1. The problem statement, all variables and given/known data A system has a period of 3 seconds. The 4 kg mass oscillates with an amplitude of 0.7 meters. At what position is 50% of its energy in the form of kinetic energy and what is its velocity then? 2. Relevant equations work = Potential energy + Kinetic energy (1/2)kA^2 = (1/2)kx^2 + (1/2)mv^2 3. The attempt at a solution I found k = 17.55 Newton meters. So, I was thinking of two possible approaches: a.) (1/2)kA^2 - (1/2)kx^2 = (1/2)mv^2 b.) kx^2 = mv^2 I'm pretty sure I'd use my second idea. If that's right, what would I plug in for x? The amplitude?