Equilibrium (Mechanics)

Key Stage 5

Equilibrium is the state of an object when the net force and net moment acting on it are zero.

In static equilibrium, an object is at rest with no net force or moment acting on it.
In dynamic equilibrium, an object moves with constant velocity with no net force or moment acting on it.
Conditions for equilibrium include ∑𝐹=0 (no net force) and ∑𝜏=0 (no net moment).
Equilibrium is used to calculate unknown variables and predict physical outcomes of given situations (At what angle slope will an object tip over, what is the tension in the wires holding up a weight).
Stability of equilibrium can be classified as stable, unstable, or neutral.