At what times does the mass pass through the equilibrium position? A mass weighing 4 N is attached to a spring whose spring constant is 16 N/m. What is the period of simple harmonic 6. A force of 400 N stretches a spring 2 m. A mass of 50 kg is attached to the end of the spring and is initially released from the equilibrium position with an upward velocity of 10 m/s. Find the equation of motion. motion?