4.8 Materials

• Materials can be classified into four main types
• Strength is the ability of a material to withstand an applied force
• Match the concept with its description:

  Stress ↔️ Force applied per unit area

  Strain ↔️ Deformation relative to original size
• Hooke's Law is valid beyond the elastic limit.

  False
• Strain is a dimensionless quantity.
• Why is understanding stress and strain important in engineering?

  Designing structures that withstand loads
• What does Young's Modulus represent in Hooke's Law?

  Stiffness of the material
• What is the strain in a steel wire with a Young's modulus of 200 GPa subjected to a stress of 400 MPa?

  0.002
• What type of force results in stretching of a material?

  Tensile
• Arrange the types of materials in order from strongest to most flexible:

  1️⃣ Composites

  2️⃣ Metals

  3️⃣ Ceramics

  4️⃣ Polymers
• Elastic materials can store energy when deformed.
• Stress is the force applied per unit area
• Strain is a dimensionless quantity.


  True
• What is the formula for stress?

  Stress = Force / Area
• Metals are crystalline solids with high electrical conductivity.

  True
• Elasticity allows a material to return to its original shape after stress.


  True
• The formula for strain is Change in Length / Original Length
• What are examples of metals?

  Iron, copper, aluminum
• What is the definition of plasticity in materials science?

  Permanent deformation without breaking
• Stress is defined as the force applied per unit area.


  True
• Stress can be tensile or compressive.


  True
• Match the term with its definition:

  Stress ↔️ Force applied per unit area

  Strain ↔️ Deformation relative to original size

  Units of Stress ↔️ Pascals (Pa)

  Units of Strain ↔️ Dimensionless
• The formula for Hooke's Law is σ = E × ε
• What are the three primary types of forces acting on materials?

  Tensile, Compressive, Shear
• Yield strength marks the transition from elastic to plastic deformation.
• Match the material type with its example:

  Metals ↔️ Copper

  Ceramics ↔️ Glass

  Polymers ↔️ Plastic

  Composites ↔️ Carbon Fiber
• What is the stress in a steel rod with an area of 0.01 m² subjected to a force of 50,000 N?

  5,000,000 Pa
• What are the units of stress?

  Pascals (Pa)
• What does Hooke's Law describe about the relationship between stress and strain?

  Proportionality up to elastic limit
• What is the formula for strain?

  Strain = Change in Length / Original Length
• Young's modulus (E) is a constant of proportionality representing stiffness
• How are tensile, compressive, and shear forces distinguished?

  Direction and effects
• What is the yield strength of a material?

  Stress at permanent deformation
• Fracture is the separation of a material into two or more parts due to excessive stress
• Match the material type with its key properties:

  Metals ↔️ High strength, electrical conductivity

  Ceramics ↔️ High hardness, heat resistance

  Polymers ↔️ Lightweight, flexible, corrosion-resistant

  Composites ↔️ Tailored strength-to-weight ratio
• What are examples of polymers?

  Plastics, rubber, nylon
• What is the key characteristic of plasticity?

  Permanent deformation
• What does Hooke's Law describe?

  Stress is proportional to strain
• Strong materials can withstand applied forces without breaking or deforming
• Plastic materials can be molded into new shapes