A 2 kg block hangs without vibration at the bottom end of a spring with a force constant 400 N/m. The top end of the spring is attached to the ceiling of and elevator car. he car is rising with an upward acceleration of 5 m/s2 when the acceleration suddenly ceases at time t = 0 and the car moves upward with constant speed.
The amplitude of the oscillation is
(a) 7.5 cm
(b) 5 cm
(c) 2.5 cm
(d) 1 cm
