Rigid body equilibrium exists when a rigid body under the influence of a force system is in a stable equilibrium.
What is a rigid body?Edit
It is a fictional object that is a useful approximation. The rigid body cannot be deformed, which means it cannot be squished or broken. Mathematically, we would say that every point on the rigid body will retain their distance and position relative to one another not matter the force. If we were to subject it to two forces approaching infinity, it would not be harmed.
How are they useful?Edit
Rigid bodies are useful approximations because we will often be faced with materials that are not under enormous amounts of strain- the force is very small relative to the material's modulus of elasticity. We will go over how to see whether or not a rigid body is in equilibrium in two dimensions, and then be able to generalize that to three dimensions.