J & K CET Medical J & K - CET Medical Solved Paper-2012

  • question_answer
    A certain vector in the\[x-y\]plane has an \[x-\] component of 12 m and a\[y-\]component of 8 m. It is then rotated in the\[x-y\]plane so that its\[x-\]component is halved. Then its new y-component is approximately

    A)  14m           

    B)  13.11m

    C)  10m           

    D)  2.0m

    Correct Answer: B

    Solution :

     Let A be vector in\[x-y\]plane. Its\[x\]and y components are \[{{A}_{x}}=12\text{ }m\] and \[{{A}_{y}}=8\text{ }m\] \[A=\sqrt{A_{x}^{2}+A_{y}^{2}}\] \[=\sqrt{{{(12)}^{2}}+{{(8)}^{2}}}\] \[A=\sqrt{208}\,m\] When the vector is rotated in\[x-y\]plane, then \[x\]component become halved and its new y component \[A_{y}^{}=\sqrt{{{\left( \frac{{{A}_{x}}}{2} \right)}^{2}}+A_{y}^{2}}\] \[\sqrt{208}=\sqrt{{{(6)}^{2}}+A_{y}^{2}}\] \[A_{y}^{}=\sqrt{208-36}\] \[A_{y}^{}=\sqrt{172}\] \[=13.11cm\]


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