Consider a planet moving in an elliptical orbit round the sun. The work done on the planet by the gravitational force of the sun

Explanation

False, only at aphlion and perihelion position `F` is perpendicular to `dS`. So, at these two postions work done by gravitational force is zero. At other points angle between `F`and `dS` is not `90(@)`. So, work done is not zero. But, being a conservation force work done in a close path (or in one full rotation ) is zero.