Three-Hinged Arches MCQ with answer and solution

Concept

A cable is assumed to be perfectly flexible (no bending resistance) and inextensible. So it carries only axial tension.

Step-by-step solution

1. In cable analysis, the bending moment at every point of the cable is zero. 2. This is true only if the cable is perfectly flexible. 3. The cable is also assumed to be inextensible, so its length does not change under load. 4. So the answer is 'Perfectly flexible', which is option A.

Explanation

A cable cannot resist bending, so it is taken as perfectly flexible and it carries only tension. Its stretching under load is ignored, so it is also taken as inextensible.

Why the other options are wrong

B is wrong because an inflexible cable would resist bending. C is wrong because the cable is assumed inextensible. D is wrong because of the word 'extensible'.

Shortcut

Cable means flexible and inextensible, pure tension, zero bending moment.

Common mistake

Choosing option D because it contains 'flexible', and not noticing that 'extensible' is wrong.