Question

A body is uniformly rotating about an axis fixed in an inertial frame of reference. Let $\underset{A}{\to }$ be a unit vector along the axis of rotation and $\underset{B}{\to }$ be the unit vector along the resultant force on a particle P of the body away from the axis. The value of $\underset{A}{\to }.\underset{B}{\to }$ is
(a) 1
(b) −1
(c) 0
(d) none of these.

Answer 1

(c) 0

The unit vector along the axis of rotation and the unit vector along the resultant force on the particle are perpendicular to each other in a uniform rotation.
Therefore, we have:
$\overrightarrow{A}.\overrightarrow{B}=0$