Question

When a mass is rotating in a plane about a fixed point, its angular momentum is directed along

• A. The radius
• B. Tangent to the orbit
• C. Line perpendicular to the plane of motion
• D. None of these

Answer 1

The correct option is C Line perpendicular to the plane of motion

Angular Momentum $L=I\overrightarrow{\omega }$

$\overrightarrow{\omega }=\overrightarrow{r}\times \overrightarrow{v}$

By rules of cross product, $\overrightarrow{\omega }$ is $\perp$ to $\overrightarrow{r}$ & $\overrightarrow{v}$

$\overrightarrow{r}$ & $\overrightarrow{v}$ are in plane of rotation.

$\Rightarrow$ Angular Momentum is perpendicular to plane of motion.