a spherical massof 20kg lying on the earth's surface is attracted by another spherical mass of 250kg with a force equal to the weight of 0.25mg wt.the centers of the two masses are 30cm apart. calculate.the mass oeartf earth.radius of earth 6000km.
We have m1 = 20kg, m2 = 250 kg, r = 0.3m, F = 0.25 mg wt = 0.25 x 10 -6 kg wt.
F = 0.25 x 9.80 x 10 -6 N
We have the formula F = G m1m2/ r2
or G = F r2 / m1m2
G = 0.25 x 9.80 x 10 -6 x 0.30 x 0.30 / 20 x 250
= 0.2205 x 10 -6 / 5 x 103
G = 0.0441 x 10 -9
Now g = GM / R2
g = g x R2 / G
= 9.8 x (6 x 106)2 / 0.0441 x 10 -9
= 8000 x 1021
g = 8 x 1024 kg