 Calculate the average density of the Earth.
 Derive how does the value of gravitational force F between two objects change when
 distance between them is reduced to half and
 mass of an object is increased four times.
 Suppose, the radius of Earth is R, then its volume will be

 Let gravitational force be F when the distance between them is R,
…(1)
Now, when the distance reduces to half,
…(2)
On dividing Eq. (1) by Eq. (2), we get
 When the mass becomes 4 times,
 Let gravitational force be F when the distance between them is R,