JEE Main & Advanced Mathematics Vector Algebra Question Bank Vector or Cross product of two vectors and its application

  • question_answer
    The vectors \[\mathbf{c},\,\,\,\mathbf{a}=x\mathbf{i}+y\mathbf{j}+z\mathbf{k}\] and \[\mathbf{b}=\mathbf{j}\] are such that       a, c, b form a right handed system, then c is                 [DCE 1999]

    A)                 \[z\mathbf{i}-x\mathbf{k}\]

    B)                 0

    C)                 \[y\mathbf{j}\]

    D)                 \[-z\mathbf{i}+x\mathbf{k}\]

    Correct Answer: A

    Solution :

               Since \[\mathbf{a},\,\mathbf{b},\,\mathbf{c}\] form a right handed system            \[\therefore \,\mathbf{c}=\mathbf{b}\times \mathbf{a}=\mathbf{j}\times (x\mathbf{i}+y\mathbf{j}+z\mathbf{k})\]                      \[=x(\mathbf{j}\times \mathbf{i})+z(\mathbf{j}\times \mathbf{k})=-x\mathbf{k}+z\mathbf{i}=z\mathbf{i}-x\mathbf{k}\].


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