Newton Laws of Motion

First Law (Law of Inertia)

An object stays at rest, or keeps moving at a constant speed in a straight line, unless a force acts on it. Example: passengers jerk forward when a bus stops suddenly.

Second Law

The acceleration of an object depends on the force applied and its mass. In formula form: Force = mass × acceleration (F = ma). A bigger force gives a bigger acceleration.

Third Law

For every action there is an equal and opposite reaction. Example: when you jump, you push the ground down and the ground pushes you up.

Key Points

• Force is measured in newtons (N).
• Inertia depends on mass: heavier objects are harder to move or stop.
• Action and reaction forces act on different objects.