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JEE Main202120 Jul 2021Evening ShiftPhysicsMotion in Two DimensionsActual

A boy reaches the airport and finds that the escalator is not working. He walks up the stationary escalator in time t 1 . If he remains stationary on a moving escalator then the escalator takes him up in time t 2 . The time taken by him to walk up on the moving escalator will be:

Options

  1. At 1 t 2 t 2 - t 1
  2. Bt 1 + t 2 2
  3. Ct 1 t 2 t 2 + t 1
  4. Dt 2 - t 1

Correct answer

C. t 1 t 2 t 2 + t 1

Step-by-step solution

L = Length of escalator V b / ecc = L t 1 When only escalator is moving, V esc = L t 2 when both are moving, V b / g = V b / esc + V esc V b / g = L t 1 + L t 2 ⇒ t = L V b / g = t 1 t 2 t 1 + t 2

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