1. The problem statement, all variables and given/known data A massless spring of length 0.260 m is in its relaxed position. It is compressed to 68.0 percent of its relaxed length, and a mass M=0.240 kg is placed on top and released from rest (shown on the right). The mass then travels vertically, taking 1.60 s to reach the top of its trajectory. Calculate the spring constant. 2. Relevant equations F = -kx Spring potential = 0.5kx^2 3. The attempt at a solution I would prefer if someone explained the concept behind it so that I can work it out myself, rather than people just posting answers.