State the source of centripetal force that our earth requires to revolve around the sun. List the factors on which this force depends.

(N/A) $(i)$ The centripetal force required for the earth to revolve around the sun is provided by the gravitational force of attraction between the sun and the earth.
$(ii)$ According to the law of universal gravitation,the magnitude of this force depends on the mass of the sun $(M)$,the mass of the earth $(m)$,and the square of the distance $(r^2)$ between their centers. The formula is $F = G \frac{Mm}{r^2}$,where $G$ is the universal gravitational constant.