Question

A spring attached to a mass is at rest in the initial position (not shown). The spring is compressed in position A and is then released, as shown in position B. Which equation describes conservation of energy in position A?

E = one halfmv2
E = mgh
E = one halfkx2
E = one halfk2x2

Answer 1

E = 1/2 k x^2

At position A the mass is momentarily at rest so kinetic energy is zero; the mechanical energy is stored as spring potential energy (1/2 k x^2).