JEE Main & Advanced Physics Vectors Question Bank Topic Test - Vectors

  • question_answer
    If  \[\vec{a}\times \vec{b}\,+\vec{c}=0,\] then \[\vec{a}\times \vec{b}\,\] is

    A) \[\vec{a}\times \vec{b}\]

    B) \[\vec{c}\times \vec{b}\,\]

    C) \[\vec{a}\times \vec{c}\]

    D) None of these

    Correct Answer: A

    Solution :

    [a] \[\vec{a}\,+\vec{b}\,+\vec{c}=0\]
    \[\therefore \]      \[\vec{a}\,+\vec{c}=-\vec{b}\]
    \[\therefore \]      \[(\vec{a}\,+\vec{c})\,\times \,\vec{b}\,=-\vec{b}\,\times \,\vec{b}=0\]
    or         \[(\vec{a}\,\times \,\vec{b})\,+\,(\vec{c}\times \,\vec{b})=0\]
    or         \[\vec{a}\times \,\vec{b}\,=\vec{b}\times \,\vec{c}\]


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