J & K CET Engineering J and K - CET Engineering Solved Paper-2009

  • question_answer
    A body, possessing kinetic energy T, moving on a rough horizontal surface, is stopped in a distance y. The frictional force exerted on the. body is

    A)  \[Ty\]

    B)  \[\frac{\sqrt{T}}{y}\]

    C)  \[\frac{T}{y}\]

    D)  \[\frac{T}{\sqrt{y}}\]

    Correct Answer: C

    Solution :

    A block of mass m is moving initially with velocity u on a rough surface and due to friction, it comes to rest after covering a distance s Retarding force \[ma=\mu \,\,mg\] \[\therefore \] \[a=\mu g\] From         \[{{v}^{2}}={{u}^{2}}-2as\] \[\Rightarrow \] \[0={{u}^{2}}-2\mu gs\] \[\frac{2T}{m}=2\mu gy\] ?..(i) \[\left[ As\,\,T=\frac{1}{2}m{{u}^{2}} \right]\] Now, frictional force / =p, mg          ...(ii) ie, from Eqs. (i) and (ii), we get \[f=\frac{T}{y}\]


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