# physics numerical

Let M1 = 20 kg, M2 = 250 kg, r = 30cm = 0.3 m,

F = 0.25 x 9.8 x 10^-6 N

We know that, F = G.M1.M2/r^2

So, G = (F x r^2)/(M1.M2)

= (0.25 x 9.8 x 10^-6 x 0.3 x 0.3)/(20 x 250)

= 0.0441 x 10^-9

Now, g = GM/R^2

M = (g x R^2)/G

= (9.8 x (6 x 10^6)^2)/(0.0441 x 10^-9)

= 8 x 10^24 kg

Thus, the mass of the earth is 8 x 10^24 kg