Manipal Engineering Manipal Engineering Solved Paper-2015

  • question_answer
    Solution of the differential equation \[d\sqrt{\frac{{{m}_{2}}}{{{m}_{1}}+{{m}_{2}}}}\]+?is

    A) \[d\sqrt{\frac{2{{m}_{2}}}{{{m}_{1}}+{{m}_{2}}}}\]         

    B) \[d\sqrt{\frac{2{{m}_{1}}}{{{m}_{1}}+{{m}_{2}}}}\]

    C) \[=20m{{s}^{-1}}\]          

    D) \[(\text{take}\,g=10\text{ }m{{s}^{-}}^{2})\]

    Correct Answer: C

    Solution :

    We have,\[x={{e}^{xy\frac{dy}{dx}}}\]\[\Rightarrow \]\[\log x=xy\frac{dy}{dx}\] \[\Rightarrow \]\[ydy=\frac{\log x}{x}dx\]\[\Rightarrow \]\[ydy=\log xd(\log x)\] On integrating both sides, we get \[\frac{{{y}^{2}}}{2}=\frac{{{({{\log }_{e}}x)}^{2}}}{2}+C\]\[\Rightarrow \]\[{{y}^{2}}={{({{\log }_{e}}x)}^{2}}+2C\] \[\Rightarrow \]\[y=\pm \sqrt{{{({{\log }_{e}}x)}^{2}}+2C}\]


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