JEE Main & Advanced Physics Work, Energy, Power & Collision / कार्य, ऊर्जा और शक्ति Question Bank Self Evaluation Test - Work, Energy and Power

  • question_answer
    A particle of mass m is moving in a circular path of constant radius r such that its centripetal acceleration \[{{a}_{c}}\] is varying with time t as \[{{a}_{c}}={{k}^{2}}r{{t}^{2}}\] where k is a constant. The power delivered to the particles by the force acting on it is

    A) \[2\pi m{{k}^{2}}{{r}^{2}}t\]

    B) \[m{{k}^{2}}{{r}^{2}}t\]

    C) \[\frac{\left( m{{k}^{4}}{{r}^{2}}{{t}^{5}} \right)}{3}\]

    D) zero

    Correct Answer: B

    Solution :

    [b] The centripetal acceleration \[{{a}_{c}}={{k}^{2}}\,r\,{{t}^{2}}or\,\frac{{{v}^{2}}}{r}={{k}^{2}}r{{t}^{2}}\,\,\,\,\therefore v=krt\] So, tangential acceleration, \[{{\operatorname{a}}_{t}} = \frac{dv}{dt} = kr\] Work is done by tangential force. Power \[= {{F}_{i}}.v.cos 0{}^\circ  = \left( m{{a}_{t}} \right)\left( krt \right) = \left( mkr \right)\left( krt \right)\] \[=m{{k}^{2}}{{r}^{2}}t\]


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