Vector Algebra Question 10
Question: If the vectors $3 \hat{i}+\lambda \hat{j}+\hat{k}$ and $2 \hat{i}-\hat{j}+8 \hat{k}$ are perpendicular, then $\lambda$ is
[Kerala (Engg.) 2002]
Options:
A) - 14
B) 7
C) 14
D) 1/7
Show Answer
Answer:
Correct Answer: C
Solution:
- Let $ \mathbf{a}=3\mathbf{i}+\lambda \mathbf{j}+\mathbf{k} $ , $ \mathbf{b}=2\mathbf{i}-\mathbf{j}+8\mathbf{k} $ $ \because \mathbf{a}\bot \mathbf{b} $ , \ $ \mathbf{a} \mathbf{.} \mathbf{b}=0 $ $ (3\mathbf{i}+\lambda \mathbf{j}+\mathbf{k}) \mathbf{.} (2\mathbf{i}-\mathbf{j}+8\mathbf{k})=0 $ $ \mathbf{a}, \mathbf{b}, \mathbf{c} $
$ \Rightarrow \lambda =14. $
BETA
