AFMC AFMC Solved Paper-2002

  • question_answer
    A machine delivering constant power moves a body along straight line. The distance move by the body in time f is proportional to:

    A) t3/4                                         

    B)  t3/2

    C) \[\sqrt{t}\]                         

    D) t

    Correct Answer: B

    Solution :

    Key Idea: Power is defined as amount of work done per unit time. Power is defined as time rate of doing work  i.e.,            \[P=\frac{dW}{dt}\] Also work down = force \[\times \] displacement = F. d and force = mass \[\times \] acceleration = ma \[\therefore \]     \[P=\frac{Fd}{t}=\frac{ma.d}{t}\]  Also, distance = speed \[\times \] time i.e., \[d=vt\Rightarrow v=\frac{d}{t}\] and acceleration, \[a=\frac{v}{t}\] \[\therefore \]         \[P=\frac{m}{{{t}^{2}}}vd\]                   \[P=\frac{m}{{{t}^{2}}}.\frac{d}{t}.d=\frac{m{{d}^{2}}}{{{t}^{3}}}\]\[\Rightarrow \]       \[{{d}^{2}}\propto {{t}^{3}}\]                \[\Rightarrow \]     \[d\propto {{t}^{3/2}}\]                                                         


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