1. The problem statement, all variables and given/known data A block released from height h hits a spring with constant k, the box compresses the spring a distance x then returns to the same height. Find the maximum speed of the block. 2. Relevant equations K=1/2mv2 U=mgh 3. The attempt at a solution This solution was provided by my professor but I have a couple of questions about it. The equilibrium point is Sequ =mg/k so this is where potential energy is it's lowest and kinetic energy is at it's highest. 1/2mvmax2=mg(h+Sequ) - 1/2k(Sequ)2 mg(h+mg/k) - 1/2k (mg/k)2 1/2 mvmax2 = mgh + 1/2 (mg/k)2/k vmax2 = 2gh + (m/k)g2 vmax = √(2gh + (m/k)g2) I am confused as to why my professor set Sequ equal to mg/k. Did this come from Fspring = kx? Could someone explain this to me?