## Physics

## Chapter - 3: Force

- 3.1 Inertia of Concept of Force - Newton's First Law
- 3.2 Nature of Fundamental Forces
- 3.3 Balanced and Unbalanced Forces
- 3.4 Momentum
- 3.5 Collision
- 3.6 Effect of Force on Motion: Newton's Second Law
- 3.7 Gravitational Force
- 3.8 Newton's Third Law
- 3.9 Frictional Force

Question Bank

## 3.1 Inertia of Concept of Force - Newton's First Law

- State Newton's first law.
- Explain why we never observe that a body in motion keeps its perpetual motion forever?
- What does inertia mean?
- What is inertia of rest?
- What is inertia of motion?
- Mass is the measurement of inertia? Explain.
- What is force?
- What is contact force?
- What is a non-contact force?
- Explain that the concept of inertia is found from Newton's first law.
- Which way does passenger lean when the moving bus suddenly breaks and why?

##
3.2 Nature of Fundamental Forces

- What is fundamental force?
- How many fundamental forces in nature and what are they?
- What do you mean by gravity?
- What do you mean by electromagnetic force?
- What do you mean by weak nuclear force?
- What do you mean by strong nuclear force?
- Discuss the comparative intensity of the fundamental forces.

## 3.3 Balanced and Unbalanced Forces

- What do you mean by balanced force?
- What do you mean by unbalanced force?

##
3.4 Momentum

- What is momentum?
- Determine the unit and dimension of momentum.
- What do you understand by momentum 200 kgm/s?
- Write the law of conservation of momentum.

## 3.5 Collision

- Write the law of conservation of momentum?
- Prove the law of conservation of momentum.
- Write the law of conservation of energy?
- Show that before the collision and after the collision total momentum is equal.
- Explain the necessity of force and motion in the case of safe journey.

##
3.6 Effect of Force on Motion: Newton's Second Law

- Write the second law of Newton.
- Prove that, F = ma.
- Write the unit and dimension of force.

## 3.7 Gravitational Force

- What is gravitational force?
- What is the value of the gravitational constant 'G'?

##
3.8 Newton's Third Law

- Write Newton's third law.
- Explain Newton's third law.

## 3.9 Frictional Force

- What is friction?
- What is frictional force?
- Explain the origin of friction.
- How many types of friction and what are they?
- What is static friction?
- What is sliding friction?
- What is rolling friction?
- What is fluid friction?
- Explain the effect of friction on the motion?
- Why there is a groove on the surface of the car tire?
- Explain how friction can be reduced?
- Explain how friction can be increased?
- Explain why friction is a necessary evil?

## Mathematical Problems

- What is the force to be applied to a mass of 50 kg to produce an acceleration of 4 ms
^{-2}? [Ans: 200 N]

- A boy pushes a box of mass 20 kg with a force of 50 N. What will be the acceleration of the box? [Ans: 2.5 ms
^{-2}]

- A force of 2000 N acts on a body of mass 20 kg for a time of 0.1 s. What is the change of momentum of the body? [Ans: 200 kgms
^{-1}]

- A bullet of mass 10 g was shot from a gun with a velocity of 500 ms-1. If the mass of the gun is 2 kg, find the backward velocity of the gun. [Ans: 2.5 ms
^{-1}]