Laws of Motion MCQ for NEET

Explanation:
This question asks you to compare how friction varies when a car moves over different surfaces and arrange them from the least friction to the greatest. Friction depends on the nature and roughness of the surfaces in contact. Smooth or slippery surfaces offer less resistance, while rough and uneven surfaces provide greater resistance to motion. The interaction between tyres and road texture plays a key role in determining grip and motion stability.

To solve this, think about how each road type affects tyre contact. Muddy roads are usually soft and slippery, reducing friction. Tar roads provide moderate grip due to their relatively smoother finish. Concrete roads are harder and slightly rougher, increasing friction further. Gravel roads consist of loose, uneven particles that create maximum resistance due to irregular contact and displacement of stones.

Imagine pushing a box over different surfaces. It moves easily on a polished floor but requires more effort on sand or gravel. Similarly, cars experience varying resistance depending on the road type.

In short, friction increases as the surface becomes rougher and less uniform, affecting the ease of motion and control of the vehicle.

Explanation:
This question focuses on understanding inertia, a fundamental property of Matter that describes how objects behave when forces act on them. Inertia is the natural tendency of an object to resist any change in its current state, whether it is at rest or moving. It is directly related to the Mass of the object—the greater the Mass, the greater the inertia.

To reason this out, consider different scenarios. A stationary object does not start moving unless a force is applied. Similarly, a moving object continues in the same direction and speed unless acted upon by an external force. Even changing direction requires force because the object resists deviation from its path. These behaviors all arise from inertia.

A simple example is when a bus suddenly starts or stops. Passengers tend to jerk backward or forward because their bodies resist the change in motion. This clearly demonstrates inertia in everyday life.

Overall, inertia explains why objects maintain their existing state and oppose changes, forming the basis of motion laws in Physics.

Explanation:
This question examines the condition under which an object maintains uniform motion without any change in speed or direction. According to basic principles of motion, an object continues in its state unless influenced by an external factor. The idea highlights the relationship between motion and forces acting on the object.

To understand this, consider the role of forces. When multiple forces act on an object and cancel each other out, the NET effect becomes zero. In such a case, there is no change in velocity, meaning both speed and direction remain constant. However, if any unbalanced force acts, it causes acceleration, which changes motion.

For example, a hockey puck sliding on a smooth ice surface continues moving for a long distance because friction is minimal and no significant force opposes its motion. If friction increases, it slows down.

Thus, uniform motion persists only when no unbalanced force acts, ensuring that the object’s velocity remains unchanged over time.

Explanation:
This question focuses on the relationship among Newton’s three laws of motion and whether one can be derived from another. These laws describe how objects move and interact with forces, forming the foundation of classical mechanics.

Each law explains a different aspect of motion. The first law introduces the concept of inertia, the second law quantifies force and acceleration, and the third law explains interaction forces between bodies. While they are interconnected and consistent with each other, they describe distinct principles.

When analyzing them, one finds that none of the laws can be completely derived from the others. Each law is based on independent observations and experiments. However, they complement one another and together provide a complete description of motion.

Think of them like three pillars supporting a structure. Removing one weakens the understanding of motion, but no single pillar can fully replace the others.

In summary, Newton’s laws are independent yet interrelated principles that collectively explain how forces influence motion.

Explanation:
This question explores the practical use of Newton’s second law of motion in understanding physical quantities. The law establishes a relationship between force, Mass, and acceleration, making it a key tool in analyzing motion.

According to the law, the rate of change of momentum of an object is proportional to the applied force and occurs in the direction of that force. In simpler terms, when a force acts on an object, it causes acceleration depending on the object’s Mass.

To apply this concept, consider pushing objects of different masses with the same force. A lighter object accelerates more, while a heavier one accelerates less. This shows how force influences motion quantitatively.

For instance, when a car engine exerts force, it accelerates the vehicle. Engineers use this principle to calculate how much force is needed to achieve a desired motion.

Thus, Newton’s second law helps relate force with the resulting change in motion, providing a mathematical way to study dynamics.

Explanation:
This question deals with the phenomenon of recoil, where a cannon moves backward after firing a projectile. It highlights the interaction between two bodies when forces are applied.

When the cannon fires, gases expand rapidly and push the projectile forward. At the same time, an equal and opposite force acts on the cannon, causing it to move backward. These forces act simultaneously and are equal in magnitude but opposite in direction.

To understand this better, imagine standing on a skateboard and throwing a heavy ball forward. You will roll backward due to the reaction force. The same principle applies to the cannon.

This interaction demonstrates how forces always occur in pairs during interactions. The motion of the cannon is not due to a single force but due to the mutual forces between the cannon and the projectile.

In summary, recoil occurs due to equal and opposite forces acting during the firing process, leading to motion in opposite directions.

Explanation:
This question connects Newton’s third law with a fundamental conservation principle in Physics. The third law states that for every action, there is an equal and opposite reaction, which governs interactions between objects.

When two bodies interact, the forces they exert on each other are equal and opposite. These forces act over the same time interval, resulting in equal and opposite changes in momentum. As a result, the total momentum of the system remains unchanged.

To visualize this, consider two skaters pushing off each other. Both move in opposite directions, but the overall momentum before and after remains balanced.

This principle is widely used in analyzing collisions, explosions, and propulsion systems like rockets. It ensures that even though individual objects may change motion, the total momentum of the system is conserved.

Thus, Newton’s third law naturally leads to the idea that total momentum remains constant in an isolated system.

Explanation:
This question explores how rockets are able to move in space where there is no air for pushing against. The explanation lies in fundamental laws of motion and conservation principles.

A rocket works by expelling gases at high speed in one direction. As these gases are pushed backward, the rocket experiences an equal and opposite push forward. This interaction ensures that the total momentum of the system remains constant.

Even in the vacuum of space, this principle holds because the rocket does not rely on external surfaces. Instead, it carries its own fuel and produces thrust internally.

For example, when air is released from a balloon, it moves in the opposite direction. Rockets use a controlled and continuous version of this effect.

In summary, rocket motion is governed by the conservation principle where the backward motion of gases results in forward motion of the rocket.

Explanation:
This question focuses on identifying a physical quantity that combines Mass and velocity. This concept is fundamental in understanding motion and how objects behave when forces act on them.

Mass represents how much Matter an object contains, while velocity describes how fast and in what direction it is moving. When these two are combined, they provide a measure of how difficult it is to stop a moving object.

To understand this, consider a truck and a bicycle moving at the same speed. The truck is harder to stop because it has greater Mass, even though velocity is the same. This combined effect is what the question refers to.

In real life, this concept is important in collisions, where heavier or faster objects have a greater impact.

Thus, multiplying mass and velocity gives a quantity that reflects both motion and resistance to stopping, making it a key concept in dynamics.

Explanation:
This question is based on a fundamental principle that connects force and momentum. It highlights how changes in motion are influenced by applied forces.

Momentum depends on both mass and velocity. When a force acts on an object, it changes its velocity, thereby changing its momentum. The faster this change occurs, the greater the influence of the force.

To reason this out, consider kicking a football. A stronger kick changes the ball’s motion more rapidly, indicating a larger force. If the same force acts for a longer time, the overall change in momentum increases.

This concept forms the basis of many real-life situations, such as airbags in cars, which increase the time of impact to reduce force.

In summary, the rate of change of momentum depends on how strongly and in what manner a force is applied to an object.

Explanation:
This question deals with forces acting on an object at rest and how they balance each other. When an object is placed on a surface, it experiences gravitational force downward and a supporting force upward.

The downward force is due to the weight of the object. In response, the table exerts an upward force known as the normal reaction. For the object to remain at rest, these forces must balance each other.

If the upward force were less, the object would accelerate downward. If it were more, the object would move upward. Since the book remains stationary, the forces must be equal in magnitude and opposite in direction.

A simple analogy is a person standing still on the ground—the ground supports the person with an equal upward force.

Thus, equilibrium occurs when opposing forces cancel out, keeping the object at rest.

Explanation:
This question examines the condition under which an object stays at rest. It involves understanding how forces interact and balance each other.

An object may have several forces acting on it at the same time. However, if these forces are equal in magnitude and opposite in direction, they cancel out, resulting in no NET force. In such a situation, the object does not accelerate and remains stationary.

For example, a book on a table experiences gravitational force downward and normal force upward. These forces balance perfectly, so the book does not move.

It is important to note that the presence of forces does not necessarily cause motion. Only unbalanced forces lead to changes in motion.

In summary, a stationary object indicates that all forces acting on it are balanced, resulting in zero NET effect and no change in its state.

Explanation:
This question explores how the human body responds to sudden changes in motion. It is based on the concept that different parts of a body may react differently when motion begins abruptly.

When the horse starts moving forward suddenly, the lower part of the rider’s body in contact with the horse begins to move along with it. However, the upper part of the body tends to remain in its original state due to resistance to change. This creates a backward motion relative to the horse.

To understand this, imagine standing in a bus that suddenly starts. Your feet move forward with the bus, but your upper body lags behind momentarily. This causes you to tilt backward.

This effect is not due to any external pull but due to the body’s natural resistance to sudden changes in motion.

In summary, the backward fall occurs because different parts of the body respond differently to sudden acceleration, creating a temporary imbalance.

Explanation:
This question focuses on what happens when a moving person suddenly comes into contact with a stationary surface. It highlights how motion continues even when part of the body stops.

When a person jumps off a moving bus, their feet come in contact with the ground and tend to stop quickly due to friction. However, the upper part of the body continues moving forward with the same speed it had while on the bus. This difference in motion causes the person to fall forward.

To visualize this, think of running and suddenly stopping your feet while your body is still in motion—you will lurch forward. The same effect occurs here.

This phenomenon shows that motion does not stop instantly for all parts of the body at the same time.

In summary, the forward fall happens because part of the body stops abruptly while the rest continues moving, leading to imbalance.

Explanation:
This question involves understanding how force and time together influence the change in motion of an object. It is based on the relationship between force, time, and momentum.

When a force acts on an object over a certain duration, it changes the object’s velocity, thereby changing its momentum. The longer the force acts, the greater the overall effect on motion.

To analyze this, consider that applying a steady force continuously pushes the object, increasing its motion over time. Even if the force is small, a longer duration can result in a significant change.

For example, gently pushing a trolley for a long time can make it move faster than giving it a quick push.

This concept is important in understanding impulses in real-life situations like collisions and braking systems.

In summary, the change in motion depends on both how strong the force is and how long it is applied.

Explanation:
This question examines the physical principle that allows a person to move through water. It involves interaction between the swimmer and the surrounding Fluid.

When a swimmer pushes water backward with their hands and feet, the water exerts an equal and opposite force on the swimmer, pushing them forward. This interaction between the swimmer and water enables motion.

To understand this better, imagine pushing against a wall while standing on a skateboard—you move in the opposite direction. Similarly, pushing water backward results in forward movement.

This principle is not limited to swimming; it also applies to rowing boats and flying birds.

In summary, movement in water occurs due to mutual forces between the swimmer and water, resulting in motion in the opposite direction of the applied push.

Explanation:
This question deals with motion in a frictionless or nearly frictionless Environment. On a frozen lake, there is very little resistance between the person and the surface.

In such a situation, walking normally is difficult because there is not enough friction to push against the ground. However, the person can still move by pushing an object or throwing something in the opposite direction.

When the person exerts a force in one direction, an equal and opposite force acts on them, causing movement in the other direction. This allows motion even without friction.

For example, astronauts in space move by pushing objects or expelling gas, despite the absence of a Solid surface.

In summary, motion can still occur in low-friction environments through interaction forces that produce movement in opposite directions.

Explanation:
This question connects the unit of force with the effect of gravity on mass. It helps in understanding how force is defined in practical terms.

Force is related to mass and acceleration. On Earth, objects experience acceleration due to gravity, which gives them weight. The force required to hold an object is related to how strongly gravity pulls it downward.

To reason this out, consider that heavier objects require more force to hold because gravity acts more strongly on them. Lighter objects require less force.

For instance, holding a small apple requires less effort than holding a heavy bag because of the difference in mass and resulting gravitational force.

This concept helps define standard units in Physics and makes calculations consistent.

In summary, force can be understood in terms of how much mass it can support under gravitational influence.

Explanation:
This question focuses on identifying the direction of frictional force during motion. Friction is a resistive force that arises when two surfaces interact.

Whenever an object moves or tries to move over a surface, friction opposes that motion. It acts along the surface of contact and always resists the relative motion between surfaces.

To understand this, imagine sliding a book across a table. The frictional force acts opposite to the direction in which you push the book, slowing it down.

Even when an object is at rest, friction acts in a direction that prevents motion from starting. Thus, its role is always to oppose movement or attempted movement.

In summary, friction is a resistive force that always acts against motion, helping control and stabilize movement.

Explanation:
This question examines methods to decrease friction between surfaces. Reducing friction is important in improving efficiency and minimizing wear and tear.

Friction depends on surface roughness and the nature of contact. Smoother surfaces reduce irregularities, leading to less resistance. Similarly, lubricants create a thin layer between surfaces, preventing direct contact and reducing friction.

To reason this out, consider sliding a heavy object. It is easier on a polished floor than on a rough surface. Adding oil or grease further reduces resistance.

In machines, lubrication is widely used to improve performance and reduce Heat generation.

In summary, friction can be minimized by making surfaces smoother or by introducing substances that reduce direct contact between them.

Explanation:
This question highlights how the human body reacts to sudden acceleration in a moving vehicle. It demonstrates a fundamental principle related to motion.

When the bus accelerates forward, the lower part of the passenger’s body moves with the bus. However, the upper part tends to remain in its original state momentarily, causing the person to fall backward relative to the bus.

This can be observed when standing in a bus or train that starts suddenly. You feel a backward jerk because your body resists the sudden change in motion.

The effect is not due to any backward force but due to resistance to change in motion.

In summary, this situation illustrates how objects resist sudden changes in their state of motion, leading to observable effects in everyday life.

Explanation:
This question explores the relationship between the unit of momentum and other physical quantities. It involves understanding how different units in Physics are interconnected.

Momentum is defined as the product of mass and velocity. Its unit is therefore derived from the units of these quantities. Another concept, impulse, is defined as the product of force and time, and it represents the change in momentum.

When analyzed dimensionally, both momentum and impulse share the same unit, even though they arise from different contexts.

For example, applying a force over a period of time changes the motion of an object, linking these two quantities closely.

In summary, the unit of momentum corresponds to another physical quantity that measures the effect of force over time, showing a deep connection in mechanics.

Explanation:
This question examines how force affects the motion of an object with a given mass. It is based on the relationship between force, mass, and the resulting change in motion.

According to fundamental principles, when a force is applied to an object, it produces acceleration. The amount of acceleration depends on how large the force is and how massive the object is. A smaller mass experiences a greater change in motion for the same force compared to a larger mass.

To reason this out, imagine pushing a Light cart and a heavy cart with the same effort. The lighter one speeds up more quickly, showing a greater change in motion.

This relationship is widely used in Physics to predict motion in systems ranging from vehicles to projectiles. It forms the basis for defining standard units of force.

In summary, applying a force to a given mass produces a predictable change in motion, depending on the balance between force and mass.

Explanation:
This question focuses on understanding what happens when all forces acting on a moving object cancel each other out. It is a key idea in describing motion under balanced conditions.

When forces acting on an object are balanced, the NET force becomes zero. In such a situation, there is no acceleration, meaning the object does not change its velocity. Since velocity includes both speed and direction, both remain constant.

To understand this, think of a car moving on a straight road at steady speed. The engine provides forward force, while friction and air resistance oppose it. When these forces balance, the car continues moving without speeding up or slowing down.

This principle explains why objects can continue moving without continuous acceleration.

In summary, when no NET force acts on a moving object, its motion remains unchanged, maintaining a constant velocity.

Explanation:
This question explores why a moving object eventually comes to rest after the applied force is removed. It highlights the role of opposing forces in motion.

When the hockey ball is pushed, it gains motion due to the applied force. However, once the push stops, other forces such as friction between the ball and the surface begin to act. These forces oppose the motion and gradually reduce the speed of the ball.

To understand this, imagine sliding a book across a table. It eventually stops because friction resists its motion, even though no one is pushing it anymore.

This shows that continuous motion is not possible in the presence of opposing forces unless another force keeps the object moving.

In summary, the slowing down of the hockey ball occurs because resistive forces act against its motion, eventually bringing it to rest.