Maximum Bending Moment - Strength of Materials Questions and Answers

This set of Strength of Materials Multiple Choice Questions & Answers (MCQs) focuses on “Maximum Bending Moment”.

1. A cantilever beam subjected to point load at its free end, the maximum bending moment develops at the ________ of the beam.
a) Free end
b) Fixed end
c) Centre
d) Point of inflection
View Answer

Answer: b
Explanation: As the moment is the product of perpendicular distance and force. In cantilever beam, at its free end the moment will be zero as there is no distance, but at the fixed end the moment is maximum that is W×l.

2. Bending moment in a beam is maximum when the _________
a) Shear force is minimum
b) Shear force is maximum
c) Shear force is zero
d) Shear force is constant
View Answer

Answer: c
Explanation: The maximum bending moment occurs in a beam, when the shear force at that section is zero or changes the sign because at point of contra flexure the bending moment is zero.

3. Positive bending moment is known as _______
a) Hogging
b) Sagging
c) Ragging
d) Inflection
View Answer

Answer: a
Explanation: The positive bending moment in a section is considered because it causes convexity downwards. Such bending moment is called a sagging bending moment or positive bending moment.

4. A simply supported beam of span “x” meters carries a udl of “w” per unit length over the entire span, the maximum bending moment occurs at _____
a) At point of contra flexure
b) Centre
c) End supports
d) Anywhere on the beam
View Answer

Answer: b
Explanation: As we know that BM occurs at center. Because at supports the moment is obviously zero.
At the centre, maximum bending moment is wl²/8.

The maximum bending moment occurs at Centre simply supported beam of span “x” meters

5. The maximum BM is ______
a) 40 kNm
b) 50 kNm
c) 90 kNm
d) 75 kNm
View Answer

Answer: c
Explanation: Above diagram depicts cantilever beam subjected to point load at the free end. The maximum bending moment at A is W × I
= 30 × 3
= 90 kNm.

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6. Bending moment can be denoted by ____
a) K
b) M
c) N
d) F
View Answer

Answer: b
Explanation: Bending moment is the product of force and perpendicular distance. Units are kNm
It is denoted by “M”. Whereas SF is denoted by “F”.

7. Number of points of contra flexure for a double over hanging beam.
a) 3
b) 2
c) 4
d) Infinite
View Answer

Answer: b
Explanation: Point of contraflexure in a beam is a point at which bending moment changes its sign from positive to negative and vice versa. In the case of overhanging beam, there will be two points of contraflexure.

8. Maximum bending moment in a cantilever beam subjected to udl (w)over the entire span (l).
a) wl
b) wl³
c) wl²
d) w
View Answer

Answer: c
Explanation: In a cantilever beam the maximum bending moment occurs at the fixed end. Moment at the free end is 0 and maximum at the fixed end. Maximum shear force is w×l.

9. Determine the maximum bending moment for the below figure.

a) wl/2
b) wl/3
c) wl/4
d) wl
View Answer

Answer: c
Explanation: First of all, let’s assume the length between end supports be ”l” the maximum bending moment in a simply supported beam with point load at its centre is wl/4. We know that in simply supported beam the maximum bending moment occurs at the centre only.

10. What is the variation in the BM, if the simply supported beam carries a point load at the centre.
a) Triangular
b) Rectangular
c) Trapezoidal
d) Other quadrilateral
View Answer

Answer: a
Explanation: For simply supported beam with point load at the centre, the maximum bending moment will be at the centre i.e. wl/4. The variation in bending moment is triangular.