The resultant of two vectors A and B is C. If the magnitude of B is doubled, the new resultant vector becomes perpendicular to A. Then the magnitude of C is (a) B (b) 2B (c) 3B (d) 4B

Answer: (a). (A + 2B) ⊥ A: A² + 2ABcos θ = 0. C² = A² + B² + 2ABcos θ = (A² + 2ABcos θ) + B² = B² C = B So the answer is (a) B.

The resultant of two vectors A and B is C. If the magnitude of B is… | MHT CET 2026 (12 May, Shift 2)

Q6MHT CET 2026 · 12 MAY · SHIFT 2Medium

Addition & Subtraction of Vectors

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

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Answer: (a)

$(\vec{A} + 2\vec{B}) \perp \vec{A}$ : $A^2 + 2AB\cos\theta = 0$ .
$C^2 = A^2 + B^2 + 2AB\cos\theta = (A^2 + 2AB\cos\theta) + B^2 = B^2$
$C = B$
So the answer is (a) $B$ .

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Addition & Subtraction of Vectors question from MHT CET 2026 (12 May, Shift 2)

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