Energy in Simple Harmonic Motion help?

Question

A .150 kg mass is attached to a spring with k=18.9 N/m. At the equilibrium position, it moves 2.39 m/s. How mych mechanical energy does it have?

Answer 1

At the equilibrium position, the spring is not stretched or compressed, and therefore has no potential energy.  Then the total energy of the spring/mass system is the kinetic energy of the mass at the equilibrium position.  Calculate the kinetic energy at equilibrium, and that will be your answer.

 

E = (1/2)mv² = (1/2)(0.150 kg)(2.39 m/s)² ≅ 0.428 J