By Will Weston and Bill Weigle

 Stability pertains to the movement of an object’s center of gravity (also referred to as CG).  Relates to the state of equilibrium that an object is in.

 Various types of equilibriums go hand-in- hand with stability.  An unstable equilibrium describes an object balanced in a position that any displacement lowers its center of gravity.  A stable equilibrium is found in an object balanced in such a way that any displacement raises its center of gravity.  A neutral equilibrium is found in an object where the center of gravity is neither raised or lowered by displacement.

 A cone placed on its point will have a lower CG with any movement. Therefore, a cone in this position is in unstable equilibrium.  A cone placed on its base will have an increased CG with any movement. A cone in this position is in stable equilibrium.  A cone placed on its side will not experience any change in CG when it is moved. Therefore, a cone in this position is in neutral equilibrium. An example of unstable, stable, and neutral equilibrium. 14/mechanics/Statics/text/Stability_/index.html

 Stability and center of gravity can be applied to many real-world concepts.  When a large portion of a building’s structure is below ground level, the building has a lower center of gravity. ◦ This is a crucial aspect to the structure of tall, narrow structures (like the Space Needle in Seattle). ◦ If such a structure were to shift, its center of gravity would rise (thus preventing the structure from falling).

 #11. Distinguish between unstable, stable, and neutral equilibrium. ◦ An object that is balanced so that any displacement lowers its center of gravity is considered to be in unstable equilibrium. When an object is balanced so that any displacement raises its center of gravity, it is considered to be in stable equilibrium. An object is considered to be in neutral equilibrium when its displacement does not directly affect its center of gravity.