# Why does a ball bounce?

If an object is acted on by equal and opposite forces then it will be in equilibrium, and it's acceleration or velocity (and so direction as well) will not be changed.

So when a ball bounces, it exerts a force on the floor, which matches the magnitude of the force in the opposite direction (the ball is bouncing perfectly vertical), up. So how is it's velocity/direction changed? If the forces are equal and opposite to each other. In order for it bounce, surely the force acting from the floor to the ball must be greater than the force acting from the ball to the floor?

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You've misunderstood the statement.

When A exerts $\vec{F}_{A \to B}$ on B, B exerts an equal and opposite force $\vec{F}_{B \to A} = - \vec{F}_{A \to B}$ on A.

The only forces acting on the ball a gravity and the normal force, and the floor experiences a force from the ball which is equal in magnitude and opposite in direction from the normal force on the ball.

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I don't understand you're last paragraph. If the forces are equal and opposite why is there a change in motion? –  Jonathan. May 24 '12 at 20:06
One of the equal and opposite forces acts on the ball, and the other one acts on the floor. When you add up the forces acting on ball it includes only one of the pair. –  dmckee May 24 '12 at 20:08
That seems so obvious now you've said it :) –  Jonathan. May 24 '12 at 20:13