TNPSC Physics Laws of Motion – 20 Important MCQ Practice

Every question you solve helps strengthen your understanding of Physics. This TNPSC Physics Laws of Motion quiz is designed to help you learn the fundamental principles of force, inertia, acceleration, momentum, and Newton’s Laws through exam-oriented MCQs. Attempt the quiz, review the explanations, and build the conceptual knowledge needed to score well in TNPSC and other competitive examinations.

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TNPSC Physics Laws of Motion Quiz 1 – Detailed Explanations

Learning from every answer is the key to long-term success. The detailed explanations below go beyond the correct option by explaining the scientific principles behind each question of this “TNPSC Physics – Laws of Motion Quiz 1”. Revising these concepts regularly will help you understand Laws of Motion more effectively and answer similar TNPSC questions with confidence.

1. Which scientist formulated the three laws of motion?

Sir Isaac Newton was an English mathematician and physicist who formulated the Three Laws of Motion in his book Philosophiæ Naturalis Principia Mathematica (1687). These laws explain how objects move when forces act upon them and form the foundation of classical mechanics. Newton’s work is widely applied in engineering, transportation, sports, and everyday life, making it one of the most important topics in TNPSC General Science.

Key Points

Sir Isaac Newton formulated the Three Laws of Motion.
Published in Principia Mathematica (1687).
Forms the foundation of classical mechanics.
Explains the relationship between force and motion.

✅ Correct Answer: B. Isaac Newton

2. Newton’s First Law of Motion is also known as:

Newton’s First Law states that an object remains at rest or continues to move with uniform velocity in a straight line unless acted upon by an external force. This property of resisting any change in the state of motion is called inertia, which is why the law is commonly known as the Law of Inertia. Everyday examples include passengers falling backward when a bus starts suddenly and dust separating from a carpet when it is shaken.

Key Points

Newton’s First Law is known as the Law of Inertia.
Inertia is the tendency to resist changes in motion.
An external force is required to change the state of rest or motion.
Greater mass results in greater inertia.

✅ Correct Answer: A. Law of inertia

3. Which quantity is defined as the product of mass and velocity?

Momentum is the quantity of motion possessed by an object and is calculated using the formula p = mv, where m is mass and v is velocity. It increases when either the mass or the velocity of an object increases. Since momentum has both magnitude and direction, it is classified as a vector quantity. The concept of momentum is widely used to study collisions and moving objects.

Key Points

Momentum = Mass × Velocity.
Formula: p = mv.
SI unit is kg·m/s.
Momentum is a vector quantity.

✅ Correct Answer: C. Momentum

4. The SI unit of force is:

Force is measured in the newton (N), the SI unit named after Sir Isaac Newton. One newton is defined as the force required to produce an acceleration of 1 m/s² in an object of mass 1 kilogram. Force is a vector quantity because it has both magnitude and direction.

Key Points

SI unit of force is newton (N).
Named after Sir Isaac Newton.
Formula: F = ma.
Force is a vector quantity.

✅ Correct Answer: B. Newton

5. According to Newton’s Second Law, force equals:

Newton’s Second Law explains the relationship between force, mass, and acceleration. It states that the net force acting on an object is equal to the product of its mass and acceleration, expressed as F = ma. This means that increasing the force increases acceleration, while increasing the mass reduces acceleration if the applied force remains constant.

Key Points

Formula: F = ma.
Force depends on mass and acceleration.
Greater force produces greater acceleration.
Greater mass reduces acceleration for the same force.

✅ Correct Answer: B. Mass × Acceleration

6. When a bus suddenly stops, passengers fall forward due to:

When a moving bus stops suddenly, the lower part of a passenger’s body stops with the bus, but the upper body continues moving forward due to inertia of motion. According to Newton’s First Law, an object in motion tends to remain in motion unless acted upon by an external force. This is why passengers lean or fall forward when a bus brakes suddenly.

Key Points

Example of inertia of motion.
Explained by Newton’s First Law.
Moving bodies resist stopping suddenly.
Common real-life application of inertia.

✅ Correct Answer: C. Inertia

7. Which of the following is an example of Newton’s Third Law?

Rocket propulsion is one of the best examples of Newton’s Third Law of Motion, which states that for every action there is an equal and opposite reaction. A rocket expels hot gases downward at high speed, and the reaction force pushes the rocket upward. This principle allows rockets to travel even in the vacuum of space, where there is no air.

Key Points

Rocket propulsion follows Newton’s Third Law.
Hot gases are expelled downward.
The reaction force moves the rocket upward.
Air is not required for rocket motion.

✅ Correct Answer: A. Rocket propulsion

8. The tendency of an object to resist a change in its motion is called:

Inertia is the natural property of every object to resist any change in its state of rest or motion. According to Newton’s First Law of Motion, an object remains at rest or continues moving with uniform velocity unless acted upon by an external force. The amount of inertia depends entirely on the object’s mass. Therefore, heavier objects have greater inertia and require more force to change their motion.

Key Points

Inertia is a property of matter.
It resists changes in rest or motion.
Inertia depends only on mass.
Explained by Newton’s First Law.

✅ Correct Answer: C. Inertia

9. Which of the following has the greatest inertia?

Inertia is directly proportional to mass. Among the given options, a truck has the greatest mass and therefore possesses the greatest inertia. This means it is more difficult to start, stop, or change the direction of a truck than a bicycle, car, or ball because it offers greater resistance to changes in motion.

Key Points

Greater mass means greater inertia.
Heavy vehicles require more force to accelerate or stop.
Inertia is independent of speed.
Mass alone determines inertia.

✅ Correct Answer: C. Truck

10. Momentum becomes zero when:

Momentum is calculated using the formula p = mv, where m is mass and v is velocity. If an object is at rest, its velocity becomes zero. Since anything multiplied by zero equals zero, the momentum also becomes zero. Even a heavy object has zero momentum if it is not moving.

Key Points

Momentum = Mass × Velocity.
Zero velocity results in zero momentum.
Momentum exists only when an object is moving.
SI unit is kg·m/s.

✅ Correct Answer: B. Velocity is zero

11. Action and reaction forces act on:

Newton’s Third Law of Motion states that for every action, there is an equal and opposite reaction. These two forces always act simultaneously on two different objects, not on the same object. For example, when you push a wall, you apply a force on the wall, and the wall applies an equal and opposite force on you.

Key Points

Action and reaction act on different bodies.
They are equal in magnitude.
They act in opposite directions.
They occur simultaneously.

✅ Correct Answer: B. Different objects

12. Which law explains the recoil of a gun?

When a bullet is fired, it moves forward with a large force. At the same time, the gun experiences an equal and opposite force, causing it to move backward. This backward movement is called recoil and is explained by Newton’s Third Law of Motion. The action is the forward motion of the bullet, while the reaction is the backward movement of the gun.

Key Points

Recoil is an application of Newton’s Third Law.
Action and reaction are equal and opposite.
Bullet moves forward; gun moves backward.
Common example in competitive exams.

✅ Correct Answer: C. Newton’s Third Law

13. If the mass of an object increases, its inertia will:

Inertia depends directly on the mass of an object. As the mass increases, the object’s resistance to changes in its state of motion also increases. Therefore, heavier objects require greater force to start moving, stop, or change direction compared to lighter objects.

Key Points

Inertia is directly proportional to mass.
Heavier objects have greater inertia.
More force is needed to change the motion of heavier bodies.
Inertia is not affected by speed.

✅ Correct Answer: B. Increase

14. The rate of change of momentum is equal to:

Newton’s Second Law of Motion states that the net force acting on an object is equal to the rate of change of its momentum. This means that when momentum changes rapidly, a greater force is produced. This principle is widely applied in vehicle safety systems, sports, and engineering.

Key Points

Force equals the rate of change of momentum.
Another form of Newton’s Second Law.
Momentum depends on mass and velocity.
SI unit of force is newton (N).

✅ Correct Answer: C. Force

15. When two bodies collide, the total momentum:

The Law of Conservation of Momentum states that in a closed system where no external force acts, the total momentum before a collision is equal to the total momentum after the collision. Although the momentum of individual objects may change, the total momentum of the system remains constant.

Key Points

Total momentum is conserved in a closed system.
External forces must be absent.
Individual momenta may change.
Total system momentum remains constant.

✅ Correct Answer: C. Remains constant

16. Which of the following is NOT a type of inertia?

There are three recognized types of inertia: inertia of rest, inertia of motion, and inertia of direction. These describe an object’s resistance to changes in its state of rest, motion, or direction. “Inertia of energy” is not a scientific term and is not classified as a type of inertia.

Key Points

Types of inertia:
- Inertia of Rest
- Inertia of Motion
- Inertia of Direction
Inertia of energy does not exist.
All types are explained by Newton’s First Law.

✅ Correct Answer: D. Inertia of energy

17. A cricket player moves his hands backward while catching a ball to:

When catching a fast-moving ball, a player moves the hands backward to increase the time taken to stop the ball. According to Newton’s Second Law, increasing the time of impact reduces the force experienced by the hands. This helps prevent injury and makes catching easier.

Key Points

Increasing stopping time reduces force.
Based on Newton’s Second Law.
Used in sports and vehicle safety.
Protects the hands from injury.

✅ Correct Answer: B. Decrease force

18. Force acting on an object can change its:

A force can produce several effects on an object. It can change the object’s speed by accelerating or slowing it down, alter its direction of motion, or even change its shape by compressing or stretching it. Therefore, force can affect an object’s speed, direction, and shape.

Key Points

Force can change speed.
Force can change direction.
Force can change shape.
Force can start or stop motion.

✅ Correct Answer: D. All of these

19. The SI unit of momentum is:

Momentum is the product of mass and velocity, so its SI unit is obtained by multiplying kilogram (kg) by metre per second (m/s). Therefore, the SI unit of momentum is kg·m/s. Momentum is a vector quantity because it has both magnitude and direction.

Key Points

Momentum = Mass × Velocity.
SI unit is kg·m/s.
Momentum is a vector quantity.
Greater mass or velocity increases momentum.

✅ Correct Answer: A. kg·m/s

20. Which law states that every action has an equal and opposite reaction?

Newton’s Third Law of Motion states that whenever one object exerts a force on another object, the second object exerts an equal force in the opposite direction on the first object. These action and reaction forces always occur together and act on different objects. This principle explains many everyday phenomena such as walking, swimming, rowing a boat, rocket propulsion, and gun recoil.

Key Points

Newton’s Third Law explains action and reaction.
Forces are equal in magnitude.
Forces act in opposite directions.
Action and reaction act on different objects.

✅ Correct Answer: C. Newton’s Third Law

Final Revision Tips

Before attempting the TNPSC exam, revise these important points from Laws of Motion:

Sir Isaac Newton formulated the Three Laws of Motion.
Newton’s First Law is known as the Law of Inertia.
Inertia is the tendency of a body to resist changes in its state of rest or motion.
Inertia depends only on mass—greater mass means greater inertia.
Newton’s Second Law: Force = Mass × Acceleration (F = ma).
Force is directly proportional to acceleration and inversely proportional to mass.
Newton’s Third Law: Every action has an equal and opposite reaction.
Momentum = Mass × Velocity (p = mv).
Force equals the rate of change of momentum.
Law of Conservation of Momentum: Total momentum remains constant in a closed system.
SI Unit of Force: Newton (N).
SI Unit of Momentum: kg·m/s.
Passengers fall forward when a bus stops suddenly due to inertia of motion.
Passengers fall backward when a bus starts suddenly due to inertia of rest.
Rocket propulsion, gun recoil, walking, swimming, and jumping from a boat are applications of Newton’s Third Law.
The three types of inertia are Inertia of Rest, Inertia of Motion, and Inertia of Direction.
A force can change the speed, direction, shape, or state of motion of an object.
Increasing the time of impact reduces the force, which is why cricketers move their hands backward while catching a ball.
Remember the common formulas:
- F = ma
- p = mv
Learn the real-life applications of all three laws, as TNPSC frequently asks concept-based questions.
Focus on understanding the concepts instead of memorizing facts to solve application-based MCQs confidently.

TNPSC Physics – Laws of Motion Quiz 1 (Basics)

TNPSC Physics Laws of Motion Quiz 1 – Detailed Explanations

1. Which scientist formulated the three laws of motion?

Final Revision Tips

Further Reading