JAMIA MILLIA ISLAMIA Jamia Millia Islamia Solved Paper-2010

  • question_answer
        A particle moves in\[X-Y\]plane under the influence of a force\[\overrightarrow{F}\]such that its instantaneous momentum is\[\overrightarrow{P}=\hat{i}2\cos t+\hat{j}2\sin t\]. What is the angle between the force and instantaneous momentum?

    A)  \[0{}^\circ \]                                     

    B)  \[180{}^\circ \]

    C)  \[90{}^\circ \]                                  

    D)  \[45{}^\circ \]

    Correct Answer: C

    Solution :

                    Here, \[\overrightarrow{P}=\hat{i}2\cos t+\hat{j}2\sin t\] \[\overrightarrow{F}=\frac{d\overrightarrow{P}}{dt}=-2\hat{i}\sin t+2\hat{j}\cos t\] \[\overrightarrow{F}.\overrightarrow{P}=(-2\hat{i}\sin t+2\hat{j}\cos t).(2\hat{i}\cos +2\hat{j}\sin t)\]                 \[=-4\sin t\cos t+4\sin t\cos t\] Therefore,     \[\theta =90{}^\circ \]


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