Uttarakhand PMT Uttarakhand PMT Solved Paper-2007

  • question_answer
    A point moves such that its displacement as a function of time is given by \[{{x}^{2}}={{t}^{2}}+1.\] Its acceleration at time t is

    A)  \[\frac{1}{{{x}^{4}}}\]

    B)  \[\frac{t}{{{x}^{2}}}\]

    C)  \[\frac{t}{x}-\frac{{{t}^{2}}}{{{x}^{3}}}\]

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

    Correct Answer: C

    Solution :

     Given, \[{{x}^{2}}={{t}^{2}}+1\] Differentiate, w.r.t. r, we get \[2x=\frac{dx}{dt}=2t\] \[\therefore \] \[v=\frac{dx}{dt}=\frac{t}{x}\] Also, \[a=\frac{dv}{dt}=\frac{x-t\left( \frac{dx}{dt} \right)}{{{x}^{2}}}=\frac{x-\left( \frac{{{t}^{2}}}{x} \right)}{{{x}^{2}}}\] \[\Rightarrow \] \[a=\frac{1}{x}-\frac{{{t}^{2}}}{{{x}^{3}}}\]


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