Question

Which of following is not considered as the true condition for the three members to be zero force members?

(a) Any two of the three members must be collinear

(b) There must be no external forces acting

(c) They should be joined by a joint

(d) Any two of the three members must be perpendicular

I had been asked this question in unit test.

This is a very interesting question from Zero Force Member in chapter Structural Analysis of Engineering Mechanics

Answer 1

Correct answer is (d) Any two of the three members must be perpendicular

To explain: The three members to be having a zero member must have any two of the three members collinear. There must be no external forces acting on the section or the joint which is being selected. And obviously all the members must be attached.