Question

A satellite of mass “m” is in a circular orbit of radius 1.5R around the earth of radius R. How much energy is required to move it to an orbit of radius 2R?

(a) -(G*M*m)/12R

(b) (G*M*m)/12R

(c) -(G*M*m)/4R

(d) (G*M*m)/4R

I got this question during an interview for a job.

My doubt is from Gravitation in division Gravitation of Physics – Class 11

Answer 1

The correct option is (a) -(G*M*m)/12R

For explanation I would say: Total energy at 1.5R (TE) = -[(G*M*m)/3R]

Total energy at 2R (TE’) = -[(G*M*m)/4R]

The difference in energy is the required energy.

Difference = TE’ – TE

 = -[(G*M*m)/4R] – [-[(G*M*m)/3R]]

 = -[(G*M*m)/4R] + (G*M*m)/3R]

 = (G*M*m)/12R.