Physics
posted by Marisol .
A 1.0kg 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

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?

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

Work is transferred, not made.