posted by Stacy .
An ore car of mass 42000 kg starts from rest and rolls downhill on tracks from a mine. At the end of the tracks, 6.8 m lower vertically, is a horizontally situated spring with constant 3.8 x 10^5 N/m. The acceleration of gravity is 9.8 m/s^2.
How much is the spring compressed in stoping the ore car?