AMU Medical AMU Solved Paper-2006

  • question_answer
    Find the velocity of centre of mass of the system shown in the figure?  \[\left( \frac{2+2\sqrt{3}}{3} \right)\,\overset{\hat{\ }}{\mathop{i}}\,-\frac{2}{3}\overset{\hat{\ }}{\mathop{j}}\,\]                 \[4\overset{\hat{\ }}{\mathop{i}}\,\]

    A) \[\left( \frac{2+2\sqrt{3}}{3} \right)\hat{i}-\frac{2}{3}\hat{j}\]                   

    B) \[4\hat{i}\]

    C)  \[\left( \frac{2-2\sqrt{3}}{3} \right)\,\overset{\hat{\ }}{\mathop{i}}\,-\frac{2}{3}\overset{\hat{\ }}{\mathop{j}}\,\]               

    D)  None of the above

    Correct Answer: A

    Solution :

                     Here, \[{{m}_{1}}=1\,kg,\,{{\vec{v}}_{1}}=2\,\hat{i}\]                 \[{{m}_{2}}=2\,kg,\,{{\vec{v}}_{2}}=2\cos {{30}^{o}}\hat{i}-2\sin {{30}^{o}}\hat{j}\]                 \[{{\vec{v}}_{CM}}=\frac{{{m}_{1}}\,{{{\vec{v}}}_{1}}+{{m}_{2}}{{{\vec{v}}}_{2}}}{{{m}_{1}}+{{m}_{2}}}\]                 \[=\frac{1\times 2\,\hat{i}+2(2\cos {{30}^{o}}\hat{i}-2\sin {{30}^{o}}\hat{j})}{1+2}\]                 \[=\left( \frac{2\,i+2\sqrt{3}}{3} \right)\hat{i}-\frac{2}{3}\hat{j}\]


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