NEET AIPMT SOLVED PAPER SCREENING 2007

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

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

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

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

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

    Correct Answer: A

    Solution :

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


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