JEE Main & Advanced Physics Vectors Question Bank Fundamentals of Vectors

  • question_answer The angle between the two vectors\[\vec{A}=3\hat{i}+4\hat{j}+5\hat{k}\]and \[\vec{B}=3\hat{i}+4\hat{j}+5\hat{k}\] is                                                           [DPMT 2000]

    A)            60°

    B)            Zero

    C)            90°

    D)            None of these

    Correct Answer: D

    Solution :

                 \[\cos \theta =\frac{\overrightarrow{A}.\overrightarrow{B}}{|A||B|}=\frac{9+16+25}{\sqrt{9+16+25}\sqrt{9+16+25}}\]=\[\frac{50}{50}=1\] Þ\[\cos \theta =1\] \[\therefore \] \[\theta ={{\cos }^{-1}}(1)\]

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