TNPSC Physics – Laws of Motion MCQ Quiz 5

Laws of Motion MCQ Quiz 5 – Key Concepts

This Laws of Motion MCQ set is designed to help you understand the core concepts of force, inertia, and motion in a simple way. These questions are important for TNPSC Physics MCQ, General Science Physics Quiz, and other competitive exams.

In this TNPSC Physics Online Quiz, each concept is explained with easy examples so you can clearly understand how the laws of motion work in real life. Practice these Questions to strengthen your basics and improve your exam performance. This Laws of Motion MCQ helps you understand key concepts for TNPSC exams.

Q1. When does a person feel heavier inside a lift?

A person standing in a lift feels heavier when the lift accelerates upward. This happens because the normal reaction force acting on the person increases due to upward acceleration.

When the lift moves up with acceleration, the apparent weight becomes greater than the actual weight. This is a direct application of Newton’s Second Law of Motion.

In contrast, when the lift moves downward, the apparent weight decreases.

A lift uses these principles to create variations in how weight is experienced without changing the actual mass.

Key Points:

• Upward acceleration increases apparent weight
• Normal reaction force increases
• Based on Newton’s Second Law
• Downward motion reduces apparent weight

Answer: Moves up with acceleration

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Q2. When a horse pulls a cart, the reaction force acts on which body?

When a horse pulls a cart, it exerts a forward force on the cart. According to Newton’s Third Law, every action has an equal and opposite reaction.

In this case, the cart also exerts an equal and opposite force on the horse. This reaction force acts backward on the horse, even though the cart moves forward.

This concept explains how motion occurs despite equal forces, as they act on different bodies.

Key Points:

• Action: Horse pulls the cart forward
• Reaction: Cart pulls the horse backward
• Forces are equal and opposite
• Act on different bodies

Answer: Cart on horse

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Q3. What is the acceleration produced when a force of 20 N acts on a body of mass 4 kg?

Acceleration of a body depends on the force applied and its mass. According to Newton’s Second Law, acceleration is calculated using the formula Force = mass × acceleration.

Here, when a force of 20 N acts on a mass of 4 kg, the acceleration can be found by dividing force by mass.

This type of numerical question is common in TNPSC exams and tests your understanding of basic physics formulas.

Key Points:

• Formula: Acceleration = Force / Mass
• Given: Force = 20 N, Mass = 4 kg
• Acceleration = 20 ÷ 4 = 5 m/s²
• Based on Newton’s Second Law

Answer: 5 m/s²

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Q4. Which of the following is an example of inertia of motion?

Inertia of motion refers to the tendency of a moving object to continue in its state of motion unless acted upon by an external force. This is explained by Newton’s First Law of Motion.

A person running continues to move forward even after crossing the finish line because the body resists stopping immediately.

This concept is commonly tested in TNPSC exams through real-life situations.

Key Points:

• Inertia of motion → object continues moving
• Explained by Newton’s First Law
• Motion does not stop instantly
• Requires external force to stop

Answer: A person continuing to run after crossing finish line

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Q5. The force required to stop a moving object depends on what?

The force needed to stop a moving object depends on its momentum. Momentum is the product of mass and velocity, and a higher momentum means the object is harder to stop.

Objects with greater mass or speed require more force to bring them to rest.

This concept is important in understanding motion and is frequently asked in TNPSC Physics MCQs.

Key Points:

• Momentum = mass × velocity
• Higher momentum → more force needed
• Depends on both mass and speed
• Important exam concept

Answer: Its momentum

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Q6. What happens when two equal and opposite forces act on a body?

When two forces of equal magnitude act in opposite directions on a body, they cancel each other. This results in no net force acting on the body.

According to Newton’s First Law, if no net force acts, the body either remains at rest or continues in uniform motion.

Such forces are called balanced forces.

Key Points:

• Equal and opposite forces cancel out
• Net force becomes zero
• Called balanced forces
• No change in motion

Answer: Remain in same state

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Q7. A ball thrown horizontally moves forward due to which reason?

When a ball is thrown horizontally, it continues to move forward because of the initial velocity given to it. This forward motion is independent of gravity, which acts downward.

According to Newton’s First Law, an object in motion continues in motion unless acted upon by an external force.

This explains why the ball keeps moving forward after being thrown.

Key Points:

• Forward motion due to initial velocity
• Gravity acts only downward
• Based on Newton’s First Law
• Motion continues unless stopped

Answer: Initial velocity

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Q8. Which of the following situations involves action and reaction on the same body?

According to Newton’s Third Law, action and reaction forces always act on two different bodies, not on the same body.

In all physical situations like walking, pushing, or rocket motion, the forces are equal and opposite but act on different objects.

Hence, there is no situation where both action and reaction act on the same body.

Key Points:

• Action and reaction are equal and opposite
• Always act on different bodies
• Cannot act on the same object
• Important TNPSC concept

Answer: None of these

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Q9. Why does a wall not move when a man pushes it?

When a man pushes a wall, he applies a force on it. According to Newton’s Third Law, the wall exerts an equal and opposite force on the man.

Since these forces balance each other and the wall is rigid, there is no motion.

This is an example of balanced forces where no change in motion occurs.

Key Points:

• Action: Man pushes wall
• Reaction: Wall pushes back
• Forces are balanced
• No motion occurs

Answer: Reaction force balances action

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Q10. The mass of an object is a measure of what?

Mass is a measure of inertia, which is the resistance of an object to any change in its state of motion. The greater the mass, the greater the inertia.

This means heavier objects are harder to start or stop compared to lighter objects.

This concept is directly related to Newton’s First Law of Motion.

Key Points:

• Mass measures inertia
• More mass → more resistance to motion change
• Related to Newton’s First Law
• Heavier objects are harder to move

Answer: Inertia

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Q11. Why are passengers pushed outward when a bus takes a sharp turn?

When a bus takes a sharp turn, the direction of motion changes suddenly. However, the bodies of passengers tend to continue in the original direction due to inertia.

This resistance to change in direction is called inertia of direction.

This is a common real-life example used in TNPSC exams.

Key Points:

• Inertia resists change in direction
• Body continues in original path
• Called inertia of direction
• Happens during sudden turns

Answer: Inertia

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Q12. What happens when a constant force acts on a body?

When a constant force acts on a body, it produces constant acceleration. As a result, the velocity of the body keeps increasing over time.

According to Newton’s Second Law, force is directly proportional to acceleration.

This leads to a continuous increase in velocity.

Key Points:

• Constant force → constant acceleration
• Velocity increases continuously
• Based on Newton’s Second Law
• Important exam concept

Answer: Increasing velocity

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Q13. What is the SI unit of impulse?

Impulse is defined as the change in momentum of an object. It is calculated as the product of force and time.

Since momentum has the unit kg·m/s, impulse also has the same unit.

This concept is important in understanding collisions and force applications.

Key Points:

• Impulse = change in momentum
• Unit of momentum = kg·m/s
• Same unit for impulse
• Related to force and time

Answer: kg·m/s

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Q14. Why does a heavier object require more force to move?

A heavier object has more mass, which means it has greater inertia. Inertia is the resistance to change in motion.

Because of this, more force is needed to move or accelerate a heavier object compared to a lighter one.

This concept is directly linked to Newton’s laws.

Key Points:

• More mass → more inertia
• Higher inertia resists motion
• Requires more force to move
• Important TNPSC concept

Answer: More inertia

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Q15. Which law explains why a person steps backward when catching a fast ball?

When catching a fast-moving ball, stepping backward increases the time taken to stop the ball. According to Newton’s Second Law, increasing the time reduces the force experienced.

This helps prevent injury by reducing the impact force.

This is a practical application of impulse and force.

Key Points:

• Increasing time reduces force
• Based on Newton’s Second Law
• Related to impulse concept
• Helps reduce impact

Answer: Second Law

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Q16. What happens to acceleration when force increases?

According to Newton’s Second Law, acceleration is directly proportional to the force applied on a body. This means that when the force increases, the acceleration also increases.

If the mass remains constant, doubling the force will double the acceleration.

This relationship is fundamental in solving physics problems.

Key Points:

• Acceleration ∝ Force
• More force → more acceleration
• Mass assumed constant
• Based on Newton’s Second Law

Answer: Increases

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Q17. Why does a moving object stop?

A moving object stops due to the action of external forces such as friction or air resistance. Without these forces, the object would continue moving indefinitely.

This is explained by Newton’s First Law of Motion.

Thus, an external force is necessary to stop motion.

Key Points:

• External force stops motion
• Friction is a common force
• Without force, motion continues
• Based on Newton’s First Law

Answer: External force

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Q18. Which of the following has the least inertia?

Inertia depends on the mass of an object. The smaller the mass, the lesser the inertia.

Among the given options, a feather has the least mass, so it has the least inertia.

This is a basic concept frequently asked in TNPSC exams.

Key Points:

• Inertia depends on mass
• Less mass → less inertia
• Feather has minimum mass
• Easy scoring question

Answer: Feather

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Q19. When is the motion of a body unchanged?

The motion of a body remains unchanged when the net force acting on it is zero. This happens when all the forces acting on the body are balanced.

According to Newton’s First Law, balanced forces do not change the state of motion.

The body will either remain at rest or move with constant velocity.

Key Points:

• Net force = 0
• Forces are balanced
• No change in motion
• Constant velocity or rest

Answer: Balanced forces act

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Q20. When does a body continue to move with uniform velocity?

A body continues to move with uniform velocity when there is no net force acting on it. This happens either when no force is applied or when all forces are balanced.

This is a direct application of Newton’s First Law.

Uniform velocity means constant speed in a straight line.

Key Points:

• No net force → uniform motion
• Balanced forces also result in no change
• Based on Newton’s First Law
• Velocity remains constant

Answer: Both A and B

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Real-Life Examples – Laws of Motion

1. Lift moving upward → You feel heavier due to increased reaction force
2. Horse pulling a cart → Cart pulls back on the horse (action–reaction)
3. Pushing a loaded trolley → More force gives more acceleration
4. Runner after finish line → Continues moving due to inertia
5. Stopping a fast bike → Requires more force due to higher momentum
6. Tug of war (equal force) → No movement due to balanced forces
7. Throwing a ball forward → Moves due to initial velocity
8. Rocket launch / walking → Action and reaction act on different bodies
9. Pushing a wall → Wall pushes back, so no movement
10. Moving a heavy cupboard → Harder due to more inertia
11. Bus taking a turn → Passengers pushed sideways (inertia)
12. Car accelerating → Speed increases due to constant force
13. Cricket bat hitting ball → Impulse changes momentum
14. Pushing a truck vs bicycle → Truck needs more force (more inertia)
15. Catching a cricket ball → Hands move backward to reduce force
16. Applying more force on a cycle → Cycle speeds up faster
17. Rolling ball stops → Stops due to friction (external force)
18. Feather vs stone → Feather is easier to move (less inertia)
19. Book resting on table → Balanced forces, no movement
20. Car moving at constant speed → Balanced forces maintain motion

Quick Revision Table – Laws of Motion (TNPSC)

Concept	Key Idea	Example
Inertia	Resistance to change in motion	Heavy objects are harder to move
Newton’s First Law	Body stays at rest or uniform motion	Passenger moves during sudden stop
Newton’s Second Law	Force = mass × acceleration	More force → more acceleration
Newton’s Third Law	Action = Reaction	Horse pulls cart, cart pulls horse
Momentum	Product of mass and velocity	Fast bike harder to stop
Impulse	Change in momentum	Bat hitting a cricket ball
Balanced Forces	Net force = 0	Book on table remains at rest
Unbalanced Forces	Causes acceleration	Car speeding up
Inertia of Motion	Object continues moving	Runner after finish line
Inertia of Rest	Object resists starting motion	Pushing a stationary car
Inertia of Direction	Resists change in direction	Passenger in turning bus
External Force	Required to stop motion	Friction stops moving ball
Initial Velocity	Causes forward motion	Thrown ball moves forward
Mass & Inertia	More mass → more inertia	Truck harder to move than bicycle
Uniform Motion	Constant velocity	Car moving at steady speed

Final Revision Tips

• Mass is a measure of inertia → more mass, more resistance to motion
• Balanced forces do not change motion (net force = 0)
• Unbalanced force produces acceleration
• Newton’s Second Law: more force → more acceleration
• Action and reaction forces act on different bodies
• Momentum depends on mass and velocity → higher momentum is harder to stop
• External forces like friction are required to stop motion
• Increasing time reduces force (important in catching objects)
• Uniform motion occurs when no net force acts
• Practice more Laws of Motion MCQ and TNPSC Physics MCQ regularly

For more detailed explanation, refer:
🔗 NCERT Class 11 Physics – Laws of Motion