**Q.1: Define force. Write down its formula and units. Also write down the
factors on which force depends?**

**Ans: FORCE:**

Force is that agent which changes or tends to change the state of rest or of motion of a body. It can also distort or tends to distort the shape of a body to which it is applied. It is denoted by F. It is a vector quantity.

Formula:

F =ma

Where

- F stand for force
- m stand for mass
- a Stand for acceleration

**Unit:**

In S.1. system, the unit of force is Newton (N).

**Newton:**

It can be defined as,

Force acting on a body is said to be of one Newton if it produces an acceleration of | rn/s in the body of mass 1 kg in the direction of the applied force.

**Factor On Which Force Depends:**

There are two factors on which force depends:

- Force is directly proportional to the mass of the body.
- It is directly proportional to acceleration produced in the body.

**Q.2: State the following laws?**

- Newton’s first law of motion
- Newton’s second law of motion
- Newton’s third law of motion
- Law of inertia

**Ans: NEWTON’S First Law OF MOTION:**

Every object continues its state of rest or of uniform motion in a straight tine unless it is acted upon by an external force which changes its state of rest or of uniform motion.

**NEWTON’S SECOND Law OF MOTION:**

When a force acts on a body, it produces acceleration in the body in its own direction. This acceleration is directly proportional to the magnitude of the applied force.

**NEWTON’S THIRD Law OF MOTION:**

To every action there is an equal but opposite reaction. Action and reaction do not act on the same body but act on two different bodies.

**Law OF INERTIA:**

The first law of motion is also called the law of inertia. Inertia is the property of a body due to which it resists against any change in its state of rest or of uniform motion.

**Q.3: Give any two examples of inertia?**

**Ans: INERTIA:**

**Example No. 1:**

If we put a coin on a card and place a card over a glass and flick away the card with the finger, the coin drops into the glass.

**Example No. 2:**

Suppose passengers are sitting in a bus. If it starts moving suddenly, the passengers will feel a jerk in the backward direction. it is because their bodies are in contact with the seat of the bus and come in motion with the motion of the bus while the upper parts of their bodies remain at rest due to inertia and so the passengers feet a jerk in the backward direction.

Similarly, if the bus is moving and stops suddenly the passengers will feel a jerk in the forward direction, it is also due to inertia.

**Q.4: States Newton’s second law of motion?**

**Ans: STATEMENT:**

The acceleration of a body is directly proportional to the force acting on it and inversely proportional to the mass of the body.

**Derivation Of F = ma:**

When a force is applied to a body, it produces acceleration in the body in the direction of force. This acceleration is directly proportional to the force. Mathematically,

axF —-—-—(i)

It means greater the force acting on the body, the greater will be acceleration, provided that mass of the body is constant.