Strength of Materials UNIT- II

Stress is defined as:

• Force per volume

• Area per force

• Force per unit area

• Length per force

Answer explanation

Stress is defined as force applied per unit area. This means that the correct choice is 'Force per unit area', as it accurately describes how stress is measured in physics.

Strain is defined as:

• Load per area

• Change in dimension / Original dimension

• Area ◊ Load

• Mass per unit force

Answer explanation

Strain measures how much a material deforms relative to its original size. It is calculated as the change in dimension divided by the original dimension, making 'Change in dimension / Original dimension' the correct definition.

Unit of stress is:

• N

• N/m≤ (Pa)

• N∑m

• kg/m≤

Answer explanation

The unit of stress is defined as force per unit area. In SI units, this is expressed as Newtons per square meter (N/m²), which is also known as Pascal (Pa). Therefore, the correct answer is N/m² (Pa).

Hooke’s Law is valid within the:

• Plastic region

• Elastic limit

• Ultimate point

• Breaking point

Answer explanation

Hooke’s Law states that the force exerted by a spring is proportional to its extension, but this is only true within the elastic limit. Beyond this point, materials may deform plastically and not return to their original shape.

The modulus of elasticity is also called:

• Bulk modulus

• Shear modulus

• Young’s modulus

• Yield modulus

Answer explanation

The modulus of elasticity refers specifically to Young's modulus, which measures the stiffness of a material. The other options, such as bulk modulus and shear modulus, describe different material properties.

Unit of Young’s modulus is:

• N

• m

• N/m≤ (Pa)

• N∑m

Answer explanation

Young's modulus measures the stiffness of a material and is defined as stress over strain. Its unit is Pascal (Pa), which is equivalent to N/m². Therefore, the correct answer is N/m² (Pa).

Which of these is a compressive force system?

• Pulling

• Pushing

• Twisting

• Shearing

Answer explanation

A compressive force system involves forces that push or compress an object. Among the options, 'Pushing' is the only action that applies compressive force, while pulling, twisting, and shearing involve tension or other types of forces.

Tensile force causes a material to:

• Elongate

• Shorten

• Twist

• Shear

Answer explanation

Tensile force pulls on a material, causing it to elongate or stretch. This is the primary effect of tensile forces, making 'Elongate' the correct answer.

Shear stress acts:

• Perpendicular to the surface

• Parallel to the surface

• On the edge

• In the center

Answer explanation

Shear stress acts parallel to the surface, causing layers of material to slide past each other. This is distinct from normal stress, which acts perpendicular to the surface.

Modulus of rigidity relates to:

• Bulk strain

• Shear strain

• Tensile strain

• Compressive strain

Answer explanation

Modulus of rigidity, also known as shear modulus, measures a material's response to shear strain. It quantifies how much a material deforms under shear stress, making 'shear strain' the correct choice.