JEE Main & Advanced Mathematics Applications of Derivatives Question Bank Application in Mechanics and Rate Measurer

  • question_answer
    The radius of a cylinder is increasing at the rate of 3 m/sec and its altitude is decreasing at the rate of 4m/sec. The rate of change of volume when radius is 4 meters and altitude is 6 meters is                                         [Kerala (Engg.) 2005]

    A)            \[80\pi \,\]cu. m/sec

    B)            \[144\,\pi \,\]cu. m/sec

    C)            \[80\,\] cu. m/sec

    D)            \[64\,\] cu. m/sec

    E)            \[-80\,\pi \] cu. m/sec

    Correct Answer: A

    Solution :

               \[V=\pi {{r}^{2}}h\]; \[\frac{\partial V}{\partial t}=\pi \left[ 2r\frac{\partial r}{\partial t}h+{{r}^{2}}\frac{\partial h}{\partial t} \right]\]                    \[\frac{\partial V}{\partial t}=\pi \,[2(4)\,(3)\,(6)\,+\,{{(4)}^{2}}(-4)]=\pi \,[144-64]=80\,\pi \text{ }cu\,m/sec\].


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