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JEE Main 2024 (4 Apr, Shift 1) · Addition & Subtraction of Vectors

Addition & Subtraction of Vectors question from JEE Main 2024 (4 Apr, Shift 1)

Q13JEE Main 2024 · 4 APR · SHIFT 1Medium

Addition & Subtraction of Vectors

Two forcesF‾1\overline{F}_1 andF‾2\overline{F}_2 are acting on a body. One force has magnitude thrice that of the other force and the resultant of the two forces is equal to the force of larger magnitude. The angle between F⃗1\vec{F}_1 and F⃗2\vec{F}_2 is cos⁡−1(1n)\cos^{-1}\left(\frac{1}{n}\right). The value of ∣n∣|n| is _______.

Numerical answer type. Work it out, then open the answer.

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Answer: 6

  1. Let the forces be FF and 3F3F, resultant R=3FR = 3F.
  2. 9F2=F2+9F2+6F2cos⁡θ⇒cos⁡θ=−169F^2 = F^2 + 9F^2 + 6F^2\cos\theta \Rightarrow \cos\theta = -\frac{1}{6}
  3. So θ=cos⁡−1(−16)\theta = \cos^{-1}\left(-\frac{1}{6}\right), i.e. n=−6n = -6.
  4. Answer: ∣n∣=6|n| = 6
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