Since they are both of the same mass while at the top of the hill both rocks would have 0 kinetic energy and 100 potential energy. Once the first rock starts to roll down the hill once it is at the middle of rolling down the hill then it will have 50 kinetic energy and 50 potential energy. Then when the second rock rolls down then it will have 50/50 and once the first rock hits the bottom it will have 100 kinetic energy and 0 potential energy. So the first rock will reach the bottom first therefore it will have the most kinetic energy sooner.
