1. The problem statement, all variables and given/known data (apologies for the bad picture, but it was the only one I could find online) 2. Relevant equations Conservation of energy, KE1 + PE1 = KE2 + PE2 PE = mgh KE = 0.5mv² 3. The attempt at a solution I'm not sure where to begin. I know the answer but I don't know how you get it. Can't you simply use conservation of energy here? At the top PE = mgr and KE = 0... and at the bottom PE = 0 and KE = 0.5mv². If I do that v = √2gr, but the answer is actually √(gr(π/2 + 4/π)). I'm not sure what to do with the mass per unit length (density?) either and how it's relevant to this equation. Steps on how to solve this problem would be appreciated.