Static and dynamic balance
Equilibrium is established when the sum of the forces acting on a body is zero. It can be classified as static or dynamic.
A body is in equilibrium when the sum of all forces acting on it is zero, that is, equal to zero. According to Newton’s First Law, when the resultant of the forces acting on a body is zero, the body remains in its state of rest or in uniform rectilinear motion. Therefore, an object in equilibrium can be at rest or in uniform rectilinear motion. Balance can be classified as:
Static equilibrium: When the object is at rest;
Dynamic balance: When the body is in uniform rectilinear motion.
Furthermore, it can be of three types: stable, unstable or indifferent.
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.