JEE Main & Advanced Physics Motion in a Straight Line / सरल रेखा में गति Question Bank Topic Test - One Dimensional Motion

  • question_answer
    A particle is moving rectilinearly with acceleration a, whose value is given as a function of distance by the equation \[a=\alpha \sqrt{x},\] find displacement as a function of time. [At \[t=0,\] particle is at rest at \[x=0\]]

    A) \[\frac{4a{{t}^{3}}}{2}\]

    B) \[\left( \frac{\sqrt{\alpha }}{6} \right)t\]

    C) \[\left( \frac{{{\alpha }^{2}}}{36} \right){{t}^{4}}\]

    D) \[\left( \frac{{{\alpha }^{2}}}{144} \right){{t}^{4}}\]

    Correct Answer: D

    Solution :

    [d] \[a=\alpha \sqrt{x}\]
    \[\Rightarrow \]            \[\frac{vdv}{dx}=\alpha \sqrt{x}\] \[\Rightarrow \]            \[vdv=\alpha \sqrt{x}dx\]
    \[\int_{0}^{v}{vdv}=\int_{0}^{x}{\alpha \sqrt{x}}dx\]
    \[\Rightarrow \]            \[\frac{{{v}^{2}}}{2}=\frac{(\alpha {{x}^{3/2}})}{(3/2)}\]
    \[\Rightarrow \]            \[{{v}^{2}}=\frac{4\alpha {{x}^{3/2}}}{3}\] \[\Rightarrow \] \[v=\left( \sqrt{\frac{4\alpha }{3}} \right){{x}^{3/4}}\]
    \[\Rightarrow \]            \[\frac{dx}{dt}=\left( \sqrt{\frac{4\alpha }{3}} \right){{x}^{3/4}}\] \[\Rightarrow \] \[\frac{dx}{{{x}^{3/4}}}=\left( \sqrt{\frac{4\alpha }{3}} \right)dt\]
    \[\Rightarrow \]            \[4{{x}^{1/4}}=\left( \sqrt{\frac{4\alpha }{3}} \right)t\] \[\Rightarrow \] \[x=\frac{{{\alpha }^{2}}{{t}^{4}}}{144}\]


You need to login to perform this action.
You will be redirected in 3 sec spinner