1. The problem statement, all variables and given/known data In a physics lab a cube slides down a frictionless incline and elastically strikes another cube at the bottom that is only half it's mass. If the incline is 30 cm high and the table is 90 cm off the floor where does each cube land? 2. Relevant equations mgh=1/2mv^2 v=at+v_o x=.5at^2 +v_o*t +x_0 conservation of momentum/energy 3. The attempt at a solution I know that this problem has three parts, conservation of energy, collision and projectile but I had a question about the mass. so I simply use 2m and M or can i substitute any value in as long as it;s twice the value of the smaller block? I know how to solve all parts but this first part stumbled me a little bit. Thanks in advance, all help is appreciated!