Here is the problem:
"Two blocks of masses 1m and 3m are placed on a frictionless surface. A light spring is attached to the massive block, and the blocks are pushed together with the spring between them. A string holding the 2 blocks together is cutt, sending the 3m black to the right with speed of 2 m/s.
Find the systems original elastic potential Energy, taking m = .350kg ?"
I cant seem to find out what forumla to use to get the original elastic potential energy... ?