Free Body Diagrams                                 Translational Mechanical Systems

Example1

Draw the free body diagram of the following system

 

Fig 2.12 a

 

Answer

Figure 2.12 b

 

Remarks:

  1. Only one free body diagram is needed (for the mass)
  2. There is a force ( the weight) that is ignored in the diagram. The reason is that the weight can be represented by an arrow pointing downward. Another force of equal magnitude is pointing upward. Both forces are perpendicular to the direction of motion and have no effect on it and therefore they areignored.