What is the definition of equilibrium in the context of statics?

In the context of statics, equilibrium is defined as a state in which all forces and moments acting on a body are balanced. This means that the vector sum of all forces acting on the body equals zero, and similarly, the sum of all moments (or torques) about any point is also zero. When these conditions are satisfied, the body remains at rest or continues to move at a constant velocity, indicating that it is in a state of equilibrium.

This concept is fundamental in engineering mechanics as it allows for the analysis and design of structures and components under various loading conditions. Understanding equilibrium is essential for determining support reactions, internal forces, and overall stability of structures.

The other options do not accurately capture the comprehensive definition of equilibrium. For instance, a condition where forces cause a body to accelerate describes a dynamic situation, which is the opposite of equilibrium. The statement regarding a situation where no rotation occurs in a rigid body only addresses a specific aspect of statics but does not encompass the balance of forces, while stating that only external loads act on a structure neglects the importance of internal forces and moments in achieving equilibrium. Thus, the correct definition incorporates the idea of balance among all forces and moments acting upon the body.