Question

The improper constraining leading to instability occurs when ___________________

(a) The reactive forces are parallel

(b) The reactive forces are perpendicular

(c) The reactive forces are equal

(d) The reactive forces are rotational

The question was posed to me in unit test.

Question is from Constraints and Statical Determinacy topic in chapter Equilibrium of a Rigid Body of Engineering Mechanics

Answer 1

The correct choice is (a) The reactive forces are parallel

For explanation I would say: If the forces are parallel (the reactive forces) then this creates an instability. That is this is also a type of improper constraining which is resulting in instability of the structure. Thus reactive forces are parallel are resulting in the instability of the body.