The Algorithm

  1. Follow the first two steps in Newton's 2nd law
  2. Draw a normal axis (up/down, left/right)
  3. draw each force that is external to the system. If possible try to scale the forces appropriately.
  4. Label each force with its type of force (eq gravity, normal, friction), what object the force is acting on, and what object is causing the force.
  5. Determine if axis should be rotated.
  6. If the axis is rotated, draw the rotated axis along with the standard axis.
  7. identify and label all important angles on the free body diagram itself.
  8. Double check that you have all of the external forces. The number of force you should have should be equal to all of the objects that cross the system boundary plus the number of the objects that create friction with the system plus all of the non-contact forces.

Other resources

Fundamentals of FBDs (15min)

 

Here is a 4 step process to setup FBDs