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

Options

A. the tangent to the orbit
B. a line perpendicular to the plane of rotation
C. the line making an angle of `45^@` to the plane of rotation
D. the radius

Answer

B

Explanation

(b) `vec L = vec r xx vec p`
By right-hand screw, rule, the direction of `vec L` is perpendicular to the plane containing `vec r & vec p`.
The mass is rotating in the plance about a fixed point thus this plane will contain `vec r & vec p` and the direction of `vec L` will be perpendicular to this plane.