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## Homework Statement

Two rockets are launched from Earth's surface, one at 17 km/s and the other at 22 km/s. How fast is each moving when it crosses the moon's orbit?

## Homework Equations

Kf + Uf= K0 + U0

0.5mvf^2 -GMm/R = 0.5mv0^2 - GMm/R

## The Attempt at a Solution

So I attempted to use the equation above, using the earth's mass and the earth's radius, It didn't work, my speeds came out to be exactly 17 and 22 just like from the start. I'm going to say that the radius of the moon and the mass of the moon comes into play here. Can someone help, with perhaps a better equation?