KVPY Sample Paper KVPY Stream-SX Model Paper-21

  • question_answer
    A block of mass m is pushed across a rough surface by an applied force F, directed at an angle \[\theta \] relative to the horizontal as shown. The block experiences a friction force \[f\] in the opposite direction. What is the coefficient of friction between the block and the surface?

    A) \[\frac{mg}{F\,\,\sin \phi }\]

    B) \[\frac{f}{F\,\,\sin \phi +mg}\]

    C) \[\frac{f}{mg}\] 

    D) \[\frac{mg}{f}\]

    Correct Answer: B

    Solution :

    the key to finding the coefficient of friction \[\mu \]is in calculating the correct normal force acting on the block
    Free body diagram
    Block does not move in y direction
    \[\therefore {{a}_{y}}=0\]
    \[\therefore N=F\sin \phi +mg\]
    \[\mu =\frac{{{F}_{friction}}}{N}=\frac{f}{F\sin \phi +mg}\]

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