'The change in slope between two points on a straight member under flexure is equal to the area of the M/EI diagram between those two points' is a theorem of which method?
Try it first: pick an option, then read the explanation.
Correct answer: D. Moment area method
Asked in SSC JE 28/10/2020 (Evening)
Detailed Explanation
The moment area method rests on two theorems by Otto Mohr. The statement in the question is the first of them.
Why “Moment area method” Is Correct
Change in slope = area of the M/EI diagram is Mohr's first theorem of the moment area method. The second theorem gives deflection from the moment of that area.
Why the Other Options Are Wrong
- A. Castigliano's method: Castigliano's method uses partial derivatives of strain energy.
- B. Strain energy method: The strain energy method equates external work to stored energy.
- C. Unit load method: The unit load method uses ∫Mm dx/EI with a virtual unit load.
Key Point
Area of M/EI diagram ⇒ change in slope (moment area method, Mohr I).
Key Concepts for Students
- Mohr II: deflection = moment of the M/EI area.
- Moment area works best when one tangent is known (cantilever or symmetric beam).
- Conjugate beam method is a restatement of these theorems.
Practice more: this is question 23 in Slope and Deflection MCQs – Part 2. Try the whole set and check every answer instantly.