KVPY Sample Paper KVPY Stream-SX Model Paper-31

  • question_answer
    Find the magnitude of projection of vector \[2\hat{i}+3\hat{j}+\hat{k},\] on a vector which is perpendicular to the plane containing vectors \[\hat{i}+\hat{j}+\hat{k}\] and \[\hat{i}+2\hat{j}+3\hat{k}.\]

    A) \[\frac{\sqrt{3}}{\sqrt{2}}\]

    B) \[\frac{\sqrt{2}}{\sqrt{3}}\]

    C) \[\frac{4}{\sqrt{3}}\]     

    D) \[\frac{2\sqrt{2}}{\sqrt{3}}\]

    Correct Answer: A

    Solution :

    Normal vector to the plane containing\[\hat{i}+\hat{j}+\hat{k}\] and \[\hat{i}+2\hat{j}+3\hat{k}\] is
    \[\overrightarrow{n}=\left( \hat{i}+\hat{j}+\hat{k} \right)\times \left( \hat{i}+2\hat{j}+3\hat{k} \right)\]
    \[\overrightarrow{n}=\hat{i}-2\hat{j}+\hat{k}\]
    projection of\[(2\hat{i}+3\hat{j}+\hat{k})\]on\[\vec{n}\]
    \[=\left| \frac{(2\hat{i}+3\hat{j}+\hat{k}).(\hat{i}-2\hat{j}+\hat{k})}{\sqrt{1+4+1}} \right|\]
    \[=\frac{3}{\sqrt{6}}=\sqrt{\frac{3}{2}}.\]


You need to login to perform this action.
You will be redirected in 3 sec spinner