Torsion, Cylinders and Trusses

JKSSB Junior Engineer (Civil) · Mechanics and Structural Analysis · 20 practice questions with answers and explanations: 12 Easy, 7 Medium, 1 Hard.

Sample questions

Sample Easy question 1

A zero-force member in a truss is found at a joint where:

  1. Three members meet with a load
  2. Two collinear members meet with a load
  3. Two non-collinear members meet and no external load acts
  4. A support is placed
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Answer: C. Both members carry no force, and they can be removed for the analysis.

Sample Easy question 2

A two-span continuous beam on three supports is statically indeterminate to the:

  1. Third degree
  2. It is determinate
  3. Second degree
  4. First degree
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Answer: D. It has three reactions against the two available equations of equilibrium (vertical loads).

Sample Easy question 3

Castigliano's theorem states that the deflection at the point of a load is:

  1. The square of the strain energy
  2. The slope times the span
  3. The integral of the bending moment
  4. The partial derivative of the strain energy with respect to that load
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Answer: D. δ = ∂U ÷ ∂P.

Sample Medium question 4

A plane pin-jointed truss with 8 joints is just stiff (perfect). The number of members is:

  1. 8
  2. 13
  3. 12
  4. 16
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Answer: B. m = 2j − 3 = 16 − 3 = 13. A truss with 14 members and 8 joints would be redundant by 1.

Sample Medium question 5

The torque that produces a shear stress of 50 N/mm² in a solid shaft of 60 mm diameter is about:

  1. 0.212 kN·m
  2. 4.24 kN·m
  3. 21.2 kN·m
  4. 2.12 kN·m
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Answer: D. T = τ × πd³ ÷ 16 = 50 × π × 60³ ÷ 16 = 2.12 × 10⁶ N·mm.

Sample Medium question 6

A plane pin-jointed truss has 7 joints. For it to be just stiff (perfect), the number of members is:

  1. 14
  2. 11
  3. 7
  4. 10
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Answer: B. m = 2j − 3 = 14 − 3 = 11.

Sample Hard question 7

A shaft of length 2 m, G = 80 GPa and J = 10⁶ mm⁴ carries a torque of 1 kN·m. The angle of twist is:

  1. 0.0025 rad
  2. 0.25 rad
  3. 0.05 rad
  4. 0.025 rad
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Answer: D. θ = T L ÷ (G J) = 10⁶ × 2,000 ÷ (80,000 × 10⁶) = 0.025 rad.

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