Q: A force $ \vec{F}= \frac{-ky}{\sqrt{x^2 + y^2 }} i + \frac{k x}{\sqrt{x^2 + y^2 }}j $ N is applied on a block, whose position is P (x , y). The block moves on a circular path of radius R. find the work done by the force F in complete rotation.
(a) 2 π Rk
(b) π Rk
(c) 4π Rk
(d) Zero
Ans: (a)