JEE Main & Advanced Sample Paper JEE Main Sample Paper-43

  • question_answer
    A chord is used to lower vertically a block of mass M a distance d at a constant downward acceleration of \[\frac{g}{4}\]. Then, the work done by the chord on the block is

    A)  \[\frac{Mgd}{4}\]                  

    B)  \[\frac{-Mgd}{4}\]

    C)  \[\frac{3Mgd}{4}\]                

    D)  \[\frac{-3Mgd}{4}\]

    Correct Answer: C

    Solution :

     Tension in the chord is \[\frac{1}{2}\,m{{v}^{2}}=16\,\,J\]in upward direction, since Chord is displaced in the downward direction, so \[v=4\,m{{s}^{-1}}\] \[Mg\,\,\sin \,\,\theta \]   \[Mg\,\,\sin \theta \times \frac{h}{2}Mg\,\cos \,\theta \,\times r\] Here, negative sign shows that T and dare in the opposite directions.

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