NEET Sample Paper NEET Sample Test Paper-70

  • question_answer
    The speed \[\left( \nu  \right)\] of ripples on the surface of water depends on surface tension\[\left( \sigma  \right)\], density \[\left( \rho  \right)\] and wavelength\[\left( \lambda  \right)\]. The square of speed \[\left( \nu  \right)\] is proportional to

    A) \[\frac{\sigma }{\rho \lambda }\]                   

    B)   \[\frac{\rho }{\sigma \lambda }\]

    C) \[\frac{\lambda }{\sigma \rho }\]                               

    D) \[\rho \lambda \sigma \,\]

    Correct Answer: A

    Solution :

    \[Let\,\,\,\nu \propto \,\,{{\sigma }^{a}}{{\rho }^{b}}{{\lambda }^{c}}\] Equating dimensions on both sides, \[\left[ {{M}^{0}}{{L}^{1}}{{T}^{-1}} \right]\propto {{\left[ {{M}^{T-2}} \right]}^{a}}\,{{\left[ M{{L}^{-3}} \right]}^{b}}{{\left[ L \right]}^{c}}\] Equating the powers of M, L, T on both sides, we get \[\operatorname{a}+b=0\] \[-\,3b+c=1\] Solving, we get \[a=\frac{1}{2},\,\,b=-\frac{1}{2},\,\,c=-\frac{1}{2}\] \[\therefore \,\,\,\,\,\nu \propto {{\sigma }^{1/2}}{{\rho }^{-1/2}}{{\lambda }^{-1/2}}\] \[\therefore \,\,\,\,\,\nu \propto \frac{\sigma }{\rho \lambda }\]


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