A rigid body is placed on a horizontal table. When slightly disturbed, its centre of gravity moves horizontally without any rise or fall in its position. Which one of the following correctly describes the state of the body?

An object is in neutral equilibrium if, when slightly disturbed, its centre of gravity (CG) remains at the same vertical height. In this state, the body's potential energy remains constant because the CG moves horizontally without any rise or fall. Consequently, the body remains in its new position without any restoring or overturning forces acting upon it.

• Stable equilibrium: When disturbed, the CG rises, and the body tends to return to its original position.
• Unstable equilibrium: When disturbed, the CG falls, and the body moves further away from its original position.

A classic example of neutral equilibrium is a uniform sphere or cylinder resting on a flat horizontal table; as it rolls, the height of its CG remains constant relative to the surface.