Free Body Diagram Technique

Application of Newton’s laws to solve problems in mechanics becomes easier by use of the free body diagram technique. A diagram which shows all the forces acting on a body in a given situation is called a free body diagram (FBD).

The procedure to draw a free body diagram is:

  1. Draw a simple, neat diagram of the system as per the given description.
  2. Isolate the object of interest. This object will be called the Free Body now.
  3. Consider all external forces acting on the free body and mark them by arrows touching the free body with their line of action clearly represented.
  4. Now apply Newton’s second law ΣF = ma

For obtaining a complete solution, you must have as many independent equations as the number of unknowns.