JEE Main & Advanced Physics Work, Energy, Power & Collision / कार्य, ऊर्जा और शक्ति Question Bank Critical Thinking

  • question_answer
    A body is moved along a straight line by a machine delivering constant power. The distance moved by the body in time t is proportional to                         [IIT 1984; BHU 1984, 95; MP PET 1996; JIPMER 2000; AMU (Med.) 1999]

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

    B)             \[{{t}^{3/4}}\]

    C)             \[{{t}^{3/2}}\]         

    D)             \[{{t}^{2}}\]

    Correct Answer: C

    Solution :

                    \[P=Fv=mav=m\left( \frac{dv}{dt} \right)\ v\]Þ \[\frac{P}{m}dt=v\ dv\] Þ\[\frac{P}{m}\times t=\frac{{{v}^{2}}}{2}\]Þ \[v={{\left( \frac{2P}{m} \right)}^{1/2}}{{(t)}^{1/2}}\] Now \[s=\int_{{}}^{{}}{v\ dt=\int_{{}}^{{}}{{{\left( \frac{2P}{m} \right)}^{1/2}}{{t}^{1/2}}dt}}\] \ \[s={{\left( \frac{2P}{m} \right)}^{1/2}}\left[ \frac{2{{t}^{3/2}}}{3} \right]\]Þ \[s\propto {{t}^{3/2}}\]


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