6. A 0.25kg block is dropped onto a spring that is at its equilibrium position. The spring has a spring constant of 250N/m. The block compresses the spring 0.12m before it momentarily stops. When the spring is compressed : a) what is the work done on the block by the gravitational force? b) what is the work done on the block by the spring force? c) what is the speed of the block just before it hits the spring? d) If the speed is doubled at impact, how much does the spring compress