JEE Main & Advanced AIEEE Solved Paper-2004

  • question_answer
    A body of mass m accelerates uniformly from rest to\[{{v}_{1}}\]in time\[{{t}_{1}}\]. The instantaneous power delivered to the body as a function of time t is

    A) \[\frac{m{{v}_{1}}t}{{{t}_{1}}}\]

    B)                        \[\frac{mv_{1}^{2}t}{t_{1}^{2}}\]            

    C)        \[\frac{m{{v}_{1}}{{t}^{2}}}{{{t}_{1}}}\] 

    D)        \[\frac{mv_{1}^{2}t}{{{t}_{1}}}\]

    Correct Answer: B

    Solution :

    Let the constant acceleration of body of mass m is a. From equation of motion \[{{v}_{1}}=0+a{{t}_{1}}\] \[\Rightarrow \]\[a=\frac{{{v}_{1}}}{{{t}_{1}}}t\]                                ...(i) At an Instant t, the velocity v of the body \[v=0+at\] \[v=\frac{{{v}_{1}}}{{{t}_{1}}}t\]                               ...(ii) Therefore, instantaneous power \[p=Fv=mav\]                   \[(\because F=ma)\] \[=m\left( \frac{{{v}_{1}}}{{{t}_{1}}} \right)\times \left( \frac{{{v}_{1}}}{{{t}_{1}}}.t \right)\]         [from Eqs. (i) and (ii)] \[=\frac{mv_{1}^{2}t}{t_{1}^{2}}\]


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