1. A block of mass 0.3 kg is pushed against a spring of force constant 250 N/m and compressed a distance of 0.2 m. Assume no friction. a. How much potential energy is stored in the spring? b. After the spring is released, what will be the speed of the block? 2. A small motor runs a lift that raises a load of construction lumber of weight 800 N to a height of 85 m in 45s Assuming that the load is lifted with constant speed, what is the minimum power the motor must produce? 3. A snowboarder (mass = 10kg) coasts on a smooth, frictionless hill that rises from one level to another. If the snowboarder's initial speed is 6 m/s, the snowboarder just makes it to the upper level and comes to rest. Find the height of the hill. 4. Assume friction to be negligible in the roller coaster shown at right. If the roller coaster cart (mass = 25kg) starts at rest at point A, find: a. The speed at the bottom of hill A. b. The speed at the top of hill B