Strength of Materials— Important Topics, Formulas & MCQs
Strength of Materials (SOM) is the backbone of Civil Engineering exams. It deals with how solid bodies deform and fail under loads — stress, strain, bending, shear, torsion and buckling. Almost every WBPSC AE, SSC JE and RRB JE paper draws 8–12 questions directly from SOM, and it underpins RCC, Steel and Structural Analysis as well.
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Important topics in Strength of Materials
Key concepts & formulas — Strength of Materials
Flexure formula
M/I = σ/y = E/R — relates bending moment, bending stress and radius of curvature. Section modulus Z = I/y.
Relation between E, G, K
E = 2G(1+μ) = 3K(1−2μ). A very frequently asked numerical.
Euler's buckling load
P = π²EI/Le². Effective length Le depends on end conditions (both fixed → L/2, both hinged → L, one fixed-one free → 2L).
Torsion equation
T/J = τ/r = Gθ/L for circular shafts. Polar moment J = πd⁴/32 (solid).
Typically the single highest-scoring subject (8–12 questions in WBPSC AE / SSC JE). High return on study time because the concepts repeat across RCC and Steel.
Master SFD/BMD and the flexure formula first — they unlock bending stress, deflection and design questions across multiple subjects.
Sample Strength of Materials MCQ
A simply supported beam of span L carries a central point load W. The maximum deflection is: