65 the length of a spring increases by 7.2 cm from its relaxed length when a mass of 1.4 kg is hanging in equilibrium from the spring. (a) what is the spring constant? (b) how much elastic potential energy is stored in the spring? (c) a different mass is suspended, and the spring length increases by 12.2 cm from its relaxed length to its new equilibrium position. what is the second mass?
