Introduction to Units and Measurements

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Questions and Answers

Which property characterizes the ability of solids to return to their original shape after the removal of an external force?

Ductility

Plasticity

Strength

Elasticity (correct)

What is the correct definition of stress in the context of mechanical properties?

Total deformation experienced by a material

Restoring force per unit area acting on the material (correct)

Force required to change the shape of a material

Force per unit volume experienced by a body

Which of the following correctly differentiates liquids from gases?

Liquids have definite volume but no definite shape (correct)

Liquids have definite shape and easily compressible

Gases have defined volume and high density

Gases have strong intermolecular forces and low density

What is the SI unit for measuring stress?

Pascal (Pa) Signup and view all the answers

Which characteristic of solids allows them to be drawn into thin wires?

Ductility Signup and view all the answers

What is the effect of applying an external force to a material regarding its strain?

It induces a change in length relative to its original length Signup and view all the answers

What is the definition of Young's modulus?

The ratio of longitudinal stress to longitudinal strain. Signup and view all the answers

Which of the following statements is true about fluids compared to solids?

Fluids have low density and can adapt their shape easily Signup and view all the answers

Which of the following statements regarding tensile strain is accurate?

It measures the change in length per unit length. Signup and view all the answers

What distinguishes plasticity from elasticity in materials?

Plasticity results in permanent deformation, while elasticity does not Signup and view all the answers

In the context of stresses, which type is related to the deformation due to internal forces acting parallel to the surface?

Shear stress Signup and view all the answers

Which of the following best describes hydraulic stress?

The force exerted by fluid pressure on a surface. Signup and view all the answers

What effect does a higher Young's modulus have on a material?

More stress is required for a given change in length. Signup and view all the answers

Which type of strain measures the change in volume relative to the original volume of a material?

Volume strain Signup and view all the answers

What is the unit of Young's modulus?

Pascal (Pa) Signup and view all the answers

Which modulus is defined as the ratio of shear stress to shear strain?

Shear modulus Signup and view all the answers

What best describes the relationship between stress and strain within the elastic limit?

Stress and strain are proportional to each other. Signup and view all the answers

Which type of modulus corresponds to the ratio of tensile stress to tensile strain?

Young's modulus Signup and view all the answers

What happens to a material when it exceeds its elastic limit?

It becomes permanently deformed. Signup and view all the answers

In which type of stress does the force act perpendicular to the cross-section area?

Tensile stress Signup and view all the answers

Which formula represents the relationship between stress, strain, and modulus of elasticity?

Stress = Modulus × Strain Signup and view all the answers

Study Notes

Units and Measurements

Physical quantity: A measurable property describing a system's state.
Two types of quantities: Fundamental (basic physical attributes) and derived (combinations of fundamental quantities).
Measurement includes two components: a number and a unit (e.g., 50 m, 5 s, 10 kg).
Systems of units: CGS (centimeter, gram, second), FPS (foot, pound, second), MKS (meter, kilogram, second), and SI (International System of Units).

Phases of Matter

Matter consists of atoms and molecules; light is not considered matter.
Two main types of matter: Solids and Fluids.
Solids: Rigid, with a definite shape and size, high density, and strong intermolecular forces, making them incompressible.
Fluids:
- Liquids: Definite volume but no definite shape, low density, not easily compressible, and exhibit weak to moderate intermolecular forces.
- Gases: No definite shape or volume, very low density, easily compressible, and possess very weak intermolecular forces.

Mechanical Properties of Solids

Elasticity: Ability to regain original shape upon removal of external force; does not change mechanical properties.
Plasticity: Permanent deformation, where the material does not return to its original shape; often changes mechanical properties.
Ductility: Capability of being drawn into thin wires or sheets; linked to malleability.
Strength: Resistance to applied stress without failure.
Stress: Internal restoring force per unit area due to applied external force, calculated as Stress = Force (F) / Area (A), measured in Pascal (Pa).

Strain

Strain: Measure of deformation relative to an original length, indicating changes under stress.
Strain formula: ΔL / Lo, where ΔL is change in length and Lo is original length.
Strain is dimensionless—no units—and arises from stress.

Elasticity, Stress, and Strain

Stress and strain exhibit proportionality until reaching the elastic limit, beyond which the material deforms permanently.
Modulus of elasticity: Proportionality constant between stress and strain, defined as Stress = Modulus × Strain.
Three types of modulus:
- Young’s modulus (longitudinal),
- Shear modulus,
- Bulk modulus.

Types of Stress and Strain

Types of stress:
- Tensile stress: Stretching or compressive force along length.
- Shearing stress: Parallel force applied on a cross-section.
- Hydraulic stress: Force applied uniformly from all sides leading to volume changes.
Types of strain:
- Tensile strain: (ΔL/L),
- Shear strain: (Δx/L),
- Volume strain: (ΔV/V).

Young’s Modulus (Y)

Young’s modulus quantifies elasticity by relating longitudinal stress to longitudinal strain.
Formula: Y = (F/A) / (ΔL/L) = FL / AΔL.
Higher Young’s modulus indicates that more stress is needed for a small length change.
SI Unit is Newton per square meter (N/m²) or Pascal (Pa).

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Description

This quiz covers essential concepts of units and measurements in physical science. It includes fundamental and derived quantities, the role of measurement in describing physical properties, and different systems of units such as CGS, FPS, MKS, and SI. Test your knowledge on these foundational topics crucial for understanding the phases of matter.