Question

The vector sum of two forces P and Q is minimum when the angle between them is

• A. $\frac{\pi }{4}$
• B. $\frac{\pi }{3}$
• C. $\frac{\pi }{2}$
• D. $\pi$

Answer 1

The correct option is D $\pi$

$|\overrightarrow{P}+\overrightarrow{Q}|=\sqrt{P^2+Q^2+2PQ\cos \theta }$
Vector sum is minimum when $\cos \theta$ is minimum i.e. $\theta =\pi$.