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MHT CET 2020 (16 Oct, Shift 2) · Addition & Subtraction of Vectors

Addition & Subtraction of Vectors question from MHT CET 2020 (16 Oct, Shift 2)

Q25MHT CET 2020 · 16 OCT · SHIFT 2Medium

Addition & Subtraction of Vectors

The resultant of two vector $\mathbf{A}$ and $\mathbf{B}$ is $\mathbf{C}$ . If the magnitude of $\mathbf{B}$ is doubled, the new resultant vector becomes perpendicular to A. Then, the magnitude of $\mathbf{C}$ is

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Answer: (b)

$(\vec{A} + 2\vec{B}) \cdot \vec{A} = 0 \Rightarrow A^2 + 2AB\cos\theta = 0$
$C^2 = A^2 + B^2 + 2AB\cos\theta = B^2 \Rightarrow C = B$
So the answer is (b) B.

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