing a horizontal component that acts toward the center of curvature. This reduces dependence on friction and improves safety. The safe speed depends on the angle of banking, radius of curvature, and gravitational acceleration. For small angles, the sine and tangent of the angle are nearly equal, simplifying calculations. This relationship is widely used in designing roads where vehicles must maintain stability while turning at controlled speeds without slipping outward or inward.
Option a – 2.828 m/s
A boy on a cycle pedals around a circle of radius 20 m at a speed of 20 m/s. The combined mass of the boy and the cycle is 90 kg. The angle that the cycle makes vertical so that he may not fall : (g = 9.8 m/s²)
(A) 60.25 °
(B) 63.90 °
(C) 26.12 °
(D) 30.00 °
Explanation: When a cyclist moves in a circular path, the body tends to move outward due to inertia, while the friction between tyres and road provides the necessary inward force. To maintain balance, the cyclist must lean inward so that the resultant of gravitational force and required centripetal force passes through the Base of support. The lean angle depends on the ratio of centripetal force to weight, which is determined by speed and radius of motion. Higher speed increases the need for inward tilt, while larger radius reduces it. This balance ensures that the cyclist does not topple while taking a turn. This principle is widely used in cycling dynamics and motorbike racing for stability during curved motion.
Option b – 63.90 °
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