Alright I'm having a little trouble on this one... One end of a massless spring is welded to a flat surface; the other end points upward. A mass of 2.0kg is set on top of the spring. The spring is then compressed by hand so that the end of the spring is 42cm lower than the position of the spring with no mass on top. The spring is then seddenly released. What is the maximum kinetic energy of the 2.0kg mass?? I think i use the formula KE=1/2mv^2, if that is true could anyone give me a hint on how to find the velocity please? Thankyou!