NEET Physics Work, Energy, Power & Collision / कार्य, ऊर्जा और शक्ति NEET PYQ-Work Energy Power and Collision

  • question_answer
    A body of mass 1 kg begins to move under the action of a time dependent force \[\vec{F}=(2t\,\mathbf{\hat{i}}\,+3{{t}^{2}}\,\mathbf{\hat{j}})N,\] where \[\mathbf{\hat{i}}\] and \[\mathbf{\hat{j}}\] are unit vectors along x and y axis. What power will be developed by the force at the time t? [NEET - 2016]

    A) \[(2{{t}^{2}}+3{{t}^{3}})W\]

    B) \[(2{{t}^{2}}+4{{t}^{4}})W\]

    C) \[(2{{t}^{3}}+3{{t}^{4}})W\]

    D) \[(2{{t}^{3}}+3{{t}^{5}})W\]

    Correct Answer: D

    Solution :

    [d] \[\vec{F}=2t\hat{i}+3{{t}^{2}}\hat{j}\,\]
                            \[m\frac{d\vec{v}}{dt}\,=2t\hat{i}+3{{t}^{2}}\hat{j}\] \[\,(m=\,1kg)\]
                \[\Rightarrow \] \[\int\limits_{0}^{{\vec{v}}}{d\vec{v}}=\int\limits_{0}^{t}{(2t\hat{i}+3{{t}^{2}}\hat{j})}dt\Rightarrow \vec{v}={{t}^{2}}\hat{i}+{{t}^{3}}\hat{j}\]
                Power \[=\vec{F}.\vec{v}=(2{{t}^{3}}+3{{t}^{5}})W\]


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