Pick the correct statement from the following:
Try it first: pick an option, then read the explanation.
Correct answer: D. All options are correct
Asked in SSC JE 02/03/2017 (Evening)
Detailed Explanation
Load, shear and moment are linked by dV/dx = w and dM/dx = V. So the SFD is one degree higher than the load diagram, and the BMD one degree higher than the SFD.
Why “All options are correct” Is Correct
A UDL is degree 0, so the SF is linear (degree 1) and the BM is a parabola (degree 2). A linearly varying load is degree 1, so the SF is a parabola (degree 2). All three statements are true — option (d). (The book's option (b) printed “bulk modulus curve”; it means the bending moment curve.)
| Load on a segment | Shape of SFD | Shape of BMD |
|---|---|---|
| No load | Constant (horizontal line) | Linear (inclined straight line) |
| Point load | Sudden step equal to the load | Kink (change of slope) |
| UDL | Linear (1st degree) | Quadratic parabola (2nd degree) |
| Uniformly varying (triangular) load | Quadratic parabola | Cubic parabola (3rd degree) |
| Applied couple | No change | Sudden jump equal to the couple |
Why the Other Options Are Wrong
- A. For a uniformly distributed load, the shear force varies linearly: True, but (b) and (c) are also true.
- B. For a uniformly distributed load, the bending moment curve is a parabola: True, but (a) and (c) are also true.
- C. For a load varying linearly, the shear force curve is a parabola: True, but (a) and (b) are also true.
Key Point
Degree of BMD = degree of SFD + 1 = degree of load + 2.
Key Concepts for Students
- No load ⇒ constant SF, linear BM.
- Where SF changes sign, BM is maximum or minimum.
- Where BM changes sign is the point of contraflexure.
Practice more: this is question 31 in Bending Moment and Shear Force MCQs – Part 3. Try the whole set and check every answer instantly.