# Physics

A 1.0-kg ball on the end of a string is whirled at a constant speed of 2.0 m/s in a horizontal circle of radius 1.5 m. What is the work done by the centripetal force during one revolution?

I did:
F=m(v^2)/r
F=1(2^2)/1.5=2.7 J

The answer that was provided was 0. Can someone explain the reasoning? Thanks

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1. It seems to me that centripetal force is directed inward, but the direction of travel is tangent to the circle. How can a force ninety degrees to travel do any work?

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bobpursley
2. There is no displacement in the direction of the force.
work=force * displacement in the direction of the force.

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3. The object has no displacement during that time, therefore no work is done. Plus the ball traveled at a constant speed which makes the accleration zero, the force zero, and the work zero.

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4. Work is transferred, not made.

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5. If you look at the final displacement after a full revolution, it will be back where it started. Since work is Force dot Displacement, since displacement is zero, so is work.

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