Preeti reached the metro station and found that the escalator is not working. She walked up the stationary escalator in time t₁. On other days, if she remains stationary on the moving escalator, the escalator takes her up in time t₂. The time taken by her to walk up on the moving escalator will be:
Options

Question

Preeti reached the metro station and found that the escalator is not working. She walked up the stationary escalator in time t₁. On other days, if she remains stationary on the moving escalator, the escalator takes her up in time t₂. The time taken by her to walk up on the moving escalator will be:

Options

G1 Physics · Accepted Answer

Step 1: Let escalator length be d. Her walking speed relative to escalator is d/t₁ and escalator speed is d/t₂. Step 2: While she walks on the moving escalator, ground speed is d/t₁+d/t₂. Step 3: Time = d/[d/t₁+d/t₂] = t₁t₂/(t₁+t₂). Final answer: C.