Newton’s first law of motion defines inertia as the inherent property of a body by virtue of which it resists any change in its state of rest or of uniform motion in a straight line on its own. This law is also known as the law of inertia.

Inertia can be categorised into three types:

(a) Inertia of rest

(b) Inertia of motion

(c) Inertia of direction

Examples:

(a) The carpet is beaten with a stick to remove the dust particles. Initially, both the carpet and the dust in it are at rest. When the carpet is shaken or beaten with a stick, the carpet is set into motion. Due to the inertia of rest, the dust particle tends to remain at rest. As a result, the dust particles fall off.

(b) The passengers in a bus tend to fall back when it starts suddenly. When a passenger is sitting in a stationary bus, both the bus and the passenger are at rest. When the bus starts suddenly, the lower part of the passenger’s body starts moving forward with the bus. However, the upper part of the passenger’s body tends to remain in the position of rest, due to the inertia of rest. As a result, the passengers fall or lean backwards.