Holonomic constraint

Summary

A holonomic constraint on a mechanical system is an equation between the positions of its parts and possibly the time. Rigid rods, inextensible strings and surfaces on which a particle must stay give such constraints. Each independent holonomic constraint removes one coordinate, so a system with holonomic constraints can be described by fewer, independent coordinates. Constraints that only restrict velocities and cannot be reduced to position equations are called nonholonomic.