Newton's First Law

Key Stage 4

Meaning

Newton's First Law states that "An object in motion will tend to stay in motion and an object at rest will tend to stay at rest unless an unbalanced force acts upon it."

About Newton's First Law

Newton's First Law describes the fact that:

If the resultant force on an object is zero then it will continue to move at a constant velocity.

If the resultant force on an object is not zero then an object will accelerate (change speed or direction).

This means that if an object is observed changing speed or direction then there must be an unbalanced force acting on it.