Everyday Physics

Why does a ball bounce off the ground?

Have you ever wondered why a ball bounces back when you drop it on the ground?

Newton’s Third Law of Motion gives us the answer:

Every action has an equal and opposite reaction.

When the ball is released by you, it is pulled by gravity and starts going faster and faster.When it reaches the ground, it is at its fastest speed. Because of this speed,the ball pushes on the ground when it hits it. Applying the Newton’s Third Law, the ground pushes back on the ball with an equal force to first stop the ball and then push it back into the air.

Now you may ask why the ball does not come back up to the height it was dropped from.

This is because the ball is first stopped by the ground and then pushed back up, so although the force is the same, the ground is only able to push the ball with a speed less than when it hit the ground.

What is gravity?

Gravity is a force that any object with mass exerts on any other object with mass. It is a force which causes objects to pull each other. This force makes things fall to the ground and also keeps us on the ground.

As an analogy, imagine tying a rope to an object and pulling on it. The object is attracted towards you. Gravity is the imaginary ‘rope’ which pulls object that have mass towards other objects that have mass.

When a ball falls to the group because of this ‘rope’, it keeps on moving till it reaches the ground, at which point it is stopped by the ground, which means that this ‘rope’ ends. Then the ground pushes it back, making it bounce back up.


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