Write down the average value of g on the earth's surface.

The average value of g on the surface of the earth is 9.8 m s 2 . As we know, Taking the mass of earth M = 5.96 x 10 24 kg and the radius of earth R = 6.37 x 10 6 m, G = 6.67 x 10 -11 N m 2 kg -2 , the force of gravity on a body of mass m = 1 kg on the surface of earth will be F = = 9.8 N. Thus, earth attracts a body of mass 1 kg by a force of 9.8 N towards it's centre.