# college physics

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A ball of mass 0.70 kg moving with speed of 1.0 m/s hits a wall and bounces back with the same speed in the opposite direction. What is the change in the ball's kinetic energy?

• physics -

The speed doesn't change. What does that tell you?

If you don't know, review the definition of kinetic energy:

(1/2) M V^2

Even if the velocity changes sign, V^2 does not change sign.

The mass M doesn't change, either.

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