# Escape velocity of an Earth-Moon system

1. Sep 16, 2014

### cragar

1. The problem statement, all variables and given/known data
What velocity is required to escape from the Earth-Moon system from the surface of
the Moon? Assume that all of the necessary velocity is imparted at once, as with a
cannon or rail gun on the Moon itself. In what direction must the initial velocity vector
be pointed to ensure the lowest escape velocity?
3. The attempt at a solution
Would i just find the center of mass between earth and the moon and then use the distance from the center of mass to the surface of the moon to find the escape velocity.

2. Sep 16, 2014

### BvU

What you need is some relevant equations. Any suggestions ?
Suppose you have this center of mass position. Then what ?

3. Sep 16, 2014

### tjmiller88

Ask yourself: what is escape velocity?

What are you "escaping" from and how might it be relevant to the Earth and Moon?

Your starting point, once you've answered those questions, should be a diagram of the Earth and Moon, showing some relevant forces.

4. Sep 16, 2014

### Staff: Mentor

...and velocities; The Earth and Moon are not stationary with respect to one another