Question

Let A be a unit vector along the axis of rotation of a purely rotating body and B be a unit vector along the velocity of a particle P of the body away from the axis. The values of A.B is -
(a) 1
(b) -1
(c) 0
(d) None of these.

Answer 1

Answer ⇒ Option (c). 0

Explanation ⇒ The unit vector A along the axis of the Rotation of the Purely rotating body will be Perpendicular to the Unit vector B along the Particle P of the body from its axis.

Mathematically, Angle between them = θ = 90°

Now,

A.B = |A| |B|Cos θ [A.B is the dot product.]

= |A| |B| Cos 90°

= |A| |B| 0

= 0

Hence, the correct answer is Option (c).

Hope it helps.