Q. A particle of mass $m$ is projected with a velocity $v$ making an angle of $45{^\circ}$ with the horizontal. The magnitude of angular momentum of projectile about the point of projection when the particle is at its maximum height $h$ is

A) Zero
B) $\frac{mvh}{\sqrt{2}}$
C) $\frac{mvh^{2}}{\sqrt{2}}$
D) None of these
Explanation

(b) The angular momentum of a particle is given by
$\overrightarrow{\mathbf{L}} = \overrightarrow{\mathbf{r}} \times m\overrightarrow{\mathbf{v}}$
$L = mvr\sin\theta$
[image:4_image108.emf]
From figure,
$L = rm(v\cos{45{^\circ}})\sin\theta$
$= \frac{mv}{\sqrt{2}}(r\sin\theta)$
$= \frac{mvh}{\sqrt{2}}\ \left( \because\ \sin{\theta = \frac{h}{r}} \right)$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

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