8. A mass weighing 8 pounds stretches a spring 2 feet. Assuming that a damping force is numerically equal to 2 times the instantaneous velocity acts on the system, determine the equation of motion if the mass is initially released from equilibrium position with an upward velocity of 3 feet per second.

8. A mass weighing 8 pounds stretches a spring 2 feet. Assuming that a damping force is numerically equal to 2 times the instantaneous velocity acts on the system, determine the equation of motion if the mass is initially released from equilibrium position with an upward velocity of 3 feet per second.