In this world, we see many objects moving around us, for example, cars, buses, trucks, and bicycles moving on the road, aeroplanes flying in air and ships sailing on the sea, leaves falling from the trees and water flowing in the river. All these objects are changing their position with time. When an object changes its position with time, it is said to be in motion. In these examples, motion is easily visible to us. But in some cases, motion is not easily visible to us. For example, air moves in and out of our lungs and blood flows in our body. The moon moves around the earth, while the two together go around the sun. The sun itself with its planets travels through our own galaxy.
An object that does not change its position with time is said to be at rest, for example a book lying on a table.
In this lesson, you will learn how to describe motion. For this, we will develop the concepts of displacement, velocity and acceleration. You will also learn how these quantities are related to each other. For an object moving along a straight line with uniform acceleration, we will obtain simple equations (known as equations of motion) connecting these quantities with time.