# physics

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A 20g plastic ball is moving to the left at 30 m/s. How much work must be done th cause the ball to move to the right at 30 m/s?

• physics -

Work must be done to stop the ball, which would be equal to the kinetic energy of the ball, or
W1=(1/2)mv²
=(1/2)*0.02*30²
=9 J.
The same work is needed to give the ball the same kinetic energy as before, but in the opposit direction, so
W2=9 J.

The total work required is W1+W2.

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