Question

If $0.4\hat{i}+0.7\hat{j}+c\hat{k}$ is a unit vector, then the value of $c$ is:

• A. $\sqrt{0.67}$
• B. $\sqrt{0.12}$
• C. $\sqrt{1.44}$
• D. $\sqrt{0.35}$

Answer 1

The correct option is D $\sqrt{0.35}$

$\sqrt{{0.4}^2+{0.7}^2+c^2}=1Thus,c^2=1-0.65=0.35,orc=\sqrt{0.35}$