Question

$0.4\hat{i}+0.8\hat{j}+c\hat{k}$ represents a unit vector when $c$ is

• A. $-0.2$
• B. $\sqrt{0.2}$
• C. $\sqrt{0.8}$
• D. $0$

Answer 1

Answer: (B)

$\sqrt{0.2}$

$\sqrt{(0.4{)}^2+(0.8{)}^2+c^2}=1$
$\Rightarrow 0.16+0.64+c^2=1\Rightarrow c=\sqrt{0.2}$