Q. If $|\overrightarrow{\mathbf{a}} \times \overrightarrow{\mathbf{b}}|^{2} + |\overrightarrow{\mathbf{a}} \bullet \overrightarrow{\mathbf{b}}|^{2} = 144\ and\ \left| \overrightarrow{\mathbf{a}} \right| = 4\ then\ |\overrightarrow{\mathbf{b}}|\$ is equal to

A) 12
B) 3
C) 8
D) 4
Explanation

(b)
Given, $|\overrightarrow{\mathbf{a}} \times \overrightarrow{\mathbf{b}}|^{2} + |\overrightarrow{\mathbf{a}} \bullet \overrightarrow{\mathbf{b}}|^{2} = 144$
$\Longrightarrow \left| \overrightarrow{\mathbf{a}} \right|^{2}{+ \left| \overrightarrow{\mathbf{b}} \right|}^{2}\left( \sin^{2}\theta + \cos^{2}\theta \right) = 144$
$\Longrightarrow 16\left| \overrightarrow{\mathbf{b}} \right|^{2} = 144$
$\Longrightarrow \left| \overrightarrow{\mathbf{b}} \right| = 3$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.

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