A 2.4kg block is dropped onto a spring with a force constant of 3.96*10^3 N/m from a height of 5m. When the block is momentarily at rest, the spring is compressed by 25cm. Find the speed of the block when the compression of the spring is 15cm. Relevant equations: External Work = change in mechanical energy = change in potential energy of spring + change in potential energy of gravity + change in kinetic energy External Work = 0 for change in potential energy of the spring I did final - initial 1/2 K (.15m)^2 - 1/2 K (.25m)^2 = -79.2J for change in potential energy of gravity I did final - initial ?? - mgh for change in KE I did final - initial 1/2 m v^2 - 0 Im not sure what the final potential energy of gravity is... should it be 0 since it is converted to potential energy of the spring? Would it be 0 = -79.92 - mgh + 1/2 m v^2 and solve for v?