Question

What is the direction of angular velocity for the second hand of a clock going from 0 to 30 seconds?
(A) Outward from the clock face
(B) Inward towards the clock face
(C) Upward
(D) Downward
(E) To the right

Answer 1

Hint:Since angular velocity is in rotational motion and a vector quantity the right hand rule tells its direction. Curl the fingers in the direction of rotation along the axis and the thumb indicates the direction of angular velocity

Complete step by step answer:
Angular velocity is a vector quantity having both magnitude and direction.
To find out the direction of angular velocity we need to use the right-hand rule. The direction of angular velocity is always perpendicular to the plane of rotation. According to this right-hand rule, the fingers curl in the direction of rotation and the thumb pointing is the direction of the angular velocity.


In this case the fingers are pointing at zero seconds and curl the fingers as it changes to 30 seconds along the axis of rotation now the thumb is pointing towards the clock which is the direction of angular velocity.

Hence, the direction of angular velocity is inwards towards the clock face and the correct option is B.

Note This right-hand rule is basically used to define the direction of the cross product of 2 vectors. It points in the direction which is perpendicular to both of these vectors. In this case angular velocity is defined as the cross product of the radius of the circle with the linear velocity of the particle. Its direction is also pointed mutually perpendicular to both of these vectors.