1. The problem statement, all variables and given/known data This is the answer : For part d) of this question, I don't understand "stretching/extension reduces and velocity increases/height increases" . 2. Relevant equations Hooke's Law: F=kx 3. The attempt at a solution Ok, so if extension is reduce, then force reduces too. Then how does a decrease in force causes the velocity and height to increase? Does it have something to do with the principle of conservation of energy, where a gain in kinetic energy equals to a lose in gravitational potential energy?