1. The problem statement, all variables and given/known data In a physics lab experiment, a compressed spring launches a 31g metal ball at a 25 degree angle. Compressing the spring 19cm causes the ball to hit the floor 2.0m below the point at which it leaves the spring after traveling 5.2m horizontally. What is the spring constant? 2. Relevant equations EPE=1/2*k*x^2 KE=1/2*m*v^2 PE=m*g*h Kinematics? 3. The attempt at a solution I know that the initial energy of the system is EPE+PE, and the only unknown is k, the spring constant, but I'm not sure where to go from there. I figured I could find the KE when it hits the ground and use the law of conservation of energy to equate this to my initial energy and solve for k but all attempts at finding that velocity failed.