Amass of 50 g stretches a spring 3.828125 cm. if the mass is set in motion from its equilibrium position with a downward velocity of 30 cm/s, and if there is no damping, determine the position u of the mass at any time t. assume g = 9.8 m/s^2. enter the exact answer. u(t) = 3/16 sin (160 t) when does the mass first return to its equilibrium position? enter the exact answer. use "pi" or symbol pi to enter the pi, if needed.