NEET Physics Vectors NEET PYQ-Vectors

  • question_answer
    \[\vec{A}\] and \[\vec{B}\] are two vectors and \[\theta \] is the angle between them, if \[|\vec{A}\times \vec{B}|=\sqrt{3}\,(\vec{A}\,\centerdot \,\vec{B})\] the value of \[\theta \] is:                                      [AIPMT (S) 2007]

    A) \[{{60}^{o}}\]

    B) \[{{45}^{o}}\]

    C) \[{{30}^{o}}\]

    D) \[{{90}^{o}}\]

    Correct Answer: A

    Solution :

    Key Idea: \[\vec{A}\times \vec{B}=AB\sin \theta \] and \[\vec{A}\,\,\centerdot \,\,\vec{B}=AB\cos \theta .\]
    Given,   \[\left| \vec{A}\times \vec{B} \right|=\sqrt{3}\,(\vec{A}\,\centerdot \,\,\vec{B})\]
    \[\Rightarrow \]   \[AB\sin \theta =\sqrt{3}\,AB\cos \theta \]
    \[\Rightarrow \]   \[\tan \theta =\sqrt{3}\]
    \[\therefore \]      \[\theta ={{60}^{o}}\]


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