A mass weighing 16 pounds stretches a spring 8/3 feet. The massis initially released from rest from a point 5 feet below theequilibrium position, and the subsequent motion takes place in amedium that offers a damping force that is numerically equal to 1/2the instantaneous velocity. Find the equation of motion x(t) if themass is driven by an external force equal to f(t) = 20 cos(3t).(Use g = 32 ft/s2 for the acceleration due to gravity.)
