Preeti reached the metro station and found that the escalator was not working. She walked up the stationary escalator in time t1. On another day, if she remains stationary on the moving escalator, then the escalator takes her up in time t2. The time taken by her to walk up on the moving escalator will be
- t1t2t2-t1
- t1t2t2+t1
- t1-t2
- t1+t22
Answer
(2) t1t2t2+t1
Solution
Let the length of the escalator be L.
Speed of Preeti relative to the escalator, v1 = Lt1; speed of the escalator, v2 = Lt2
Walking up the moving escalator, speed relative to ground = v1 + v2
t = Lv1 + v2 = L Lt1 + Lt2
t = t1t2t1 + t2
Answer: (2)