RAJASTHAN ­ PET Rajasthan PET Solved Paper-2004

  • question_answer
    The projection of vector\[2\hat{i}+3\hat{j}-2\hat{k}\] on the vector \[\hat{i}+2\hat{j}+3\hat{k}\]is

    A)  \[\frac{1}{\sqrt{14}}\]

    B)  \[\frac{2}{\sqrt{14}}\]

    C)  \[\frac{2}{\sqrt{17}}\]            

    D)  None of these

    Correct Answer: B

    Solution :

     Let      \[\overrightarrow{a}=2\hat{i}+3\hat{j}-2\hat{k}\] and      \[\overrightarrow{b}=\hat{i}+2\hat{j}+3\hat{k}\] Projection of\[\overrightarrow{a}\]on \[\overrightarrow{b}=\frac{\overrightarrow{a}.\overrightarrow{b}}{|\overrightarrow{b}|}\] \[=\frac{(2\hat{i}+3\hat{j}-2\hat{k}).(\hat{i}+2\hat{j}+3\hat{k})}{\sqrt{{{1}^{2}}+{{2}^{2}}+{{3}^{2}}}}\] \[=\frac{2+6-6}{\sqrt{1+4+9}}\] \[=\frac{2}{\sqrt{14}}\]


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