Solving 6kg Cat on Wagon Mass Problem

[I Like Pi]

Homework Statement

If a 6 kilogram cat walks on a stationary cart 1 m/s straight and then the wagon moves back at a speed of 3 m/s what's the mass of the cart?

Homework Equations

The Attempt at a Solution

I was thinking it would be a momentum problem, so mv of cat = mv of cart

I'm not sure I got this right...

 

[collinsmark]

I was thinking it would be a momentum problem, so mv of cat = mv of cart

Assuming that both the cat and the cart are at rest when the cat is not walking, yes, I agree with you.

 

[collinsmark]

Just for clarity though, Be careful about direction. What I should clarified in my last post is

m_catv_cat + m_cartv_cart = 0,

where the velocities can be positive or negative, depending on the direction.