A planet revolves around the sun under the effect of gravitational force exerted by the sun. Why is the torque on the planet due to the gravitational force zero ?

A planet revolves around the sun under the effect of its gravitational force. The torque acting on the planet due to the gravitational force is zero

The torque on a planet about the centre of sun is

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

The gravitational force exerted by the Sun on the Moon is about twice as great as the gravitational force exerted by the earth on the Moon, but still Moon is not escaping from the gravitational influence of the earth. Mark the option which correctly explains the above system.

For a planet revolving round the sun, when it is nearest to the sun