Question

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

• A. the axis of rotation
• B. line at an angle of ${45}^{\circ }$ to the axis of rotation
• C. the radius
• D. the tangent to the orbit

Answer 1

The correct option is A the axis of rotation

Angular momentum $\overrightarrow{L}=\overrightarrow{r}\times m\overrightarrow{v}$
As $\overrightarrow{r}$ directs towards point of rotation inwards and $\overrightarrow{v}$ acts tangentially thus their cross product is along the direction perpendicular to both, i.e. in the direction of axis of rotation.