One of the conditions of a force system in equilibrium is:

In a force system in equilibrium, one of the fundamental conditions is that the vector sum of all forces acting on the object must be zero. This condition supports the notion that the forces acting on the left side of a system must balance those acting on the right side.

If we consider a system in equilibrium, the forces acting in opposing directions should cancel each other out completely. Therefore, the sum of the forces directed to the left must equal the sum of the forces directed to the right for the object to remain in a state of rest or uniform motion according to Newton's First Law of Motion. This balance is crucial; if there were any net force, the object would accelerate in the direction of that net force, violating the equilibrium condition.

Understanding this principle is critical in fields related to engineering and physics as it applies to various static systems and structures, ensuring stability and safety in design and construction.