A rigid body is in equilibrium when the forces and moments acting on it sum to zero — no net translation, no net rotation. It underpins most of structural and mechanical analysis.
Equilibrium questions turn up regularly in the statics section of the FE exam, usually asking you to find unknown reactions from a free-body diagram.
Video Tutorial
Identifying forces and writing the equilibrium equations
Equilibrium of Rigid Bodies Video Solution →
What the Tutorial Covers
How to identify every external force acting on a body, draw the free-body diagram, and apply the equilibrium equations to solve for unknowns.
Quick Review with Shorts
Our YouTube Shorts cover free-body diagrams and the equilibrium conditions in under a minute each.
Smart Quiz
The numbers change every attempt — practice the method, not the answer
How the Quiz Works
Instant feedback with a full explanation on every question. Get one wrong and the walkthrough shows you where the reasoning went off.
📝 INTERACTIVE PRACTICE QUIZ
Equilibrium of Rigid Bodies Quiz
Reaction forces and moment problems, with new values each attempt.
Worked Examples
One from practice, one from the real world
Practice Problem
A 6 m horizontal beam is pinned at A and supported by a roller at B, carrying a 500 N vertical load.
Summing moments about the pin gives the roller reaction; summing vertical forces then gives the pin reaction. Free-body diagram first, equations second.
Real-World Example
A traffic light hanging from a cantilever beam. Engineers account for the light’s weight, the horizontal and vertical components of cable tension, and the reactions at the pole — the same equilibrium equations, applied to hardware you drive past daily.
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