A body of mass m kg starts falling from a distance 2R above the earth's surface. What is its kinetic energy when it has fallen to a distance 'R' above the earth's surface ? (where R is the radius of Earth)

Explanation

By conservation of mechanical energy.
`("GMm")/(3R)+0=("GMm")/(2R)+"K.EE."`
`implies"K.E."=("GMm")/("R")[(1)/(2)-(1)/(3)]`
`=(1)/(6)("GMm")/("R")=(1)/(6)((gR^(2))m)/("R")=(1)/(6)" mgR."`