Question

The cross product of two vectors gives zero when the vectors enclose an angle of

• A. ${90}^o$
• B. ${180}^o$
• C. ${45}^o$
• D. ${120}^o$

Answer 1

The correct option is B ${180}^o$

We know that,

$|\overrightarrow{A}\times \overrightarrow{B}|=|\overrightarrow{A}||\overrightarrow{B}|\sin \theta$

If $|\overrightarrow{A}|$ and $|\overrightarrow{B}|$ are non zero.

Then,

$\overrightarrow{A}\times \overrightarrow{B}=0$ only if $\sin \theta =0$

$\sin \left({90}^o\right)=1$, $\sin \left({180}^o\right)=0$, $\sin \left({45}^o\right)=\frac{1}{\sqrt{2}}$

and $\sin \left({120}^o\right)=\frac{\sqrt{3}}{2}$. So,

option-B is correct.