Q. The resultant of two vectors of magnitudes $2A$ and $\sqrt{2}A\ $acting at an angle $\theta$ is $\sqrt{10}A$. The correct value of $\theta$ is
A) 30${^\circ}$
B) 45${^\circ}$
C) 60${^\circ}$
D) 90${^\circ}$
Explanation
(b) $10A^{2} = 4A^{2} + 2A^{2} + 2 \times 2A \times \sqrt{2}A \times cos\theta$
or $4A^{2}$=4$\sqrt{2}A\ cos\theta$
or $cos\theta = \frac{1}{\sqrt{2}} \Rightarrow \theta = 45{^\circ}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.