Agricultural/Bioengineering Strength of Materials 2

Question 1

A steel grain bin support column has a cross-sectional area of 0.005 m² and carries an axial compressive load of 50 kN. What is the compressive stress?

Accepted Answer

10 MPa

Answer

Stress = Force / Area = 50,000 N / 0.005 m² = 10 MPa.

Question 2

Which of the following materials has the highest modulus of elasticity (stiffness) and is commonly used in agricultural machinery frames?

Accepted Answer

Structural steel

Answer

Structural steel has a modulus of elasticity of approximately 200 GPa, far higher than the other options.

Question 3

A wooden irrigation flume beam spans 4 m and carries a uniformly distributed load. If the maximum bending moment is 8 kN·m and the section modulus is 0.002 m³, what is the bending stress?

Accepted Answer

4 MPa

Answer

Bending stress = M / S = 8,000 N·m / 0.002 m³ = 4 MPa.

Question 4

In a thin-walled cylindrical silo storing grain, which stress is approximately twice the longitudinal (axial) stress when internal pressure acts?

Accepted Answer

Hoop (circumferential) stress

Answer

For a thin-walled pressure vessel, hoop stress = pd/2t is twice the longitudinal stress = pd/4t.

Question 5

A tractor drawbar pin experiences a shear force of 20 kN across two shear planes (double shear). If the pin diameter is 20 mm, what is the average shear stress?

Accepted Answer

15.9 MPa

Answer

Double shear area = 2 × π(0.01)² = 6.283×10⁻⁴ m²; τ = 20,000 / 6.283×10⁻⁴ ≈ 31.8 MPa — wait, single shear area = π(0.01)² = 3.14×10⁻⁴ m², double shear τ = 20,000 / (2 × 3.14×10⁻⁴) ≈ 31.8 MPa.

Agricultural/Bioengineering Practice Test

Agricultural/Bioengineering Practice Test

Agricultural/Bioengineering Strength of Materials 2