1.3 Mechanical Properties of Materials

• Properties of materials: ductility, malleability, elasticity, brittleness, strength, hardness, stiffness
• Law of elasticity (Hooke's Law)
• Stress, strain and modulus of elasticity
• Industrial applications of the properties of materials

• explain the mechanical properties of materials
• demonstrate the mechanical properties of materials
• determine the tensile stress and strain using mathematical formulae
• describe applications of mechanical properties of materials
• appreciate the importance of knowledge on mechanical properties of materials in day-to-day life

“Why does a string snap easily compared to a spring?”

“Why does a glass bottle break when the water in it freezes?”

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1. How materials behave when you push them
   40 min · 2 practice tasks · quiz
   Seven properties that decide what a material can be used for, and why glass and copper fail so differently.
2. Hooke's law, stress and strain
   40 min · 2 practice tasks · quiz
   The straight-line rule that holds until it does not, and how engineers compare materials fairly.
3. Elastic and plastic behaviour
   40 min · 1 practice tasks · quiz
   When a material springs back, and when it keeps a permanent set after the load is gone.
4. Investigating Hooke's law
   40 min · 1 practice tasks · quiz
   Load a spring in equal steps, plot force against extension, and read k from the gradient.
5. Stress, strain and Young's modulus
   40 min · 1 practice tasks · quiz
   Tensile, compressive and shear stress, and using Young's modulus as the stiffness of a material.
6. Strength of materials
   40 min · 1 practice tasks · quiz
   Strength is the stress a material can take before it fails, and it depends on how you load it.
7. Hardness and how we test it
   40 min · 1 practice tasks · quiz
   Hardness is resistance to scratching or denting, tested by which material marks the other.
8. Brittleness and ductility
   40 min · 1 practice tasks · quiz
   How a material fails: a sudden snap with no warning, or stretching and a neck first.
9. Toughness and impact
   40 min · 1 practice tasks · quiz
   Toughness is the energy a material can absorb before it fractures, not how hard or strong it is.
10. Choosing materials in Kenya
    40 min · 1 practice tasks · quiz
    Timber, steel, concrete and rubber: match each property to a job on a Kenyan site or vehicle.