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When a mass is rotating in a plane about a fixed point, its angular momentum is directed along:
A
the tangent to the orbit
B
a line perpendicular to the plane of rotation
C
the line making an angle of $45^\circ$ to the plane of rotation
D
the radius
Detailed Solution
$\vec L = \vec r\times\vec p$
$\vec r$ and $\vec p$ both lie in the plane of rotation, and a cross product is perpendicular to both vectors.
So the angular momentum is directed along a line perpendicular to the plane of rotation.
$\vec r$ and $\vec p$ both lie in the plane of rotation, and a cross product is perpendicular to both vectors.
So the angular momentum is directed along a line perpendicular to the plane of rotation.