1. The problem statement, all variables and given/known data Two elastic balls of mass m1 = 0.3kg and m2 = 0.2kg are hanging on a thin rope so that their centre of gravity is on the same height. ball 1 goes out of balance raising it up to h0 = 0.05m Then letting it go hitting ball 2. Calculate the maximum height of both balls reaching after the collision. m1 = 0.3kg m2 = 0.2kg h0 = 0.05m g = 10m/s2 and since m2 is not moving it's V2 = 0m/s h1 = ? h2 = ? 2. Relevant equations I'm not 100% sure, but I do know I am supposed to use the elastic collision equation: m1*V1+m2*V2 = m1*V1'+m2*V2' since V2 = 0m/s it's: m1*V1 = m1*V1'+m2*V2' And I'm guessing kinetic energy: ΔEk = 4 * m1*m2/(m1+m2)2 * Ek1 Ek1 = 1/2*m1*V12 3. The attempt at a solution First I made a drawing of it to understand it better. A 2 ball Newton cradle. I just don't see how am I supposed to collide those 2 equations and then the height. And what am i supposed to do with g = 10m/s2 ??