Question

Let $\underset{A}{\to }$ be a unit vector along the axis of rotation of a purely rotating body and $\underset{B}{\to }$ be a unit vector along the velocity of 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

For a purely rotating body, the axis of rotation is always perpendicular to the velocity of the particle.
Therefore, we have:
$\overrightarrow{A}.\overrightarrow{B}=0$