1. The problem statement, all variables and given/known data We did an experiment in class where a marble was released down a ramp and traveled a short distance before entering a hole inside an upside down cup, causing the cup to get displaced. Different masses were placed on top of the cup and the resulting displacements were measured. We have to discuss the physics behind the experiment. We graphed distance against mass on top of the cup. 2. Relevant equations 1. Friction force = u N 2. Work Done = force x distance 3. The attempt at a solution The marble has GPE equal to height of ramp x 9.81 x mass of marble. As it rolls down the ramp and strikes the back of the cup, this energy results in work being done on the cup which is equal to GPE minus any frictional losses on the way. The bigger the mass on the cup the bigger the static frictional force according to the above equation. I'm struggling to explain in rigid physics sense why the cup moves a smaller distance with more mass on it. The energy available to be transferred into work done is fixed (i.e. total GPE) so what determines how much is transferred into work done? Will the force in equation 2 be the same each time?