1. The problem statement, all variables and given/known data Three 10 kg blocks are stacked on top of each other on top of a frictionless table. A hand touching the bottom block applies a force of 90 N to the right. The coefficient of friction between the blocks is sufficient to keep the blocks from moving with respect to each other. What is the total force exerted on the middle block by the bottom block? 2. Relevant equations Fn=Fg=mg Fs≤usFn 3. The attempt at a solution I drew a diagram and have determined that the forces acting on the middle block are the normal and frictional forces from both the top and bottom block. But since it's only asking for the bottom block, I think I can what the top block is doing. I know that the normal force must be 98 N (10 kg x 9.8 m/s2) but I can't figure out what the frictional force would be. I know it must be greater than 90 N if it's resisting the push of the hand, but I don't know how I would find the "upward" force it is is giving to the block above.