Isaac Newton published his three laws of motion in 1687. They form the foundation of classical mechanics.

First Law — Law of Inertia

An object at rest stays at rest, and an object in motion stays in motion at the same speed and direction, unless acted on by an unbalanced force.

Second Law — Law of Acceleration

The acceleration of an object depends on the net force acting on it and its mass. Formula: F = ma

• F = net force (Newtons)
• m = mass (kilograms)
• a = acceleration (m/s²)

Third Law — Law of Action and Reaction

For every action there is an equal and opposite reaction. When you push against a wall, the wall pushes back on you with the same force.

Real-world examples:

• A rocket launches because exhaust gases push backward (action) and the rocket moves forward (reaction).
• A heavier shopping cart is harder to push than an empty one because of greater mass (Second Law).
• A book sitting on a table stays still because gravity down and normal force up are balanced (First Law).