The value of ' λ ' for which the two vectors a=5 i+λ j+k and b=i-2 j+k are perpendicular to each other is

Correct answer: (C) 3. Hints : For a ⊥ b a · b=0 i.e., 5-2 λ+1=0 λ=3

Q147 / 160 · WBJEE 2010 · Physics

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

Hints : For $\vec{a} \perp \vec{b}$ $\begin{aligned} & \vec{a} \cdot \vec{b}=0 \\ & \text { i.e., } 5-2 \lambda+1=0 \\ & \lambda=3 \end{aligned}$

Hence, the correct answer is option: 'C'.