Concept:Unstable equilibrium means that a small displacement makes the cone fall farther away from its original position, causing its centre of gravity to move downward.
Explanation:A cone in unstable equilibrium, for example when balanced on its apex, has its centre of gravity at a raised position.
The base of support is very small, so the equilibrium is easily disturbed.
When the cone is slightly displaced, it topples over and the height of its centre of gravity decreases.
Gravitational potential energy is given by
P.E.=mgh.
Since the height
h decreases, the potential energy also decreases.
Therefore, a cone in unstable equilibrium has a decreased potential energy after displacement.
Answer:A. decreased