Momentum and Impulse of a bullet

[AnomalyCoder]

Homework Statement

This is a two part question.
Kim holds a 2.0kg air rifle loosely and fires a bullet of mass 1.0g. The muzzle velocity of the bullet is 150m/s. What is the recoil speed of the rifle?
^ I got -.075m/s

Part Two:
If Kim in the previous questions holds the rifle tightly against her body, the recoil speed is less. Explain. Calculate the new recoil speed assuming the girl has a mass of 48kg.

Homework Equations

p = mv
Impulse = Change In Momentum
To Solve the first problem, I used: 2kg*0m/s + .001kg*0m/s = 2k*x(m/s)+.001kg*150m/s
(I

The Attempt at a Solution

I'm not really sure how to use this new information given. That is, how do I apply it to the equation I used before? I just need someone to give me a hint, or a concept, and I should be able to figure it out...

 

[cepheid]

I'm pretty sure you're just supposed to consider Kim + the rifle to be a single rigid body so that the bullet has to make their combined mass recoil rather than just the rifle.

 

[AnomalyCoder]

That makes sense. I understand how to solve it, I just wasn't sure what to consider the body to do with the problem. Thanks for the advice! So pretty much, one would combine 2kg and 48kg together. Therefore:
50kg*0 + .001*0 = 50kg(x)+.001(150m/s)
0 = 50x+.15
-50x = .15
Ergo
x = -.003