### GCSE Physics

Energy
Forces
Forces and Motion
Waves in Matter
Electricity
Magnetism and Electromagnetism
Particle Model of Matter
Atomic Structure
Space Physics

# Newtons First Law

Newton’s first law, also known as the law of inertia, states that an object will remain stationary or keep moving in a straight line unless an outside force interferes.

This principle applies to both stationary and moving objects.

• If a stationary object experiences a resultant force of zero, it remains stationary
• If a moving object has a resultant force of zero, it continues moving at a constant velocity – This means that it maintains the same speed, in the same direction.

The resultant force is the overall force acting on an object. In both cases, there is no resultant force acting on the objects, so their motion will not change.

## Example

1. The boulder is stationary because the net force acting on it is zero.

2. Balanced forces act on the boulder, so it remains stationary. The two men pushing the boulder from opposite sides create balanced forces.

3. Unbalanced forces act on the boulder, resulting in a non-zero resultant force, causing the boulder to accelerate.

## Example

1. The ball is stationary because the net force acting on it is zero.

2. The ball accelerates due to the unbalanced forces exerted by the foot.

3. Once the ball is set in motion, it continues in motion.

4. The ball encounters unbalanced forces when it hits the net, leading to a change in its speed and direction, causing it to slow down.

Quizzes