A 2kg block hangs without vibrating at the bottom end of a spring with a force constant of 400 N/m. The top end of the spring is attached to the ceiling of an elevator car. The car is rising with an upward acceleration of 5 m/s 2 when the acceleration suddenly ceases at time t = 0 and the car moves upward with constant speed. (g = 10 m/s 2 )
(i) What is the angular frequency of oscillation of the block after the acceleration ceases?
Text Solution
Verified by ExpertsCHECK THE SOLUTION.
(i) Maximum extension the spring from natural position is x.
Then mg + ma = kx
⇒ x =
= 7.5 cm
(ii) Extension of the spring when it is stretched to equilibrium line is x'.
mg =kx'
⇒ x' =
= 5 cm
Therefore amplitude A = x –x' = 2.5 cm
(iii) If upward direction is taken as positive at t = 0, x = – A
Using x = A sin (ꞷt + φ )
– A = A sin φ
φ = 

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