JEE Main & Advanced Sample Paper JEE Main Sample Paper-9

  • question_answer
    The time taken by a transverse pulse to travel the full length of a uniform rope of mass 0.1 kg & length 2.45 m hanging from the ceiling, is

    A)  1s                          

    B)  0.5s     

    C)  2s                          

    D)  1.5s

    Correct Answer: A

    Solution :

    At a distance y from bottom end consider a string element of length dy. Tension at this height is, \[T=\frac{m}{l}\times yg\] So, \[\frac{dy}{dt}=\] velocity of wave \[=\sqrt{\frac{T}{\mu }=}\sqrt{gy}\] \[\Rightarrow \]\[\int\limits_{0}^{2.45}{\frac{dy}{\sqrt{gy}}=\int\limits_{0}^{t}{dt}}\]\[\Rightarrow \]\[t=1s\]


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