JEE Main & Advanced Physics Vectors Question Bank Multiplication of Vectors

  • question_answer
    If \[\overrightarrow{A}=3\hat{i}+\hat{j}+2\hat{k}\] and \[\overrightarrow{B}=2\hat{i}-2\hat{j}+4\hat{k}\] then value of \[|\overrightarrow{A}\times \overrightarrow{B}|\,\] will be

    A)                 \[8\sqrt{2}\]      

    B)                 \[8\sqrt{3}\]

    C)                 \[8\sqrt{5}\]      

    D)                 \[5\sqrt{8}\]

    Correct Answer: B

    Solution :

                        \[\overrightarrow{A}\,\times \,\overrightarrow{B}\,=\left| \,\begin{matrix}    \hat{i}\,\, & \hat{j}\,\, & {\hat{k}}  \\    3\,\, & 1\,\, & 2  \\    2\,\,\, & -2\,\,\, & 4  \\ \end{matrix}\, \right|\,\] \[=(1\times 4-2\times -2)\hat{i}+(2\times 2-4\times 3)\hat{j}+(3\times -2-1\times 2)\hat{k}\] \[=8\hat{i}-8\hat{j}-8\hat{k}\]                 \Magnitude of \[\overrightarrow{\text{A}}\,\times \overrightarrow{\text{B}}\,=\,|\overrightarrow{\text{A}}\times \overrightarrow{\text{B}}|\,=\sqrt{{{(8)}^{2}}+{{(-8)}^{2}}+{{(-8)}^{2}}}\,\]                 \[=8\sqrt{3}\]


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