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

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

    A) \[{{t}^{3/4}}\]

    B) \[{{t}^{3/2}}\] 

    C) \[{{t}^{1/4}}\]

    D) \[{{t}^{1/2}}\]

    Correct Answer: B

    Solution :

    [b] We know that \[\operatorname{F}\times v = Power\] \[\therefore \text{ }F\times v=c\]where c = constant \[a\therefore m\frac{dv}{dt}\times v=c~~~\left( \therefore F=ma=\frac{mdv}{dt} \right)\]\[\therefore m\int\limits_{0}^{v}{vdv=c\int\limits_{0}^{t}{dt}\therefore \frac{1}{2}m{{v}^{2}}=ct}\] \[\therefore v=\sqrt{\frac{2c}{m}}\times {{t}^{{}^{1}/{}_{2}}}\] \[\therefore \frac{dx}{dt}=\sqrt{\frac{2c}{m}}\times {{t}^{{}^{1}/{}_{2}}}where\,\,v=\frac{dx}{dt}\] \[\therefore \int\limits_{0}^{x}{dx=\sqrt{\frac{2c}{m}}\times \int\limits_{0}^{t}{{{t}^{{}^{1}/{}_{2}}}}}dt\] \[x=\sqrt{\frac{2c}{m}}\times \frac{2{{t}^{{}^{3}/{}_{2}}}}{3}\Rightarrow x\propto {{t}^{{}^{3}/{}_{2}}}\]


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