Question

Given that $0.2\hat{i}+0.6\hat{j}+a\hat{k}$ is a unit vector. What is the value of a?

• A. $\sqrt{0.3}$
• B. $\sqrt{0.4}$
• C. $\sqrt{0.6}$
• D. $\sqrt{0.8}$

Answer 1

The correct option is C

$\sqrt{0.6}$

Here, $(0.2{)}^2+(0.6{)}^2+a^2=1$
$\Rightarrow a^2=1-0.04-0.36=0.6$
$\Rightarrow a=\sqrt{0.6}$
Hence, the correct choice is (c).