6.6. Free Body Diagrams#
When evaluating force systems, it is helpful to create a free body diagram.
A free body diagram is a tool used to solve engineering mechanics problems. As the name suggests, the purpose of the diagram is to “free” the body from all other objects and surfaces around it so that it can be studied in isolation. We also draw any forces or moments acting on the body, including those forces and moments exerted by the surrounding bodies and surfaces that we removed.
Tip
A free body diagram includes the coordinate system of reference and all external forces acting on a free body.
How to Draw Free Body Diagrams#
Identify the body you wish to isolate and make a simple drawing of it.
Draw the appropriate force vectors at all location of supports, connections, and contact with other bodies.
Be sure to include a force vector for the weight of the body, unless gravitational force is to be neglected in the analysis.
Label all forces.
Draw a coordinate system on or near the free-body to establish directions of the forces.