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## Homework Statement

Compute the escape velocity for a projectile fired from the surface of the moon.

The moon’s radius is 1700 km, and its surface gravity is ##1.62 m s^(−2)## . Neglect the effect

of the Earth. A second projectile is fired horizontally from the lunar surface with a velocity f times the escape velocity. Find the minimum value of f for the projectile to

go into orbit.

## Homework Equations

## The Attempt at a Solution

So I have done the first part by simply equating the energy to zero ##1/2*m*v^2 = GMm/R## and noting that ##g=GM/R## its easy to show that ##v=sqrt(2*g*R)##

However, I am confused about the second part since I have not been given a radius of orbit. So my first thought was that the minimum energy of an orbit is a circular orbit, so am I supposed to find the energy required to put the projectile into an orbit of radius R? ##1/2*m*(fv)^2=GMm/R## ?

Many thanks :)