The Laws of Motion were formulated by Sir Isaac Newton in the year 1687. They describe how and why objects move. These laws form the foundation of classical mechanics.
Table of Contents
1. Newton’s First Law of Motion (Law of Inertia)
Statement:
An object remains in its state of rest or of uniform motion in a straight line unless an external force acts on it.
Explanation
- Every object resists changes in its motion.
- This resistance is called inertia.
- A body will not start moving, stop moving, or change direction on its own.
Examples
- A passenger jerks forward when a moving bus stops suddenly (his body wants to remain in motion).
- A book on a table stays at rest unless someone pushes it.
2. Newton’s Second Law of Motion (Law of Acceleration)
Statement:
The rate of change of momentum of an object is directly proportional to the applied force and takes place in the direction of the force.
Mathematical Form
[ F = m a ]
Where:
- F = net force
- m = mass
- a = acceleration
Explanation
- Greater force → greater acceleration.
- Higher mass → lesser acceleration for the same force.
Examples
- Pushing an empty cart is easier than pushing a loaded cart.
- A cricket player lowers his hands while catching a ball to reduce force on his palms (reducing momentum gradually).
3. Newton’s Third Law of Motion (Action and Reaction)
Statement:
For every action, there is an equal and opposite reaction.
Explanation
- Forces always occur in pairs.
- If body A exerts a force on body B, body B exerts an equal and opposite force on A.
Examples
- A gun recoils backward when fired.
- A person jumps forward by pushing the ground backward.