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JEE Main & Advanced Physics Vectors Question Bank Multiplication of Vectors

  • question_answer
    If \[\vec{A}\] and \[\vec{B}\] are perpendicular vectors and vector \[\vec{A}=5\hat{i}+7\hat{j}-3\hat{k}\] and \[\vec{B}=2\hat{i}+2\hat{j}-a\hat{k}.\] The value of a is [EAMCET 1991]

    A)                 ? 2         

    B)                 8

    C)                 ? 7         

    D)                 ? 8

    Correct Answer: D

    Solution :

                        For perpendicular vector \[\overrightarrow{A}.\overrightarrow{B}=0\]                                 Þ \[(5\hat{i}+7\hat{j}-3\hat{k}).(2\hat{i}+2\hat{j}-a\hat{k})=0\]                                 Þ \[10+14+3a=0\]\[\Rightarrow \] \[a=-8\]


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