The Earth and the moon experience equal gravitational forces from each other. However, the mass of the Earth is much larger than the mass of the moon. Hence, it accelerates at a rate lesser than the acceleration rate of the moon towards the Earth. For this reason, the Earth does not move towards the moon.
A small point of mass is placed at a distance from the center of a big uniform solid sphere of mass and radius . The gravitational force on due to is . A spherical part of radius is removed from the big sphere as shown in the figure, and the gravitational force on due to the remaining part of is found to be . The value of the ratio is: