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JEE Main & Advanced Physics Two Dimensional Motion JEE PYQ - Two Dimensional Relative Motion

  • question_answer
    A person climbs up a stalled escalator in 60 s. If standing on the same but escalator running with constant velocity he takes 40 s. How much time is taken by the person to walk up the moving escalator? [JEE ONLINE 12-04-2014]

    A) 37 s

    B) 27 s

    C) 24 s

    D) 45 s

    Correct Answer: C

    Solution :

    [c] Person’s speed walking only is 1 "escalator" \[\frac{1}{60}\frac{\text{ }\!\!'\!\!\text{  }\!\!'\!\!\text{ escalator }\!\!'\!\!\text{  }\!\!'\!\!\text{ }}{\text{second}}\]
    Standing the escalator without walking the speed is \[\frac{1}{40}\frac{\text{ }\!\!'\!\!\text{  }\!\!'\!\!\text{ escalator }\!\!'\!\!\text{  }\!\!'\!\!\text{ }}{\text{second}}\]
    Walking with the escalator going, the speed add.
    So, the person’s speed is \[\frac{1}{60}+\frac{1}{40}=\frac{15}{120}\]\[\frac{\text{ }\!\!'\!\!\text{  }\!\!'\!\!\text{ escalator }\!\!'\!\!\text{  }\!\!'\!\!\text{ }}{\text{second}}\]
    So, the time to go up the escalator (“seconds per escalator”) is \[t=\frac{120}{5}=24\]second


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