BCE Mechanics of Materials

Question 1

What is the SI unit of stress?

Accepted Answer

Pascal (Pa)

Answer

Newton (N)

Answer

Joule (J)

Answer

Watt (W)

Question 2

Hooke's Law states that stress is proportional to strain within the elastic limit. The constant of proportionality is called the:

Accepted Answer

Modulus of elasticity (Young's modulus)

Answer

Poisson's ratio

Answer

Shear modulus

Answer

Bulk modulus

Question 3

A steel rod with a cross-sectional area of 500 mm² is subjected to an axial tensile load of 100 kN. What is the tensile stress?

Accepted Answer

200 MPa

Answer

100 MPa

Answer

50 MPa

Answer

400 MPa

Question 4

Poisson's ratio (ν) is defined as the ratio of:

Accepted Answer

Lateral strain to longitudinal strain

Answer

Longitudinal strain to lateral strain

Answer

Shear stress to shear strain

Answer

Volumetric strain to linear strain

Question 5

Beyond the elastic limit of a material, what occurs when the load is removed?

Accepted Answer

Permanent (plastic) deformation remains

Answer

The material returns fully to its original dimensions

Answer

The material fractures immediately

Answer

Necking begins at the midpoint

Question 6

A steel bar (E = 200 GPa) of length 2 m and cross-sectional area 200 mm² carries an axial tensile load of 40 kN. What is the elongation?

Accepted Answer

2 mm

Answer

1 mm

Answer

0.5 mm

Answer

4 mm

Question 7

The factor of safety in structural design is defined as the ratio of:

Accepted Answer

Ultimate (failure) stress to allowable (working) stress

Answer

Working stress to ultimate stress

Answer

Yield stress to elastic limit

Answer

Elastic limit to working stress