RAJASTHAN ­ PET Rajasthan PET Solved Paper-2001

  • question_answer
    If\[\overrightarrow{A}=2\hat{i}-2\hat{j}-\hat{k}\]and\[\overrightarrow{B}=-\hat{i}+3\hat{j}+2\hat{k},\]then \[A\times B\]is equal to

    A)  \[\hat{i}+2\hat{j}-4\hat{k}\]     

    B)  \[-\hat{i}-3\hat{j}+4\hat{k}\]

    C)  \[-\hat{i}-5\hat{j}+4\hat{k}\]    

    D)  \[-2\hat{i}-\hat{j}+\hat{k}\]

    Correct Answer: B

    Solution :

     \[\overrightarrow{A}=2\hat{i}-2\hat{j}-\hat{k},\overrightarrow{B}=-\hat{i}+3\hat{j}+2\hat{k}\] \[\therefore \] \[\overrightarrow{A}\times \overrightarrow{B}=\left| \begin{matrix}    {\hat{i}} & {\hat{j}} & {\hat{k}}  \\    2 & -2 & -1  \\    -1 & 3 & 2  \\ \end{matrix} \right|\] \[=\hat{i}(-4+3)-\hat{j}(4-1)+\hat{k}(6-2)\] \[=-\hat{i}-3\hat{j}+4\hat{k}\]


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