1. The problem statement, all variables and given/known data N bricks, each having height h and mass m, are lying on the floor in a configuration of minimal potential energy. What is the minimum energy required to put all bricks one on top of another? 2. Relevant equations U=mgy 3. The attempt at a solution As (I assume) they are all flat on the floor with minimum potential energy, I think this problem is mainly about the most efficient way to stack the bricks. Is the energy used to stack the bricks the same as the difference in potential energy from the starting position (presumably 0 J) and the ending position (mgNh)? And how does that translate into a MINIMUM ENERGY requirement?