1. The problem statement, all variables and given/known data Three objects of equal mass, A, B and C, are released from rest at the same instant from the same height on identical ramps. Objects A and B are both blocks, and they slide down their respective ramps without rotating. Object C rolls down the ramp without slipping. Its moment of inertia is unknown. Objects A, B and C are made of different materials, thus the coefficients of friction between the objects and their corresponding ramps are not necessarily the same. Object A reaches the bottom of its ramp first, followed by objects B and C, which reach the bottom at the same instant. Rank the center of mass accelerations, the net forces and the frictional forces exerted on objects A-C according to magnitude, from largest to smallest. 2. Relevant equations conceptual 3. The attempt at a solution Because B and C arrive at the bottom at the same time, then its center of mass accelerations are the same, and ranking the center of mass accelerations from largest to smallest, it would be A>B=C, right? The net forces would be the same for B and C because the accelerations are the same, and greater for A, as the acceleration is greater. But what about frictional force? Wouldn't we need to know the coefficients of friction for the ramps to know this?