CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2000

  • question_answer
    If\[x=a{{t}^{2}},y=2at,\]at, then\[\frac{{{d}^{2}}y}{d{{x}^{2}}}\]is equal to:

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

    B)         \[-\frac{1}{2a{{t}^{3}}}\]

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

    D)         \[-\frac{a}{2{{t}^{3}}}\]

    E)  zero

    Correct Answer: B

    Solution :

    \[x=a{{t}^{2}},y=2at\] On differentiating w.r.t. t respectively \[\Rightarrow \]               \[\frac{dx}{dt}=2at,\frac{dy}{dt}=2a\] \[\therefore \]  \[\frac{dy}{dx}=\frac{2a}{2at}=\frac{1}{t},\frac{{{d}^{2}}y}{d{{x}^{2}}}=-\frac{1}{{{t}^{2}}}\frac{dt}{dx}\]                 \[=-\frac{1}{{{t}^{2}}}.\frac{1}{2at}=-\frac{1}{2a{{t}^{3}}}\]


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