# Newton’s Laws of Motion

In this article we will study about Newton’s law of motion . Here Newton’s laws of motion are given. There are three laws of motion of Newton which have been given in detail here.

## What are Newton’s laws of motion?

Newton’s laws of motion are three. which are given below.

### Newton’s laws of motion:-

(1) Newton’s First law of motion (Law of inertia)

(2) Newton’s second law of motion (Acceleration)

(3) The Third law of motion (Action and reaction)

## (1) Newton’s first law of motion (law of inertia)

Newton’s first law of motion is also called the law of inertia. Which are as follows:-

These laws are based on Galileo’s experimental observations. According to this law, “If an object is stationary, it will remain stationary and if it is in motion, it will remain in motion with a constant velocity unless an external force acts on it. It is also called the law of inertia.

Unbalanced force is necessary for an object to change from a stationary state to a state in motion with a uniform velocity, both are states of zero acceleration.

If the net external force acting on the object is zero, then its acceleration is zero.

Non-zero acceleration can occur only when an external unbalanced force, i.e., net external force, is acting on the object.

Explanation with example of Newton’s first law of motion :-

Newton’s first law defines inertia.

### (1) Inertia of rest :-

It is that property of the object due to which the object itself cannot change its state of rest.

It means that if an object is at rest, it remains at rest.

That is, it does not start the motion itself.

Example :- (i) If we place a coin on a smooth card board placed over a glass and

push the card board away at once with the help of fingers, then the card-board falls away

while the coin is at rest due to inertia. Cause it falls in the glass.

### (2) Inertia of Motion :-

The property of an object due to which it cannot change its state of uniform motion,

that is, an object doing uniform motion itself is neither accelerated nor decelerated.

Example :- (i) When a bus or train is stopped suddenly, then the passengers sitting in it tend to lean forward.

Because the lower part of their body comes to rest with the bus or train,

but the upper part remains in motion due to the inertia of motion.

### (3) Inertia of Direction :-

The property of an object due to which it cannot change the direction of its own motion is called inertia of the direction.

Example :- (1) When a car suddenly starts moving on a curved path, then the persons sitting inside start falling outwards.

## (2) Newton’s second law of motion

According to this law, the rate of change of momentum of an object is proportional to the external unbalanced force acting on it. And this change in momentum happens in the direction of the force.

Here K is the proportional constant. The value of which depends on the selected units.
Let us select the units in such a way that the value of K is obtained as 1.

F = m a

Therefore, the product of mass of an object and its acceleration is equal to the force acting on it.

And the direction of acceleration is in the direction of force.

### Example of Newton’s Second law of motion

(i) A player of cricket, while catching a ball coming at high speed, pulls his hand backwards.

The reason for this is that initially the ball is in motion and a retarding force is applied to stop the ball from the player’s hands.

Now if the player catches the ball suddenly, then due to the deceleration of the ball

too much force will have to be applied to stop the ball, which can cause injury to the player’s palm.

The slowdown will be less when the player moves his hand backward and gently catches the ball.

Therefore, the player will have to apply less force in catching the ball and there will be no possibility of injury to the player’s palm.

(ii) When a person jumps from a height on a hard floor, the velocity of the person immediately becomes zero. And the force exerted by the floor on the person is immense. causing injury to the person.

On the contrary, if a person jumps in the sand from the same height, then the

change in velocity happens gradually due to his feet getting stuck in the sand, so that the person does not get hurt due to the force acting on the floor.

## (3) Newton’s Third law of motion (Third)

Newton’s third law of motion is also called action-reaction law.

According to this law, “every action has a reaction of equal magnitude and opposite direction and action and reaction forces are applied on different bodies.

Example :-

(i) The weight of a body situated on a surface is downwards whereas the reaction

force R by the surface is applied upwards on the body.

(ii) Swimming is possible by Newton’s third law.

(iii) When a person walks on the earth, he presses the earth backwards by the oblique force F by the toes.

Earth also exerts the same force in the opposite direction.

This reaction force can be split into two right-angled components.

The horizontal component helps the person to move forward. Whereas the vertical component balances the weight of the person.