First Law of Motion

Introduction

Objects around us do not change their state of motion on their own. A stationary object remains at rest, and a moving object continues to move unless something acts on it. This idea is explained by Newton’s First Law of Motion.

Newton’s First Law of Motion

Newton’s First Law of Motion states that:

"An object remains at rest or continues to move with uniform velocity in a straight line unless acted upon by an external unbalanced force."

Explanation

This law tells us that objects resist any change in their state of motion. A stationary object will not start moving on its own, and a moving object will not stop or change direction unless an external force acts on it.

If the forces acting on an object are balanced, the object will either remain at rest or move with constant velocity. Only an unbalanced force can change the state of motion.

Inertia

The tendency of an object to resist changes in its state of motion is called inertia.

Greater the mass of an object, greater is its inertia.

Types of Inertia

Inertia of Rest: A body at rest tends to remain at rest.
Inertia of Motion: A moving body tends to continue moving.
Inertia of Direction: A body resists change in its direction of motion.

Examples from Daily Life

A passenger falls backward when a bus suddenly starts due to inertia of rest.
A passenger falls forward when a moving bus suddenly stops due to inertia of motion.
Dust comes out when a carpet is beaten due to inertia of rest.
Passengers move sideways when a car takes a sharp turn due to inertia of direction.

Important Points

Objects resist change in their state of motion.
Balanced forces do not change motion.
Unbalanced forces change motion.
Inertia depends on mass.
This law is also called the law of inertia.

Conclusion

Newton’s First Law of Motion explains why objects remain at rest or continue moving unless acted upon by an external force. It introduces the important concept of inertia, which is fundamental to understanding motion and forces.