Rigid-Body Motion & Classical Mechanics

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Abstractions about rotation, translation, forces, coordinates, and dynamics of rigid or linked bodies. They include angular displacement and Euler angles, generalized coordinates, diagrams and free-body models, inertia devices, contact forces, levitation, and many-body motion.

18 abstractions in this family — domain-specific abstractions that sit near one another in structural-signature space (k-means over structural-signature embeddings). Each is shown with its short description.

• Angular displacement — The directed change in rotational position between two orientations about a specified axis or within a declared orientation representation.
• Center of percussion — The point on a pivoted rigid body where a perpendicular impulse produces no instantaneous reaction impulse at the pivot.
• Centrode — The locus traced by the instantaneous center of rotation of a rigid body undergoing planar motion.
• Classical mechanics — A physical theory describing macroscopic motion through forces, mass, momentum, energy, and deterministic equations without quantum effects and usually without relativistic corrections.
• Euler angles — Three ordered rotation angles that parameterize a three-dimensional orientation relative to a reference frame under a declared axis sequence and active or passive convention.
• Falling cat problem — The mechanics problem of how a deformable body can reorient while total angular momentum remains zero by cycling its internal shape through noncommuting configurations.
• Free body diagram — A diagram isolating a body and displaying the external forces and moments acting on it.
• Generalized coordinates — A minimal set of independent parameters that uniquely specifies a mechanical system’s configuration subject to its constraints.
• Ground reaction force — The contact-force vector exerted by a supporting surface on a body, including normal and frictional components and measured as the reaction to the body's loading of the ground.
• Inerter (mechanical networks) — A two-terminal mechanical element whose equal and opposite terminal force is proportional to relative acceleration, serving as the mechanical analogue of an electrical capacitor.
• Inertia wheel pendulum — An underactuated control-system model consisting of a pendulum with a motor-driven reaction wheel whose internal torque regulates the pendulum angle.
• Kinematic diagram — A schematic representation of a mechanism that preserves links, joints and their connectivity while suppressing most physical shape, scale and manufacturing detail.
• Levitation (physics) — The stable suspension of an object against gravity without direct mechanical contact, produced by an upward force together with restoring forces that resist displacement.
• N-body problem — The problem of determining the coupled motion of multiple bodies interacting through mutual forces, classically Newtonian gravitation.
• Pedobarography — Measurement and analysis of plantar pressure fields at the foot-support interface over stance or gait, using spatially resolved platforms or in-shoe sensors.
• Popliteal height — The seated vertical distance from the supporting floor beneath the foot to the underside of the thigh at the knee, used in ergonomic fit and anthropometry.
• Rigid rotor — An idealized rotating-body model in which mass distribution and internal distances remain fixed while orientation changes.
• Rotation number — An invariant measuring the average angular displacement of an orientation-preserving circle homeomorphism under repeated iteration, taken modulo one.