A block of mass 0.39 kg connected to a spring with spring constant 30 N/m is oscillating on a frictionless horizontal surface. Its speed as it passes through its equilibrium position is 0.5 m/s. What is the total energy of the system in J?

Answer 1

at the equilibrium position, there is no energy stored in the spring, it's all in the kinetic energy of the block

KE = 1/2 m v²