Ok. I need help in how to even just start this problem. "Starting with an initial speed of 5.00 m/s at a height of 0.280 m, the 1.75 kg ball swings downward and strikes the 4.75 kg ball that is at rest. a) Using the principle of conservation of mechanical energy, find the speed of the 1.75 kg ball just before impact. b) Assuming that the collision is elastic, find the velocities (magnitude and direction) of both balls just after the collision. c) How high does each ball swing after the collision, ignoring air resistance?" I know that the formula I will be using is: 0.5mvf^2 + mghf = 0.5mvo^2 + mgho But I'm confused which m's will be for the first ball and second ball. I tried to do this: 0.5m1vf1^2 + m2ghf = 0.5m1vo1^2 + m2gho but then i feel like that doesn't make sense. Why is ho & hf only multiplied by m2 and not m1.... I don't know. And for question a) how do you find the answer right before impact? I know how to find it after impact, and before impact, but how do you find it right before impact? I need help... thanks!