GCSE Physics

Newtons Third Law

Edexcel

Introduction

  • Newton’s Third Law of Motion states that, for every action, there is an equal and opposite reaction.
  • It explains the fundamental interactions between objects in the universe and help us to understand how forces work in pairs.
Example:
A visual representation of Newton's Third Law of Motion showing walking and the recoil of a gun. For every action force, there is an equal and opposite reaction.
A visual representation of Newton's Third Law of Motion, showing a rocket launching into space and a person swimming. For every action, there is an equal and opposite reaction.

What is Newton’s Third Law of Motion?

  • It states that, when two objects interact, the forces they exert on each other are Equal and Opposite.
  • Equal refers to the magnitudes of two forces whereas Opposite refers to their direction.
Real-life Examples: Running:
  • Action: Our foot pushes backward against the ground.
  • Reaction: The ground pushes us forward with an equal force, making us move.
A visual representation of Newton's Third Law of Motion, showing runners in a sprint race and a person running hurdles. The action of running and hurdling generates an equal and opposite reaction force.
Bird Flying:
  • Action: A bird’s wings push air downward.
  • Reaction: The air pushes the bird upward, allowing flight.
A visual representation of Newton's Third Law of Motion, showing birds flying in the sky and across the water. The birds push air downwards to generate lift, while the air pushes back with an equal and opposite force.

What are the Balanced Forces and Action-Reaction Pairs?

Balanced Forces
  • These are two or more forces that act on the same object, are equal in size, and opposite in direction, so they cancel each other out.
  • No change in Motion or constant Speed (if already moving).

Examples:

Image of a parked car and a book resting on a table, illustrating balanced forces.
Action-Reaction Pairs:
  • These are two forces that act on the different objects, are equal in size, and direction, so they do not cancel each other out.
  • Cause Motion and Accelerates.

Examples:

examples of the third law of newton

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What is Collison?

  • Collison is an example of a Newtons 3rd law of Motion which states that when two objects collide, both objects exert equal and opposite forces on each other.
  • Newtons 3rd Law Applies to Collisions based on:
    • Force Pairs During Impact
    • Momentum Conservation
    • Different Effects Based on Mass
Examples:
Illustration comparing a hammer hitting a nail and a basketball bouncing.
Click the links below to learn more about Newton’s Laws of Motion:

Frequently Asked Questions

Solution: It means that whenever one object pushes or pulls another, the second object pushes or pulls back with the same force in the opposite direction.
Solution: No. Balanced forces act on the same object. Action reaction forces act on different objects.
Solution: No, because they act on different objects, they do not cancel each other.
Solution: When you jump off a small boat, you push back on the boat and the boat moves backward.
Solution: Yes. According to Newtons 3rd law, forces always come in pairs β€” Action and Reaction.

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