Question

Consider the following statements regarding shearing force and bending moment :

1. Point of contra flexure is the point where bending moment changes its sign.

2. Shear force is the rate of change of bending moment.

3. For bending moment to be maximum or minimum, shear force should change its sign.

4. Rate of change of loading is equal to shear force.

Which of the above statements are correct?

1. 2 and 3 only
2. 1 and 4 only
3. 1, 2 and 4 only
4. 1, 2 and 3 only

Answer 1

Correct Answer - Option 4 : 1, 2 and 3 only

Explanation:

a) In a bending beam, a point of contra flexure is a location where the bending moment is zero (changes its sign). In a bending moment diagram, it is the point at which the bending moment curve intersects with the zero lines.

• At the point of contra flexure, the bending moment is zero.

​b) The rate of change of bending moment at any section is equal to the shear force at that section.

• \(\frac{{dM}}{{dx}} = F \Rightarrow dM = Fdx \Rightarrow M = \smallint Fdx\)

c) The rate of change of shear force at any section is equal to load intensity at that section.

• \(\frac{{dF}}{{dx}} = \omega \Rightarrow dF = \omega dx \Rightarrow F = \smallint \omega dx\)

d) For bending moment to be maximum or minimum, shear force should change its sign.