# Conservation of momentum problem regarding a missing mass of a ship!

1. Mar 5, 2013

### MichaelDunlevy

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

After a malfunction, an astronaut escapes from a doomed spacecraft by using an escape pod that is blown off of the ship. The small explosion sends the pod flying away at 34.9 m/s, while the main ship moves in the opposite direction at the speed of 1.89 cm/s. If the combined mass of the astronaut and pod is 1270 kg, what is the mass of the doomed spacecraft?

2. Relevant equations

Conservation of Momentum:

m1u1+m2u2 (initial) = m1v1+m2v2 (final)

3. The attempt at a solution

I believe that conservation of momentum is the correct principle to use here, but I am unsure how to solve for the spaceship's mass because of the missing initial velocity. Could someone help me out? Thanks!
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Mar 5, 2013

### Bandersnatch

Hi there!

The initial velocity was meant to be 0 for both the ship and the pod.
Those velocities provided are for after the separation, relative to their mutual centre of mass.

3. Mar 5, 2013

### Siune

If the spaceship and pod before the launch had 0 momentum to their mutual centre of mass, the conservation of momentum says:

the pod and spaceship must have right after the launch 0 momentum to their mutual centre of mass. So you have 4 variables ( as intial velocities were both 0 ) after the launch; ( mass and velocity of spaceship and pod ).

4. Mar 5, 2013

### MichaelDunlevy

thank you! i figured that the velocity must have been an unknown constant (which would be ridiculous) or 0. I just wanted verification. Thank you for the fast reply guys!