Page 60 - Force 10

(ii) Density of earth ( ):

Let be the average density of the earth. Suppose earth is a sphere of radius R.

∴ Mass = volume x density

M = x

Or, = x

Or, = ……..(ii)

We know, g = 9.8m/ 2

6
Radius of earth (R) = 6.37 x 10 m
2
Gravitational Constant (G) = 6.67 x 10 −11 N −2

Thus, equation (ii) gives

3
= 5.5 x 10 kg/ 3

This is the average density of the entire earth.