Question

We are given a vector $\overrightarrow{OA}=3\hat{i}+4\hat{j}+5\hat{k}$. Then the magnitude of component of the vector lying perpendicular to the $y-z$ plane is

• A. None of the above
• B. $5$
• C. $4$
• D. $3$

Answer 1

The correct option is D $3$

We know that $x,y,z$ axes are perpendicular to each other.
$\Rightarrow \hat{i},\hat{j},\hat{k}$ are perpendicular to each other.
So, the direction perpendicular to $y-z$ plane is $x$ i.e. $\hat{i}$.
Hence, the magnitude of component of the vector lying perpendicular to the $y-z$ plane is $3$.

Hence, option $\left(\text{A}\right)$ is the right choice.