Question:
Different points in the earth are at slightly different distances from the sun and hence experience different forces due to gravitation. For a rigid body, we know
that if various forces act at various points in it, the resultant motion is as if a net force acts on the cm causing translation and a net torque at the cm causing
translation and a net torque at the cm causing rotation around an axis through the cm. For the earth-sun system
(a) the torque is zero
(b) the torque causes the earth to spin
(c) the rigid body result is not applicable since the earth is not even approximately a rigid body
(d) the torque causes the earth to move around the sun
Solution:
The correct answer is (a) the torque is zero