Posted by **nathan** on Tuesday, November 23, 2010 at 2:26pm.

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 -
**MathMate**, Tuesday, November 23, 2010 at 4:29pm
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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