Free-Body Diagram

This is EXTREMELY IMPORTANT for problem-solving.

A sketch which represents a body isolated from its surroundings and shows all forces and moments exerted on the body. It is an “Equilibrium Tool”


  1. Identify particle/body of interest
  2. Sketch particle/body free of constraints
  3. Apply External forces and moments
  4. (if needed) Replace constraints with force reactions and moment reactions
  5. (if needed) Add dimensions