Let's start with another important lesson which is 'motion'. Today we will learn what is motion? SI unit of motion and what is the symbol of motion?

Now assume, you are sitting on a bench in the park. Kind are playing football and suddenly the ball comes to you. Then you get up from the bench and kick the football towards the kids.

In this short story, when you are sitting on the bench you are at rest. When the football comes to you the ball is in motion and when you get up and kick the ball at that time you also come to motion from the rest position.

In this universe there are a lot of examples of motion even the universe itself undergoes in motion. You know that all the planets are revolving around the sun, the moon (the chanda mama) is revolving around the earth also in motion.

## What is Motion?

Well, we know when a body moves it undergoes motion. Is it the proper definition of motion?

## Definition of Motion

An object is said to be in motion if the body changes its position with respect to its surroundings in the given time.

Motion is always observed and measured with a point of reference. Let's try to understand motion with few examples,

### Examples of Motion

• An athlete running in a race continuously changes his position on the track with respect to the audience that watches him.
• The earth is continuously changing its position with respect to the sun which is at rest.

## Newton's Laws Of Motion

There are three laws of motion invented by Sir Isaac Newton. He is very famous for his discovery of the three laws of motion and the law of gravity.

First Law of Motion: An object at rest will stay at rest, and an object in motion will stay in motion at constant velocity unless an external force is applied on the object.

Second Law of Motion: The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass.

Newton's second law of motion represented by "force equals mass times acceleration (F = ma). Where, F is the force on the object, m is the mass of the object and a is the acceleration of the object.

Third Law of Motion: You must have heard the statement somewhere " for every action there is an equal and opposite reaction". Yes, this is the Newton's third law of motion.

## Types of Motion

There are various types of motion which can be differentiated by the force acting on the object. Some of the types of motion are described below.

### Q1. What is motion?

Ans: An object is said to be in motion if the body changes its position with respect to its surroundings in the given time.

### Q2.What causes motion?

Ans: A force causes motion.

### Q3.What is the SI unit of motion?

Ans: SI unit of motion is Meter per Second which can be expressed as m/sec.

### Q4.What are the examples of motion?

Ans: These are few examples of motion.
• The earth orbiting the sun.
• A simple pendulum.
• A moving car.
• A flying aeroplane.
• A rotating fan.
• A walking man.