# Homework Help: Zero-momentum frame - total momentum in this frame

1. Apr 10, 2014

### Cantique

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

Assume that all particles are non-relativistic, that the target X is initially at rest,
and that x has kinetic energy Tx in the laboratory frame. Show that the total kinetic
energy of the reactants in the centre-of-mass frame is given by T* = μTx/mx, where mx is
the mass of particle x and μ the reduced mass of x and X. Also obtain an expression for
p* in terms of T* and μ.

2. Relevant equations

I have completed the first part of this question without a problem. The second part, requiring p* to be found doesn't make sense to me. Surely the total momentum in the zero-momentum frame should be zero? Or is it expecting a different quantity?

3. The attempt at a solution

First part done. Second part - don't know what it is asking.

2. Apr 10, 2014

### dauto

I agree. The problem isn't clear. One possible interpretation is that p* is the momentum of the incoming particle - as opposed to total momentum - as seen in the center of mass ref. frame.