Newton's first and third laws

Learn about Newton's first and third law.

This lesson includes:

  • one video
  • two activities

Learn

Sir Isaac Newton was a very intelligent man.

During the 17th Century, he developed three laws of motion that govern how all objects move.

In this lesson you will look at the first and third laws.

Newton's first law

According to Newton's First Law of motion, an object remains in the same state of motion unless a resultant force acts on it.

If the resultant force on an object is zero, this means:

  • a stationary object stays stationary
  • a moving object continues to move at the same speed and in the same direction

For example:

When a car travels at a constant speed, the driving force from the engine is balanced by resistive forces such as air resistance and friction in the car's moving parts.

The resultant force on the car is zero.

Newton's third law

Now watch this short film where Jon Chase explains Newton's third law of motion.

Newton's third law states:

For every action, there is an equal and opposite reaction.

This means, if you push on something (action) it pushes back (reaction).

For example:

On a racing car the wheel tries to push the road backwards (action) and in return the road pushes the wheel and the car forwards (reaction).

A race car accelerating is an example of forces in action.

Practise

Practise

There are lots of ways to try out your science skills.

Activity

These interactive online activities from The University of Colorado will help you visualise Newton's first and thirds laws of motion.

Newton's laws of motion
GCSE Physics
BBC Teach - GCSE Physics
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