JEE Main & Advanced Physics Vectors Question Bank Multiplication of Vectors

  • question_answer
    The value of \[(\overrightarrow{A}+\overrightarrow{B})\,\times (\overrightarrow{A}-\overrightarrow{B})\] is                  [RPET 1991, 2002; BHU 2002]

    A)                 0             

    B)                 \[{{A}^{2}}-{{B}^{2}}\]

    C)                 \[\overrightarrow{B}\times \overrightarrow{A}\]            

    D)                 \[2(\overrightarrow{B}\times \overrightarrow{A})\]

    Correct Answer: D

    Solution :

                        \[(\vec{A}+\vec{B})\times (\vec{A}-\vec{B})\] \[=\vec{A}\times \vec{A}-\vec{A}\times \vec{B}+\vec{B}\times \vec{A}-\vec{B}\times \vec{B}\]                 \[=0-\vec{A}\times \vec{B}+\vec{B}\times \vec{A}-0\]\[=\vec{B}\times \vec{A}+\vec{B}\times \vec{A}=2(\vec{B}\times \vec{A})\]


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