1. The problem statement, all variables and given/known data Here's the problem in a JPG, with the image: http://docs.google.com/Doc?id=d277r7r_50c9trfbdr (the 25 points is b/c it's a practice test) 2. Relevant equations 3. The attempt at a solution A)KE=0, PE=0 (defined to be at cylinder's initial position) B)PE=Mg(-h) C)Final KE=.5*M*(2gh)^2 (To get this, I used the v^2=vi^2 + 2aX equation, plugged it in for v^2 in KE=.5mv^2) However, I don't think my equations are right because if my KE was that, there would have to be extra energy put into the system for the yo-yo to rotate at all, thus there would be no rotational kinetic energy, which doesn't seem to jive with the original provlem. Where am I going wrong?