1. A pendulum bob of mass m is released from a height H above the lowest point. It collides at the lowest point with another pendulum of the same length but with a bob of mass 2m initially at rest. Find the heights to which the bobs rise given that the collision is (A) Completely Inelastic, (B) Perfectly Elastic. 2. Relevant equations (conservation of linear momentum) m1u1 + m2u2 = m1v1 + m2v2 (conservation of energy) .5mv^2 + mgh = .5mv^2 + mgh 3. The attempt at a solution initial PE = mgH = final KE at lowest point = 0.5 mu^2 (A) Completely Inelastic total mass = 3m final PE = 3m g *h mgH = 3mg h h = H/3 ***answer is supposed to be H/9??*** (B) Perfectly Elastic mgH= 0.5 mu^2 0.5 *m *u^2 + 0.5 * 2m *0^2 =0.5 * m * 0^2 + 0.5 * 2m * v^2 0.5 *m *u^2 = 0.5 * 2m * v^2 0.5 * 2m * v^2 = mgH KE of 2m at lowest point = PE at height point 0.5 * 2m * v^2 = 2m g h1 mgH = 2mg h1 h1 = H/2 ***answer is supposed to be H/9, and 4H/9??*** Could anyone help me as to why I've got the wrong answers?