Question

If the bending of the beam is concave upwards then the bending moment developed is called __________ moment.

(a) Positive

(b) Negative

(c) Rotational

(d) Collinear

The question was posed to me in exam.

My doubt stems from Internal Forces Developed in Structural Members in chapter Internal Forces of Engineering Mechanics

Answer 1

Correct choice is (a) Positive

For explanation I would say: If the bending moment is giving concave bending upward to the body of the beam then the moment are said to be positive. That is if the bending moment is making the beam to develop in the forces that tend to bend the beam concave upward then it is considered to be positive. This is the basic sign convection that is being used to make the calculations easy.