Question

Two vector A and B have equal magnitudes. Then the vector A + B is perpendicular to

• A. $A \times B$
• B. A – B
• C. 3A – 3B
• D. All of these

Answer 1

Answer: (A)

$A \times B$

Answer 2

$\overrightarrow{A} \times \overrightarrow{B}$ is a vector perpendicular to plane $\overrightarrow{A} + \overrightarrow{B}$ and hence perpendicular to $\overrightarrow{A} + \overrightarrow{B}$.