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JEE Main & Advanced Sample Paper JEE Main Sample Paper-6

  • question_answer
    A hunter is standing on flat ground between two vertical cliffs that are directly opposite to one another. He is closer to one cliff than the other. He fires a gun and after a while, hears three echoes. The second echo arrives 1.6 s after the first, and the third echo arrives 1.1 s after the Second. Assuming that speed of sound is 343 m/s and that there are no reflections of sound from the ground. Find the distance between the cliffs.

    A)  651 m                                  

    B)  840 m

    C)  460 m                                  

    D)  188 m

    Correct Answer: A

    Solution :

    Let the hunter is at a distance of x and y meters from two cliffs respectively (y > x). The first echo will be heard when the sound reflects from cliff 1 and 2nd echo when reflects, from cliff 2 and 3rd echo will be heard due to the sound which has been reflected twice, once from cliff 1 and then from cliff 2. Then from the given information \[2x=v{{t}_{0}},\]where \[{{t}_{0}}\]is the time after firing at which the person is hearing the first echo. \[2y=v({{t}_{0}}+1.6)\] \[2x+2y=v({{t}_{0}}+1.6+1.1)\]


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