Equilibrium is established when the sum of the forces acting on a body is zero. It can be classified as static or dynamic.
Static equilibrium: When the object is at rest;
Dynamic balance: When the body is in uniform rectilinear motion.
In stable equilibrium, when the body makes a small displacement in relation to its equilibrium position when released, it returns to the initial position.
When the equilibrium is unstable, by removing the object from its equilibrium position, it tends to move further away from it when dropped.
In indifferent equilibrium, when the object is moved, it remains in equilibrium in a new position.