1. The problem statement, all variables and given/known data Currently studying for a physics final on Wednesday 12/12/12 The problem can be found here 2. Relevant equations Not very sure. vfball=(v0(mball-mplank)+2mplankv0,plank)/(mball+mplank) mballv0=(mball+mplank)vf 3. The attempt at a solution I have no idea how to do a. I've tried vfball=(v0(mball-mplank)+2mplankv0,plank)/(mball+mplank) But it just comes to 0. b. I've thought about it and the only possible way to get the answer given that I can think of is this: mballv0=(mball+mplank)vf mv0=2mvf vf=v0/2 Does this involve angular momentum as well? Or inertia? Any help would be gratefully appreciated!