Question

In order to escape a planet's orbit, an object must

Accepted Answer

The object must have the velocity at which the sum of kinetic and its
gravitational potential energy is equal to zero (escape velocity).
Thus 
mv2/2 - G mM/R = 0, where G - is gravitational constant, M - the mass
of the planet, R - is the orbit of the moving object, m - is the mass
of the object.

v = &radic;(2GM/R)

Question #1381

Expert's answer