Question

Which of the following is/are necessary and sufficient condition(s) for pure rotation?

• A. All particles of the body will move in concentric circles.
• B. All particles move in a circle contained in parallel planes.
• C. Centre of all the particles of the body lie on a same straight line called the Axis of rotation.
• D. Axis of rotation is always perpendicular to the planes of the circles

Answer 1

Answer: (B), (C), (D)

Axis of rotation is always perpendicular to the planes of the circles

The axis can be anywhere inside or outside. But to state that the motion of that body is pure rotation it should quality mentioned criteria-

1. All particles move in a circle contained in parallel planes.

2. Centres of all the particles of the body lie on a same straight line, also called the Axis of rotation.

3. Axis of rotation is always perpendicular to the planes of the circles.