A 20 kg box is attached to a compressed spring that has a spring constant of 300 N/m. The box is resting on a frictionless surface and the spring is compressed 30 cm. What is the EPE of the spring? What will be the KE of the box when the spring expands back to its natural length? How fast will the box be moving after the spring releases the box? 1.16m/s If it were fired straight up, what would its final gravitational potential energy be? How high would it go?