NEET Sample Paper NEET Sample Test Paper-47

  • question_answer
    A uniform rope of length \[\ell \] lies on a table. If the coefficient of friction is u, then the maximum length \[{{\ell }_{1}}\] of the part of this rope which can overhang from the edge of the table without slicing down is:

    A) \[\frac{\ell }{\mu }\]                  

    B) \[\frac{\ell }{\mu +1}\]   

    C) \[\frac{\mu \ell }{\mu +1}\]                   

    D) \[\frac{\mu \ell }{\mu -1}\]

    Correct Answer: C

    Solution :

    Rope of length £ has mass = m \[\operatorname{Rope} of hanging length\,{{\ell }_{1}} has mass = \frac{m}{\ell }{{\ell }_{1}}\] In equilibrium Weight of hanging part = force of friction on the part of rope \[=\frac{\operatorname{m}}{\ell }{{\ell }_{1}}\,\operatorname{g}=\frac{\mu \operatorname{m}}{\operatorname{g}}\left( \ell -{{\ell }_{1}} \right)\operatorname{g}\] \[={{\ell }_{1}}\,\operatorname{g}=\mu \operatorname{m}\operatorname{g}-\mu \ell g\] \[{{\ell }_{1}}=\left[ \frac{\mu }{1+\mu } \right]\ell \]


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