Abumper cart has a mass of 200 kg and has a protective bumper around it that behaves like a spring. the spring constant is 5000 n/m. if the cart is moving at a speed of 8 m/s towards a solid barrier, and upon impact, is momentarily brought to rest. a) how much elastic potential energy will be stored in the spring when it is fully compressed? b) what is the average force exerted by the spring if it is compressed by a distance of 0.2 meters?