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

  • question_answer
    If three vectors along coordinate axes represent the adjacent sides of a cube of length b, then the unit vector along its diagonal passing through the origin will be

    A) \[\frac{\hat{i}\,+\,\hat{j}\,+\,\hat{k}}{\sqrt{2}}\]

    B) \[\frac{\hat{i}\,+\,\hat{j}\,+\,\hat{k}}{\sqrt{3b}}\]

    C) \[\hat{i}\,+\,\hat{j}\,+\,\hat{k}\]

    D) \[\frac{\hat{i}\,+\,\hat{j}\,+\,\hat{k}}{\sqrt{3}}\]

    Correct Answer: D

    Solution :

    [d] Diagonal vector \[\vec{A}\,=b\hat{i}+b\hat{j}+b\hat{k}\]
    or         \[A=\sqrt{{{b}^{2}}+{{b}^{2}}+{{b}^{2}}}\,=\,\sqrt{3}\,b\]
    \[\therefore \]      \[\hat{A}\,\,=\frac{{\vec{A}}}{A}=\,\frac{\hat{i}+\hat{j}+\,\hat{k}}{\sqrt{3}}\]
    \[\therefore \]          \[\hat{A}\,=\frac{{\vec{A}}}{A}=\,\frac{\hat{i}+\hat{j}+\hat{k}}{\sqrt{3}}\]


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