Question

If the dot product of the two vectors of non-zero magnitude is zero then:

• A. they must be parallel.
• B. they must be antiparallel.
• C. they must be perpendicular.
• D. the angle between them depends on their magnitudes

Answer 1

The correct option is C they must be perpendicular.

Dot product of two vectors $a$ and $b$ is $\overrightarrow{a}.\overrightarrow{b}=abcos\theta$ where $\theta$ is the angle between them.
$ab\cos \theta =0\Rightarrow cos\theta =0\Rightarrow \theta ={90}^{\circ }$