JEE Main & Advanced Physics Motion in a Straight Line / सरल रेखा में गति JEE PYQ - One Dimensional Motion

  • question_answer
    A particle located at\[x=0\]at time\[t=0\], starts moving along the positive x-direction with a velocity v that varies as\[v=\alpha \sqrt{x}\]. The displacement of the particle varies with time as                                             [AIEEE 2006]

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

    B) \[t\]

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

    D) \[{{t}^{3}}\]

    Correct Answer: A

    Solution :

    [a] The variation of the velocity is given as.
    \[v=\alpha \sqrt{x}\]
    We can write it as \[\frac{dx}{dt}=\alpha \sqrt{x}\]         \[\left( \because v=\frac{dx}{dt} \right)\]
    \[\Rightarrow \] \[\frac{dx}{\sqrt{x}}=\alpha dt\]
    Perform integration within the limit \[\int_{0}^{x}{\frac{dx}{\sqrt{x}}}=\int_{0}^{t}{\alpha \,dt}\]
    [\[\because \]at\[t=0,\text{ }x=0\]and let at any time t, particle be at\[x\]]
    \[\Rightarrow \]   \[\left. \frac{{{x}^{1/2}}}{1/2} \right|_{0}^{x}=\alpha t\]       
    \[\Rightarrow \]   \[{{x}^{1/2}}=\frac{\alpha }{2}t\]
    \[\Rightarrow \]   \[x=\frac{{{\alpha }^{2}}}{4}\times {{t}^{2}}\]\[\Rightarrow \]\[x\propto {{t}^{2}}\]


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