1. The problem statement, all variables and given/known data Two 100g blocks are held 80 cm above a table. As shown in the figure, one of them is just touching a 80cm-long spring. The two blocks are released at the same time. The block on the left just hits the table at exactly the same instant as the block on the right first comes to an instantaneous rest. 2. Relevant equations Conservation of energy! mgh = 0.5kx^2 3. The attempt at a solution So for the spring system, we know that net Fy = 0, therefore -kx = mg therefore x = mg/-k. I plugged that x value back into the "0.5kx^2" side to eliminate the x variable and just have a single isolated k. From there on I was able to isolate appropriately to find a potential value for k. Is my logic correct? It seems a bit bizarre that we don't deal with the other non-spring system.