Work done by tension force on a swinging pendulum bob

[Salazar]

"A pendulum bob swings back and forth on a circular path. How much work does the tension force do on the bob?"

That is a question I have. What is the answer symbolically?

 

[Doc Al]

What do you think the answer is and why?

 

[Salazar]

I think it is the product of the tension force, T, and the displacement of the direction it is going, d. T*d, but I am not certain for when it goes in reverse (or forwards). So would it be zero?

 

[Doc Al]

Which way does the tension act? Which way does the pendulum move? (What's the angle between the force and the displacement?)