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Question: Answered & Verified by Expert
The value of ' $\lambda$ ' for which the two vectors $\vec{a}=5 \hat{i}+\lambda \hat{j}+\hat{k}$ and $\vec{b}=\hat{i}-2 \hat{j}+\hat{k}$ are perpendicular to each other is
PhysicsMathematics in PhysicsJEE Main
Options:
  • A 2
  • B -2
  • C 3
  • D -3
Solution:
1632 Upvotes Verified Answer
The correct answer is: 3
Hints : For $\vec{a} \perp \vec{b}$
$\begin{aligned}
& \vec{a} \cdot \vec{b}=0 \\
& \text { i.e., } 5-2 \lambda+1=0 \\
& \lambda=3
\end{aligned}$

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