A rocket of mass,m is located at an alttitude h meters above the surface of a planet of a mass,M and radius, R.

*write an expression for the gravitational pull on it.
*Deduce an expression for the gravitational potential and escape velocity at that location.

1 answer

F = G m M/r^2 = G m M/(R+h)^2
potential = - G m M /(R+h)
(1/2) m v^2 = G m M/(R+h)
so
v^2 = 2 G M/(R+h)