CMC Medical CMC-Medical VELLORE Solved Paper-2014

  • question_answer
    A body of specific heat\[0.2\,kcal\text{/}kg{}^\circ C\]is heated through\[100{}^\circ C\]. The percentage increase in its mass is

    A)  \[9%\]                                 

    B)  \[9.3\times {{10}^{-11}}%\]

    C)  \[10%\]                              

    D)  None of these

    Correct Answer: B

    Solution :

                    Heat taken by the given body \[=mc\,\Delta \theta \] (specific heat of body \[=0.2\text{ }kcal\text{/}kg\text{ }{}^\circ C,\] final temperature of the body)\[=100{}^\circ C\] \[\Delta E=m\times 0.2\times 100\]       \[=20\,m\,kcal\]       \[=20\,m\times 4.2\times {{10}^{3}}J\] Now, gain in mass is given by \[\Delta m=\frac{\Delta E}{{{c}^{2}}}\]        \[=\frac{20\,m\times 4.2\times {{10}^{3}}}{{{(3\times {{10}^{8}})}^{2}}}\] Therefore percentage increase in mass is given by \[=\frac{\Delta m}{m}\times 100\] \[=\frac{20\,m\times 4.2\times {{10}^{3}}\times 100}{{{(3\times {{10}^{8}})}^{2}}\times m}\] \[=9.3\times {{10}^{-11}}%\]


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