A) a block of mass, m, is pushed up against a spring, compressing it a distance x, and is then released. the spring projects the block along a frictionless horizontal surface, giving the block a speed v. the same spring projects a second block of mass 4m, giving it a speed 3v. what distance was the spring compressed in the second case?
b) initially a body moves in one direction and has kinetic energy k. then it moves in the opposite direction with three times its initial speed. what is the kinetic energy now?