Question

Two vectors $\overset{\rightarrow}{A}$ and $\overset{\rightarrow}{B}$ are at right angles to each other, when

• A. (a) $\overset{\rightarrow}{A} + \overset{\rightarrow}{B} = 0$
• A. (b) $\overset{\rightarrow}{A} - \overset{\rightarrow}{B} = 0$
• A. (c) $\overset{\rightarrow}{A} \times \overset{\rightarrow}{B} = 0$
• A. (d) $\overset{\rightarrow}{A}.\overset{\rightarrow}{B} = 0$

Answer 1

(d)

Sol. $\overrightarrow{A}.\overrightarrow{B} = |\overrightarrow{A}|.|\overrightarrow{B}|.\cos\theta = \overrightarrow{A}.\overrightarrow{B}.\cos 90{^\circ} = 0$