JEE Main & Advanced Physics Vectors Question Bank Multiplication of Vectors

  • question_answer
    The area of the parallelogram whose sides are represented by the vectors \[\hat{j}+3\hat{k}\] and \[\hat{i}+2\hat{j}-\hat{k}\] is

    A)                 \[\sqrt{61}\]sq. unit

    B)                             \[\sqrt{59}\]sq. unit

    C)                 \[\sqrt{49}\]sq. unit       

    D)                 \[\sqrt{52}\]sq. unit

    Correct Answer: B

    Solution :

                        \[\vec{A}=\hat{j}+3\hat{k}\],\[\vec{B}=\hat{i}+2\hat{j}-\hat{k}\]                 \[\vec{C}=\vec{A}\times \vec{B}\]\[=\left| \,\begin{matrix}    {\hat{i}} & {\hat{j}} & {\hat{k}}  \\    0 & 1 & 3  \\    1 & 2 & -1  \\ \end{matrix}\, \right|\]\[=-7\hat{i}+3\hat{j}-\hat{k}\]                 Hence area = \[|\vec{C}|=\sqrt{49+9+1}=\sqrt{59}\,sq\,unit\]


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