Gravitation Part 1

Gravitational potential energy E=−‌

GMm

r

where M= mass of earth
m= mass of body
r= radius of earth
Energy required to move a body of mass m from an orbit of radius 2R to 3R
=( Potential energy of the Earth-mass system when mass is at distance 3R)− (Potential energy of the Earth-mass system when mass is at distance 2R )
=‌

−GMm

3R

−(‌

−GMm

2R

)
=‌

−GMm

3R

+‌

GMm

2R

=‌

−2GMm+3GMm

6R

=‌

GMm

6R