# Recoil Speed - Zero Gravity

1. Oct 5, 2008

### Spartan Erik

1. The problem statement, all variables and given/known data

Two astronauts are initially floating together with zero speed in a gravity-free region of space. The mass of Major Jones is 90 kg and that of Captain Smith is 70 kg. Major Jones pushes Captain Smith away so that Captain Smith attains a speed of 0.4 m/s. The recoil speed of Major Jones is:

0.1, 0.3, 0.5, 0.7, 0.9 m/s

2. Relevant equations

P = Mv
J = change in P

3. The attempt at a solution

I honestly have no idea.. I've searched through my textbook for any similar examples of this type of elastic collision, but I can't find anything

2. Oct 5, 2008

### Janus

Staff Emeritus
What is the momentum of both astronauts before Jones pushes Smith?

What is the total momentum of Smith and Jones before the push?

What is the momentum of Smith after Jones pushes him?

What is the total momentum of Smith and Jones after the push? (Taking into consideration that momentum is conserved.)