In the figure I show a small segement of a larger truss leaving out completely how many members are attached to the joints labelled 1,3, and 4. All members connected to joint 2 are shown though.

The two features to look out for are :

  1. a joint with only three members attached (here the joint 2 ).
  2. two of the members are aligned (here member 12 and 23).
In such a case the third member (here member 24) is a zero-force member, that is F24=0.

The reason ? Well, look at the sum of the force on joint 2 in the direction perpendicular to the two aligned members 12 and 23.

Last revised: Aug 7, 1997
Zig Herzog