Grade 10 physics – Mechanical Properties of Materials Quiz

Strain is the ratio of extension (change in length) to the original length and is dimensionless. Stress is force per unit area, Young's modulus relates stress to strain, and tensile strength is the maximum stress a material can withstand.

Hooke's law states that within the elastic limit, stress is proportional to strain (σ = Eε). Newton's second law concerns force and acceleration, Archimedes is about buoyancy, and Pascal's law concerns pressure in fluids.

Toughness measures the energy a material can absorb before breaking (area under stress-strain curve). Brittle materials break with little plastic deformation, malleability refers to forming under compressive stress, and hardness measures resistance to surface indentation.

The elastic limit or yield point marks the end of elastic behaviour; beyond it deformation is permanent. The proportional limit is where linearity ends, ultimate tensile is maximum stress, and fracture is where the material breaks.

Young's modulus is a measure of stiffness: higher E means less strain for a given stress (stiffer). It does not directly indicate brittleness or density.

Ultimate tensile strength (UTS) is the maximum engineering stress on the stress-strain curve before necking. Yield strength is where plastic deformation begins, elastic limit is similar to yield, and shear modulus relates shear stress to shear strain.

Glass is brittle: it fractures with very little plastic deformation. Ductile materials (like mild steel) show significant plastic deformation; rubber is highly elastic; viscoelastic behaviour is typical of some polymers.

A tensile test stretches a specimen while measuring load and extension, producing a stress–strain curve from which Young's modulus, yield point and tensile strength can be obtained. Hardness and impact tests give different information.

Hardness measures resistance to surface indentation or scratching. Toughness is energy absorption before fracture, elasticity is reversible deformation, and ductility is the ability to undergo plastic deformation (e.g., to be drawn into wire).

For springs in series, reciprocals add: 1/keff = 1/k1 + 1/k2, so keff = (k1*k2)/(k1 + k2). For parallel springs keff = k1 + k2.

Within the elastic limit, deformation is reversible: removing the load lets the rod return to its original length. Permanent change occurs only if the elastic limit is exceeded.

Young's modulus is a material property dependent on bonding, structure, temperature and defects. It is independent of the applied force magnitude as long as the material remains in the elastic region.

Ductility is measured by how much a material can plastically deform before fracture — often expressed as percent elongation or reduction in cross-sectional area at fracture.

Ductile steels typically resist fatigue and can absorb cyclic stresses without sudden fracture. Brittle ceramics, glass, and cast iron are prone to crack growth and failure under repeated loading.

After yielding and as plastic deformation continues, a ductile specimen develops a local reduction in cross-sectional area called necking, which leads to eventual fracture.

Shear stress acts parallel to the area causing layers to slide past each other (scissors action). Stretching is tensile stress, compressing is compressive stress, and heating is thermal.

Young's modulus determines stiffness and how much a beam will deflect under load. Electrical conductivity, chemical reactivity and colour are unrelated to bending stiffness.

Safety factors give margin against unknowns such as higher loads, imperfections, or environmental effects, ensuring structures remain safe. They are not intended to make structures heavier for its own sake.

Copper is ductile and easily drawn into wires. Glass, granite and brittle ceramics fracture easily and are not suitable for wire drawing.

The area under the entire stress–strain curve up to fracture equals the energy per unit volume a material can absorb before breaking — its toughness. Modulus is the initial slope, yield strength is a point on the curve, density is unrelated.

Cold working introduces dislocations that increase hardness and reduce ductility. Annealing softens and restores ductility. Melting/recasting can change properties depending on processing; polishing affects surface finish only.

Brittle fractures usually occur suddenly with little plastic deformation and often produce a flat, crystalline fracture surface. Ductile fractures show significant plastic deformation and necking before failure.

Stress = force/area = 100 N / (2×10^-6 m^2) = 50,000,000 Pa = 5×10^7 Pa.

Increasing temperature usually makes metals more ductile and reduces stiffness (Young's modulus decreases). Brittleness and density typically do not increase with temperature.

Shear modulus G relates shear stress to shear strain (τ = G·γ). The ratio of tensile stress to tensile strain is Young's modulus; area under curve is toughness; maximum load before fracture relates to tensile strength.

For a linear spring, the elastic potential energy stored is the work done to stretch it: (1/2) k x^2. kx is the force, not the energy; energy is not zero.

Stress is defined as the force acting on a material divided by the area over which the force acts (σ = F/A). This gives a measure of how concentrated the force is in the material.

Strain measures relative deformation: how much a material stretches or compresses compared to its original length (ε = ΔL / L0). It has no units.

Hooke's Law states that, within the elastic limit, the extension (or deformation) is proportional to the applied force (F = kx for springs).

Young's modulus (E) measures stiffness: E = stress/strain while the material behaves elastically (i.e., it returns to its original shape when the load is removed).

The elastic limit is the highest stress that produces only reversible (elastic) deformation; beyond it permanent (plastic) deformation occurs.

The yield point marks the transition from elastic behavior to plastic deformation; beyond this, the material will not return fully to its original shape.

UTS is the maximum point on the engineering stress–strain curve, representing the highest stress a material can sustain before it starts to fail.

Ductile materials (like mild steel) stretch or deform a lot before breaking, while brittle materials (like glass) break with little plastic deformation.

Toughness is the amount of energy a material can absorb before fracturing; it combines strength and ductility (area under the stress–strain curve).

Hardness quantifies how resistant a material surface is to indentation, scratching, or abrasion (e.g., measured by Mohs or Rockwell tests).

Stress = Force / Area. For the same force, reducing the area increases stress, so a thinner rod feels more stress.

For similar springs, stiffness k is inversely proportional to length; a longer spring is less stiff and so extends more under the same force (x = F/k).

Stress is the tensile force divided by the cross-sectional area: σ = F/A, measured in pascals (N/m²).

Engineering strain is change in length divided by original length. It is a dimensionless ratio: ε = ΔL/L0.

The proportional limit is the end of the region where stress and strain are proportional; Hooke’s law (linear relation) holds up to this point.

The energy stored in a linear spring is (1/2)kx^2, where k is the spring constant and x is the extension (or compression).

Young's modulus is stress divided by strain. Since strain is dimensionless and stress has units N/m^2, Young's modulus is measured in pascals (Pa).

Concrete is strong under compression but weak under tension; steel provides tensile strength, so reinforced concrete beams combine both strengths for safer structures.

Annealing softens metals, relieving internal stresses and making them more ductile and easier to shape, though often reducing hardness.

Creep is gradual plastic deformation occurring over long times under constant stress, especially at elevated temperatures (important in boilers, turbines).

Fatigue occurs when a material breaks after many cycles of loading and unloading, often at stresses much lower than the UTS, common in bridges and vehicle parts.

Shear stress acts tangentially to a surface and tries to make adjacent layers slide past each other, as in scissors cutting or bolts under shear load.

Bulk modulus K relates pressure change to relative volume change: K = −V (ΔP/ΔV). It indicates how hard it is to compress a material.

Poisson's ratio ν = −(lateral strain)/(axial strain). When a material is stretched, it usually becomes thinner laterally; the negative sign makes ν positive.

If expansion is prevented by fixed ends, the rod cannot lengthen and thermal expansion produces compressive stresses (thermal stress).