CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2008

  • question_answer
    A spherical iron ball of radius 10 cm, coated with a layer of ice of uniform thickness, melts at a rate of\[100\,\pi \,c{{m}^{3}}/min\]. The rate at which the thickness of decreases when the thickness of ice is 5 cm, is

    A)  1 cm/min     

    B)         2 cm/min

    C) \[\frac{1}{376}cm/min\]   

    D)         5 cm/min

    E)  3 cm/min

    Correct Answer: A

    Solution :

    Given, \[\frac{dV}{dt}=100\pi \,c{{m}^{3}}/\min \] \[\therefore \] \[\frac{d}{dt}\left( \frac{4}{3}\pi {{r}^{3}} \right)=100\pi \] \[\Rightarrow \]               \[3{{r}^{2}}\frac{dr}{dt}=\frac{300\pi }{4\pi }\] \[\Rightarrow \]               \[{{\left( \frac{dr}{dt} \right)}_{(r=5)}}=\frac{300}{4\times 3\times 25}\] \[=1\text{ }cm/min\]


You need to login to perform this action.
You will be redirected in 3 sec spinner