What term describes an object whose motion neither decays nor grows after a disturbance?

What term describes an object whose motion neither decays nor grows after a disturbance?

• A. Positive dynamic stability
• B. Neutral dynamic stability
• C. Negative dynamic stability
• D. Static stability

Answer: (B)

How a system behaves after a disturbance defines its dynamic stability class. If the motion dies away, the system is positively dynamically stable. If the motion grows without bound, it’s negatively dynamically stable (unstable). When the disturbance leaves the motion at a constant amplitude—neither decaying nor growing—the system is neutrally dynamically stable. This means there’s no damping to reduce the motion and no mechanism to amplify it, so the response persists at the same level, such as a steady oscillation or constant motion. Static stability, by contrast, focuses on whether a displaced position would be restored by restoring forces without considering how the motion evolves over time, so it doesn’t describe this ongoing behavior.

How a system behaves after a disturbance defines its dynamic stability class. If the motion dies away, the system is positively dynamically stable. If the motion grows without bound, it’s negatively dynamically stable (unstable). When the disturbance leaves the motion at a constant amplitude—neither decaying nor growing—the system is neutrally dynamically stable. This means there’s no damping to reduce the motion and no mechanism to amplify it, so the response persists at the same level, such as a steady oscillation or constant motion. Static stability, by contrast, focuses on whether a displaced position would be restored by restoring forces without considering how the motion evolves over time, so it doesn’t describe this ongoing behavior.