Does Tension Do Any Work in Uniform Circular Motion?

[Heat]

Homework Statement

A ball of mass 0.765 kg is tied to the end of a string of length 1.59 m and swung in a vertical circle.

During one complete circle, starting anywhere, calculate the total work done on the ball by the tension in the string.

During one complete circle, starting anywhere, calculate the total work done on the ball by gravity.

Repeat part (a) for motion along the semicircle from the lowest to the highest point on the path.

Repeat part (b) for motion along the semicircle from the lowest to the highest point on the path.

Take all free fall acceleration to be 9.8 m/s^s

Homework Equations

W = F * s
K = .5mv^2

The Attempt at a Solution

For the first part,

I tried getting the C, by using C = 2pi1.59^2
c = 9.99
then 9.8(9.9) = 97.02, but it's incorrect :(

 

[learningphysics]

What is the definition of work? Hint... the tension at any time is perpendicular to the displacement at that particular time...