APSC JE 2025: Structural Mechanics & Hydraulics MCQs
Topics Covered
- Structural Mechanics: Stress and Strain
- Structural Mechanics: Beams and Bending
- Structural Mechanics: Trusses and Frames
- Hydraulics: Fluid Properties and Flow
- Hydraulics: Open Channel Flow and Pipes
1. What is the unit of stress in the SI system?
Answer: N/m²
Explanation: Stress is defined as force per unit area, and in the SI system, force is measured in Newtons (N) and area in square meters (m²). Thus, the unit of stress is N/m², also known as Pascal (Pa).
Explanation: Stress is defined as force per unit area, and in the SI system, force is measured in Newtons (N) and area in square meters (m²). Thus, the unit of stress is N/m², also known as Pascal (Pa).
2. A material has a Young's modulus of 200 GPa. If the stress is 100 MPa, what is the strain?
Answer: 0.0005
Explanation: Young's modulus (E) = Stress / Strain. Given E = 200 GPa = 200 × 10⁹ Pa, Stress = 100 MPa = 100 × 10⁶ Pa. Strain = Stress / E = (100 × 10⁶) / (200 × 10⁹) = 0.0005.
Explanation: Young's modulus (E) = Stress / Strain. Given E = 200 GPa = 200 × 10⁹ Pa, Stress = 100 MPa = 100 × 10⁶ Pa. Strain = Stress / E = (100 × 10⁶) / (200 × 10⁹) = 0.0005.
3. What is Poisson’s ratio?
Answer: Ratio of lateral strain to axial strain
Explanation: Poisson’s ratio is defined as the negative ratio of transverse (lateral) strain to axial strain in a material under uniaxial loading.
Explanation: Poisson’s ratio is defined as the negative ratio of transverse (lateral) strain to axial strain in a material under uniaxial loading.
4. A bar of length 2 m is subjected to a tensile force of 50 kN. If the cross-sectional area is 100 mm², what is the stress?
Answer: 500 MPa
Explanation: Stress = Force / Area. Force = 50 kN = 50 × 10³ N, Area = 100 mm² = 100 × 10⁻⁶ m². Stress = (50 × 10³) / (100 × 10⁻⁶) = 500 × 10⁶ Pa = 500 MPa.
Explanation: Stress = Force / Area. Force = 50 kN = 50 × 10³ N, Area = 100 mm² = 100 × 10⁻⁶ m². Stress = (50 × 10³) / (100 × 10⁻⁶) = 500 × 10⁶ Pa = 500 MPa.
5. Which of the following represents Hooke’s law?
Answer: Stress ∝ Strain
Explanation: Hooke’s law states that within the elastic limit, stress is directly proportional to strain, i.e., Stress = E × Strain, where E is Young’s modulus.
Explanation: Hooke’s law states that within the elastic limit, stress is directly proportional to strain, i.e., Stress = E × Strain, where E is Young’s modulus.
6. The volumetric strain in a material is related to:
Answer: Bulk modulus
Explanation: Volumetric strain is the change in volume per unit volume and is related to the bulk modulus, which measures a material’s resistance to uniform compression.
Explanation: Volumetric strain is the change in volume per unit volume and is related to the bulk modulus, which measures a material’s resistance to uniform compression.
7. The maximum shear stress in a beam occurs at:
Answer: Neutral axis
Explanation: For a beam in bending, the maximum shear stress occurs at the neutral axis, where the shear force is distributed across the smallest effective area.
Explanation: For a beam in bending, the maximum shear stress occurs at the neutral axis, where the shear force is distributed across the smallest effective area.
8. The bending moment equation for a simply supported beam with a point load at the center is:
Answer: WL/4
Explanation: For a simply supported beam with a point load W at the center, the maximum bending moment occurs at the center and is given by M = WL/4, where L is the span length.
Explanation: For a simply supported beam with a point load W at the center, the maximum bending moment occurs at the center and is given by M = WL/4, where L is the span length.
9. What is the section modulus of a rectangular beam of width b and depth d?
Answer: bd²/6
Explanation: The section modulus (Z) for a rectangular section is given by Z = I/y_max, where I = bd³/12 and y_max = d/2. Thus, Z = (bd³/12) / (d/2) = bd²/6.
Explanation: The section modulus (Z) for a rectangular section is given by Z = I/y_max, where I = bd³/12 and y_max = d/2. Thus, Z = (bd³/12) / (d/2) = bd²/6.
10. The deflection of a simply supported beam with a uniformly distributed load is maximum at:
Answer: Mid-span
Explanation: For a simply supported beam with a uniformly distributed load, the maximum deflection occurs at the mid-span due to symmetry and load distribution.
Explanation: For a simply supported beam with a uniformly distributed load, the maximum deflection occurs at the mid-span due to symmetry and load distribution.
11. The shear force diagram for a cantilever beam with a point load at the free end is:
Answer: Rectangular
Explanation: For a cantilever beam with a point load at the free end, the shear force is constant along the length, resulting in a rectangular shear force diagram.
Explanation: For a cantilever beam with a point load at the free end, the shear force is constant along the length, resulting in a rectangular shear force diagram.
12. The formula for maximum bending stress in a beam is:
Answer: My/I
Explanation: The bending stress in a beam is given by σ = My/I, where M is the bending moment, y is the distance from the neutral axis, and I is the moment of inertia.
Explanation: The bending stress in a beam is given by σ = My/I, where M is the bending moment, y is the distance from the neutral axis, and I is the moment of inertia.
13. A truss is considered statically determinate if:
Answer: m + r = 2j
Explanation: For a truss to be statically determinate, the number of members (m) plus the number of reactions (r) must equal twice the number of joints (2j).
Explanation: For a truss to be statically determinate, the number of members (m) plus the number of reactions (r) must equal twice the number of joints (2j).
14. In a truss, a zero-force member is identified when:
Answer: Two non-collinear members meet at a joint with no external load
Explanation: In a truss, if two non-collinear members meet at a joint with no external load or support, the third member at that joint carries no force, making it a zero-force member.
Explanation: In a truss, if two non-collinear members meet at a joint with no external load or support, the third member at that joint carries no force, making it a zero-force member.
15. The method of joints is used to determine:
Answer: Forces in truss members
Explanation: The method of joints involves analyzing the equilibrium of each joint in a truss to determine the forces in the members connected to that joint.
Explanation: The method of joints involves analyzing the equilibrium of each joint in a truss to determine the forces in the members connected to that joint.
16. A frame is different from a truss because:
Answer: Frames can resist bending moments
Explanation: Unlike trusses, which have pin joints and members that carry only axial forces, frames have rigid joints and can resist bending moments and shear forces.
Explanation: Unlike trusses, which have pin joints and members that carry only axial forces, frames have rigid joints and can resist bending moments and shear forces.
17. The degree of indeterminacy for a plane truss is given by:
Answer: m + r - 2j
Explanation: The degree of indeterminacy for a plane truss is calculated as m + r - 2j, where m is the number of members, r is the number of reactions, and j is the number of joints.
Explanation: The degree of indeterminacy for a plane truss is calculated as m + r - 2j, where m is the number of members, r is the number of reactions, and j is the number of joints.
18. In the method of sections, what is analyzed?
Answer: A cut section of the truss
Explanation: The method of sections involves cutting the truss through a section and analyzing the equilibrium of the cut portion to find forces in specific members.
Explanation: The method of sections involves cutting the truss through a section and analyzing the equilibrium of the cut portion to find forces in specific members.
19. The specific gravity of a fluid is defined as:
Answer: Density of fluid / Density of water
Explanation: Specific gravity is the ratio of the density of a fluid to the density of water at a standard temperature (usually 4°C).
Explanation: Specific gravity is the ratio of the density of a fluid to the density of water at a standard temperature (usually 4°C).
20. Viscosity of a fluid is a measure of its:
Answer: Resistance to shear deformation
Explanation: Viscosity is a measure of a fluid’s resistance to shear or flow, indicating how easily it deforms under shear stress.
Explanation: Viscosity is a measure of a fluid’s resistance to shear or flow, indicating how easily it deforms under shear stress.
21. Bernoulli’s equation is based on the conservation of:
Answer: Energy
Explanation: Bernoulli’s equation represents the conservation of mechanical energy per unit volume for an ideal fluid, balancing pressure, kinetic, and potential energies.
Explanation: Bernoulli’s equation represents the conservation of mechanical energy per unit volume for an ideal fluid, balancing pressure, kinetic, and potential energies.
22. The Reynolds number indicates:
Answer: Type of flow (laminar or turbulent)
Explanation: The Reynolds number (Re) is a dimensionless quantity that determines whether flow is laminar (Re < 2000) or turbulent (Re > 4000) in a pipe.
Explanation: The Reynolds number (Re) is a dimensionless quantity that determines whether flow is laminar (Re < 2000) or turbulent (Re > 4000) in a pipe.
23. The pressure at a depth h in a static fluid is given by:
Answer: ρgh
Explanation: The pressure at a depth h in a static fluid is P = ρgh, where ρ is the fluid density, g is the acceleration due to gravity, and h is the depth.
Explanation: The pressure at a depth h in a static fluid is P = ρgh, where ρ is the fluid density, g is the acceleration due to gravity, and h is the depth.
24. Surface tension is caused by:
Answer: Cohesive forces between molecules
Explanation: Surface tension arises due to the cohesive forces between the molecules of a liquid, causing the surface to act like a stretched membrane.
Explanation: Surface tension arises due to the cohesive forces between the molecules of a liquid, causing the surface to act like a stretched membrane.
25. Manning’s formula is used to calculate:
Answer: Velocity in open channel flow
Explanation: Manning’s formula, V = (1/n)R^(2/3)S^(1/2), is used to calculate the velocity of flow in an open channel, where n is the roughness coefficient, R is the hydraulic radius, and S is the slope.
Explanation: Manning’s formula, V = (1/n)R^(2/3)S^(1/2), is used to calculate the velocity of flow in an open channel, where n is the roughness coefficient, R is the hydraulic radius, and S is the slope.
26. The hydraulic radius of a channel is defined as:
Answer: Cross-sectional area / Wetted perimeter
Explanation: The hydraulic radius (R) is defined as the ratio of the cross-sectional area of flow to the wetted perimeter of the channel.
Explanation: The hydraulic radius (R) is defined as the ratio of the cross-sectional area of flow to the wetted perimeter of the channel.
27. Darcy-Weisbach equation is used to calculate:
Answer: Head loss in pipes
Explanation: The Darcy-Weisbach equation, h_f = f(L/D)(V²/2g), is used to calculate the head loss due to friction in pipes, where f is the friction factor, L is the pipe length, D is the diameter, V is the velocity, and g is the acceleration due to gravity.
Explanation: The Darcy-Weisbach equation, h_f = f(L/D)(V²/2g), is used to calculate the head loss due to friction in pipes, where f is the friction factor, L is the pipe length, D is the diameter, V is the velocity, and g is the acceleration due to gravity.
28. In open channel flow, critical depth occurs when:
Answer: Froude number = 1
Explanation: The critical depth in open channel flow occurs when the Froude number (Fr = V/√(gD)) equals 1, indicating a transition between subcritical and supercritical flow.
Explanation: The critical depth in open channel flow occurs when the Froude number (Fr = V/√(gD)) equals 1, indicating a transition between subcritical and supercritical flow.
29. The friction factor in the Darcy-Weisbach equation depends on:
Answer: Reynolds number and pipe roughness
Explanation: The friction factor (f) in the Darcy-Weisbach equation is determined using the Reynolds number (indicating flow regime) and the relative roughness of the pipe (ε/D).
Explanation: The friction factor (f) in the Darcy-Weisbach equation is determined using the Reynolds number (indicating flow regime) and the relative roughness of the pipe (ε/D).
30. The Chezy’s formula for open channel flow is given by:
Answer: V = C√(RS)
Explanation: Chezy’s formula for velocity in open channel flow is V = C√(RS), where C is Chezy’s coefficient, R is the hydraulic radius, and S is the slope of the energy grade line.
Explanation: Chezy’s formula for velocity in open channel flow is V = C√(RS), where C is Chezy’s coefficient, R is the hydraulic radius, and S is the slope of the energy grade line.