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JEE Main & Advanced Mathematics Vector Algebra Question Bank Modulus of vector Algebra of vectors

  • question_answer
    What should be added in vector \[\mathbf{a}=3\mathbf{i}+4\mathbf{j}-2\mathbf{k}\] to get its resultant a unit vector i              [Roorkee 1977]

    A) \[-\,2\mathbf{i}-4\mathbf{j}+2\mathbf{k}\]

    B) \[-2\mathbf{i}+4\mathbf{j}-2\mathbf{k}\]

    C) \[2\mathbf{i}+4\mathbf{j}-2\mathbf{k}\]        

    D) None of these

    Correct Answer: A

    Solution :

    Let \[\mathbf{b}\] should be added, then \[\mathbf{a}+\mathbf{b}=\mathbf{i}\] \[\Rightarrow \mathbf{b}=\mathbf{i}-\mathbf{a}=\mathbf{i}-(3\mathbf{i}+4\mathbf{j}-2\mathbf{k})=-2\mathbf{i}-4\mathbf{j}+2\mathbf{k}.\]               


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