Q. A particle of mass $m = 5\ $units is moving with a uniform speed $v\ = 3\ \sqrt{2}\ $m in the $XOY$ plane along the line $Y\ = \ X + \ 4$. The magnitude of the angular momentum about origin is
A) Zero
B) 60 unit
C) 7.5 unit
D) $40\sqrt{2}\ unit$
Explanation
(b) Angular momentum about origin
$\left| \mathbf{L} \right| = |\mathbf{r} \times m\mathbf{v}|$
$= (4\cos{45{^\circ}) \times (5) \times 3\sqrt{2}}$
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$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ = \frac{a}{\sqrt{2}} \times 5 \times 3\sqrt{2}$
$\left| \mathbf{L} \right| = 60\ unit$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.