Wobbly Desk

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Hd.1: Object O on floor F can {\em wobble} between configurations C1 and C2 if C1 and C2 are both stable configurations; O can be moved from C1 to C2 with little effort; it requires substantially greater effort to move O to any other stable configuration. There is generally a single best path through configuration space taking the object from C1 to C2, which are its endpoint.

H.1: A flat rectangular desk with equal length vertical legs at its four corners on a flat floor has a unique stable position with all four legs touching the ground.
Statics, deterministic, prediction.

H.2: Let the legs of the table be labelled A,B,C,D in cyclic order. If A or C or both is shortened, or the length of B or D or both is lengthed, relative to H.1, then the table will wobble between a position where A,B,D touch the ground, and one where B,C,D touch the ground.
Dynamics, deterministic, prediction.

H.3: Let the legs of the table be labelled A,B,C,D in cyclic order. If a hole is gouged out of floor F underneath A or C or a bump is added to floor F underneast B or D, then the table will wobble between a position where A,B,D touch the ground, and one where B,C,D touch the ground.
Dynamics, deterministic, prediction.

H.4: If a desk with four legs wobbles between positions where it is supported by the legs, then it either wobbles between A,B,D and B,C,D or between A,B,C and A,C,D.
Dynamics, deterministic, prediction.

H.5: If a desk with four legs is wobbling between A,B,D and B,C,D, the wobble can be eliminated by bringing it to A,B,D, and inserting a wedge underneath C until the wedge is in contact with both the floor and leg C.
Dynamics, deterministic, plan.

H.6. Suppose a desk wobbles between A,B,D and B,C,D. If a sufficiently heavy weight is placed near A, then position B,C,D will become unstable, and the system will setttle to state A,B,D.
Dynamics, deterministic, prediction.

H.7. Suppose a desk wobbles between A,B,D and B,C,D. If a weight is placed on A's side of the line B-D, then position B,C,D tends to become unstable and the system will tend to setttle to state A,B,D. The greater the weight and the further from line B-D, the stronger this tendency. If the weight is sufficiently light or sufficiently close to the line, then the wobble is not affected; if it is sufficiently heavy and far from the line, then the wobble is definitely eliminated.
Dynamics, tendency, prediction.

Cause to wobble by angling floor

Eliminate wobble by bracing against wall.

Eliminate wobble by weighting corner.