A 650 g bird is stuck on the upper free end of a vertical spring with a spring constant of 14 N/m. The bottom of the ideal spring is tied to the earth. The bird trying to liberate itself from the spring flies vertically at a time t = 0 s, producing a constant vertical force of 12 N. The spring has been stretched 64 cm at time t. Determine the speed of the bird at time t.