Solve Physics Problem: 3000kg Space Capsule

[bondgirl007]

Homework Statement

A 3000kg space capsule is traveling with a velocity of 200m/s. In an effort to alter its course, it fires a 25.0 kg projecticle perpendicular to its original direction of motion at a speed of 2000 m/s. What is the speed of the capsule and by what angle has its direction changed.

* my teacher said assume mass stays the same*

Homework Equations

P = mv
m1v1 + m2v2 = m1v1' + m2v2'
M = m1 + m2
V = combined velocity

The Attempt at a Solution

MV = m1v1' + m2v2'
(3000)(200) = (3000)(v1') + (25)(2000)
v1' = 1833.3

Is this right so far? I'm very confused and am not sure if I should be using Pythagoras to find it or what?

 

[bondgirl007]

Can anyone please help me out? I've been stuck on this question for over half an hour. :(