A stone of mass m is tied to a light, inextensible string and whirled in a horizontal circle of radius r with uniform speed.
a. (i) Define physical work done by a force.
b. (ii) Explain, without using any numerical calculation, why the tension in the string does no work on the stone during one complete revolution.
c. (iii) Would your answer in part (ii) change if the speed of the stone gradually increases while it is being whirled in the same circle? Give reasons for your answer.