Manipal Medical Manipal Medical Solved Paper-2012

  • question_answer
    A body of mass\[{{m}_{1}}=4\]kg moves at\[5\hat{i}\text{ }m/s\]and another body of mass\[{{m}_{2}}=2\]kg moves at\[10\hat{i}\] m/s. The kinetic energy of centre of mass is

    A)  \[\frac{200}{3}J\]

    B)  \[\frac{500}{3}J\]

    C)  \[\frac{400}{3}J\]

    D)  \[\frac{800}{3}J\]

    Correct Answer: C

    Solution :

     \[{{v}_{CM}}=\frac{{{m}_{1}}\frac{d{{r}_{1}}}{dt}+{{m}_{2}}\frac{d{{r}_{2}}}{dt}}{{{m}_{1}}+{{m}_{2}}}\] \[=\frac{4\times 5\hat{i}+2\times 10\hat{i}}{4+2}\] \[{{v}_{CM}}=\frac{40\hat{i}}{6}=\frac{20}{3}\hat{i}\] The kinetic energy \[K=\frac{1}{2}m{{v}^{2}}\] \[=\frac{1}{2}\times (4+2)\times \frac{20\times 20}{3\times 3}\] \[=\frac{1}{2}\times 6\times \frac{20\times 20}{3\times 3}\] \[K=\frac{400}{3}J\]


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