JEE Main & Advanced Physics Vectors Sample Paper Topic Test- Vectors

  • question_answer
    The unit vector parallel to the resultant of the vectors \[\overrightarrow{A}=4\hat{i}+3j+6\hat{k}\] and \[\overrightarrow{B}=-\hat{i}+3j-8\hat{k}\] is

    A) \[\frac{1}{7}(3\hat{i}+6j-2\hat{k})\]

    B) \[\frac{1}{7}(3\hat{i}+6j+2\hat{k})\]

    C) \[\frac{1}{49}(3\hat{i}+6j-2\hat{k})\]

    D) \[\frac{1}{49}(3\hat{i}-6j+2\hat{k})\]

    Correct Answer: A

    Solution :

    [a] Resultant of vectors \[\vec{A}\] and \[\vec{B}\]
    \[\vec{R}=\vec{A}+\vec{B}=4\hat{i}+3\hat{j}+6\hat{k}-\hat{i}+3\hat{j}-8\hat{k}\]
    \[\vec{R}=3\hat{j}+6\hat{j}-2\hat{k}\]
    \[\hat{R}=\frac{{\vec{R}}}{|\vec{R}|}=\frac{3\hat{i}+6\hat{j}-2\hat{k}}{\sqrt{{{3}^{2}}+{{6}^{2}}+{{(-2)}^{2}}}}\]\[=\frac{1}{7}(3\hat{i}+6\hat{j}-2\hat{k})\]


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