NEET Sample Paper NEET Sample Test Paper-3

  • question_answer
    The unit vector perpendicular to both, \[\hat{i}+\hat{j}\]and \[\hat{j}-\hat{k}\] is:

    A)  \[\frac{1}{\sqrt{3}}(\hat{i}+\hat{j}-\hat{k})\]

    B)  \[\frac{1}{\sqrt{3}}(-\hat{i}+\hat{j}+\hat{k})\]

    C)  \[\frac{1}{\sqrt{3}}(\hat{i}-\hat{j}+\hat{k})\]

    D)  \[\frac{1}{\sqrt{3}}(\hat{i}+\hat{j}+\hat{k})\]

    Correct Answer: B

    Solution :

        As       \[\hat{n}=\frac{A\times B}{|A\times B|}\] \[A\times B\left| \begin{matrix}    {\hat{i}} & {\hat{j}} & {\hat{k}}  \\    1 & 1 & 0  \\    0 & 1 & -1  \\ \end{matrix} \right|=\hat{i}\,(-1-0)-\hat{j}(-1-0)+\hat{k}(1-0)\] \[=-\hat{i}+\hat{j}+\hat{k}\]                 \[\therefore \]  \[|A\times B|=\sqrt{3},\] \[\hat{n}=\frac{1}{\sqrt{3}}(-\hat{i}+\hat{j}+\hat{k})\]


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