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

  • question_answer
    A point moves in a straight line so that its displacement x metre at time t second is given by \[{{x}^{2}}=1+{{t}^{2}}\]. Its acceleration in \[m{{s}^{2}}\] at time second is

    A) \[\frac{1}{{{x}^{3}}}\]

    B) \[\frac{1}{x}\,-\frac{1}{{{x}^{2}}}\]

    C) \[-\frac{t}{{{x}^{2}}}\]

    D) \[\frac{1}{x}\,-\,\frac{{{t}^{2}}}{{{x}^{3}}}\]

    Correct Answer: D

    Solution :

    [d] \[{{x}^{2}}=(1+{{t}^{2}})\] or \[x={{(1\text{ }+\text{ }{{t}^{2}})}^{1/2}}\]
    Velocity, \[\frac{dx}{dt}=\,\frac{1}{2}\,{{(1+\,{{t}^{2}})}^{-1/2}}\times \,2t\]
                \[=t{{(1+\,{{t}^{2}})}^{-1/2}}\]
    Acceleration, \[\frac{{{d}^{2}}x}{d{{t}^{2}}}\,=t\left( -\frac{1}{2} \right)\,\times \,{{\left( 1+{{t}^{2}} \right)}^{-3/2}}\]
                \[\times \,2t+{{(1+{{t}^{2}})}^{-1/2}}\]
    \[=\,\frac{1}{x}-\frac{{{t}^{2}}}{{{x}^{3}}}\]


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