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CMC Medical CMC-Medical Ludhiana Solved Paper-2008

  • question_answer
    An open knife edge of mass m is dropped from a height h on a wooden floor. If the blade penetrates s into the wood the average resistance offered by the wood to the blade is

    A)  \[Mg\]                                

    B)  \[Mg\left( \frac{h}{s} \right)\]

    C)  \[Mg\left( 1-\frac{h}{s} \right)\]                             

    D)  \[Mg{{\left( 1+\frac{h}{s} \right)}^{2}}\]

    Correct Answer: B

    Solution :

                    Velocity at the time when knife edge strikes wooden floor is\[\sqrt{2gh}\]. The velocity of \[\sqrt{2gh}\] is reduced to zero in a distances. Ifp is the average retardation, then by work-energy theorem, we have \[0-\frac{1}{2}m{{v}^{2}}=-Fs\] \[\Rightarrow \]                               \[F=Mg\left( \frac{h}{s} \right)\]


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