Theory of Structures

81. The radius of gyration of a rectangular section (depth D, width B) from a centroidal axis parallel to the width is

1. D/2
2. D/√3
3. D/2√3
4. D/4√3

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82. The stiffness of the close coil helical spring is

1. d⁴N/8D³n
2. d⁴N/4D³n
3. 4D³N/d⁴n
4. 8D3³/d⁴n

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83. For beams breadth is constant,

1. Depth d ∝ M
2. Depth d ∝ √M
3. Depth d ∝3 √M
4. Depth d ∝ 1/M

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84. At any point of a beam, the section modulus may be obtained by dividing the moment of inertia of the section by

1. Depth of the section
2. Depth of the neutral axis
3. Maximum tensile stress at the section
4. Maximum compressive stress at the section

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85. A road of uniform cross-section A and length L is deformed by δ, when subjected to a normal force P. The Young's Modulus E of the material, is

1. E = δ/A. L
2. E = δ/P. L
3. E = P. L/A. δ
4. E = P. A/L. δ

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86. If E, N, K and 1/m are modulus of elasticity, modulus of rigidity. Bulk modulus and Poisson ratio of the material, the following relationship holds good

1. E = 3K (1 - 2/m)
2. E = 2N (1 + 1/m)
3. (3/2)K (1 - 2/m) = N (1 + 1/m)
4. All the above

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87. The deflection of a uniform circular bar of diameter d and length 'l', which extends by an amount 'e' under a tensile pull 'W', when it carries the same load at its mid-span, is

1. el/2d
2. e²l/3d²
3. el²/3d²
4. e²l²/3d²

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88. The maximum magnitude of shear stress due to shear force F on a rectangular section of area A at the neutral axis, is

1. F/A
2. F/2A
3. 3F/2A
4. 2F/3A

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89. Stress may be defined as

1. Force per unit length
2. Force per unit volume
3. Force per unit area
4. None of these

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90. The forces in the members of simple trusses, may be analysed by

1. Graphical method
2. Method of joints
3. Method of sections
4. All the above

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