BHU PMT BHU PMT (Mains) Solved Paper-2010

  • question_answer

    Directions : In the following question more than one of the answers given may be correct. Select the correct answer and mark it according to the code:

    A string of length L is stretched along the\[x-\]axis and is rigidly clamped at its two ends. It undergoes transverse vibrations. If n is an integer, which of the following relations may represent the shape of the string at any time t? (1) \[y=A\sin \left( \frac{n\pi x}{L} \right)\cos \omega t\] (2) \[y=A\sin \left( \frac{n\pi x}{L} \right)\sin \omega t\] (3) \[y=A\cos \left( \frac{n\pi x}{L} \right)\cos \omega t\] (4) \[y=A\cos \left( \frac{n\pi x}{L} \right)\sin \omega t\]

    A)  1, 2 and 3 are correct

    B)  1 and 2 are correct

    C)   2 and 4 are correct

    D)  1 and 3 are correct

    Correct Answer: B

    Solution :

                     As the string is rigidly clamped at its two ends therefore,\[y=0\]at\[x=0\]. This can be satisfied only by term\[\sin \frac{n\pi x}{L},\]where n is an integer. Hence, option  is correct.


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