An object dropped in a stationary lift takes time t 1 to reach the floor. It takes time t 2 when lift is…

An object dropped in a stationary lift takes time t1 to reach the floor. It takes time t2 when lift is moving up with constant acceleration. Then
  1. t2>t1
  2. t1>t2
  3. t1t2
  4. t1=t2

Solution

When the object is dropped in a stationary lift from height h,

s=ut+12at2-h=0t1+12-gt12t1=2hg

When the object is dropped from a lift which is moving up with an acceleration a, then a pseudo force will act on the object since the object is in a non-inertial frame of reference, therefore net acceleration due to gravity and pseudo force on the object will be, -g+a in the downward direction.

s=ut+12at2-h=0t+12-g+at22t2=2hg+a

Thus, it is clear that t1>t2

Asked in: AP EAMCET 2021 (19 Aug Shift 1)

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