(a) If R = 12 cm, M = 360 g, and m = 20 g (below), find the speed of the block after it has descended 50 cm starting from rest. Solve the problem using energy conservation principles. (Treat the pulley as a uniform disk.)
KEi + PEi = KEf + PEf
The Attempt at a Solution
0 + mgh = (1/2)mv^2 + (1/2)Iw^2 + 0
mgh = (1/2)mv^2 + [(1/2)(1/2)mr^2](v/r)^2
mgh = (1/2)mv^2 + [(1/4)mr^2](v/r)^2
4mgh = 2mv^2 + mr^2(v/r)^2
but I don't this has got to be wrong somewhere because the r's will cancel out and I know that they need to be in the equation for velocity..can anyone help? I would greatly appreciate it!