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

  • question_answer
    A unit vector perpendicular to the plane containing the vectors \[\mathbf{i}-\mathbf{j}+\mathbf{k}\] and \[-\mathbf{i}+\mathbf{j}+\mathbf{k}\] is               [Karnataka CET 2005]

    A)                 \[\frac{\mathbf{i}-\mathbf{j}}{\sqrt{2}}\]

    B)                 \[\frac{\mathbf{i}+\mathbf{k}}{\sqrt{2}}\]

    C)                 \[\frac{\mathbf{j}-\mathbf{k}}{\sqrt{2}}\]

    D)                 \[\frac{\mathbf{i}+\mathbf{j}}{\sqrt{2}}\]

    Correct Answer: D

    Solution :

               Unit vectors perpendicular to the plane of \[\mathbf{a}\] and \[\mathbf{b}\]          = \[\pm \frac{\mathbf{a}\times \mathbf{b}}{|\mathbf{a}\times \mathbf{b}|}\]                    \[\therefore \] Required vector is \[\pm \frac{(\mathbf{i}-\mathbf{j}+\mathbf{k})\times (-\mathbf{i}+\mathbf{j}+\mathbf{k})}{\left| (\mathbf{i}-\mathbf{j}+\mathbf{k})\times (-\mathbf{i}+\mathbf{j}+\mathbf{k}) \right|}\]                   \[=\pm \frac{(-(\mathbf{i}+\mathbf{j}))}{\sqrt{2}}i.e.,\ \frac{-(\mathbf{i}+\mathbf{j})}{\sqrt{2}}\] and \[\frac{\mathbf{i}+\mathbf{j}}{\sqrt{2}}\].


You need to login to perform this action.
You will be redirected in 3 sec spinner