1. The problem statement, all variables and given/known data You have a pendulum with a ball of mass m at the end, and the pendulum is held parallel to the ground. This pendulum is also a spring, however, with spring constant k and equilibrium length L. You let go of the weight. What is L', the new length of the spring at the bottom of the swing, and what is the velocity of the ball? 2. Relevant equations Conservation of mechanical energy E=(1/2)m*v^2 + m*g*h + (1/2)k*x^2 (where k is the spring constant) Integral of force with respect to time = change in momentum Work equations other conservation laws that I may not be thinking of 3. The attempt at a solution I've tried creating equations for the force and integrating it, but if I do it in terms of the angle of the pendulum, I have to make that a function of time and I haven't been able to figure out how much time it would take to reach the bottom of the swing. I've also tried conservation of mechanical energy, but I end up not knowing both the KE or the spring force so I can't get anywhere. I haven't taken a math class in two years, but I've had linear algebra, multi-variable calc, and differential equations so you can explain the solution in terms of those if you like. I guess I'm just a bit rusty because I can't get this one.