JEE Main & Advanced Physics Vectors Question Bank Multiplication of Vectors

  • question_answer
    Two adjacent sides of a parallelogram are represented by the two vectors \[\hat{i}+2\hat{j}+3\hat{k}\] and \[3\hat{i}-2\hat{j}+\hat{k}\]. What is the area of parallelogram                                      [AMU 1997]

    A)                 8             

    B)                 \[8\sqrt{3}\]

    C)                 \[3\sqrt{8}\]      

    D)                 192

    Correct Answer: A

    Solution :

                        Area of parallelogram \[=\overrightarrow{A}\times \overrightarrow{B}\]                                 \[=(\hat{i}+2\hat{j}+3\hat{k})\times (3\hat{i}-2\hat{j}+\hat{k})\]                                 \[=\left| \,\begin{matrix}    {\hat{i}} & {\hat{j}} & {\hat{k}}  \\    1 & 2 & 3  \\    3 & -2 & 1  \\ \end{matrix}\, \right|\]\[=(8)\hat{i}+(8)\hat{j}-(8)\hat{k}\]                                 Magnitude \[=\sqrt{64+64+64}\]=\[8\sqrt{3}\]


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