Equilibrium of a smooth cylinder resting on its curved (convex) surface A smooth right circular cylinder lies on a horizontal plane on its convex curved surface. The state of equilibrium is: Choose the correct type of equilibrium (stable, unstable, or neutral).

Concept
Type of equilibrium depends on how the center of gravity (C.G.) height changes for small displacements.

• Stable: small displacement raises C.G.; system tends to return.
• Unstable: small displacement lowers C.G.; system departs further.
• Neutral: small displacement does not change C.G. height.

Reasoning
A smooth cylinder rolling slightly on a horizontal plane about its line of contact keeps the C.G. at the same height; there is no change in potential energy for infinitesimal rolling.

Final Answer
neutral