Question

A pendulum is suspended from a point $A$ and is given a small initial velocity so that it starts oscillating. What will be the axis of rotation for this oscillating pendulum?

• A. A line passing through $A$ on the plane of oscillation.
• B. A line passing through the bob of the pendulum, perpendicular to the plane of oscillation.
• C. A line along the rod of the pendulum n the plane of oscillation.
• D. A line passing through $A$, perpendicular to the plane of oscillation.

Answer 1

The correct option is D A line passing through $A$, perpendicular to the plane of oscillation.

If we consider the pendulum as one system, then the pendulum oscillates about the point of suspension i.e. $A$.
All the particles of the system should be at a constant distance from the axis throughout its motion and the axis has to be in contact with the system. Hence the axis cannot be parallel to the plane of oscillation.