Mechanical Properties of Materials | OCR A-Level Physics B (Advancing Physics) (H557)
Mechanical Properties of Materials
- 125 questions
- 8 subtopics
- The physics content, examined on all three papers
- Component 01, Component 02 and Component 03
Mechanical Properties of Materials is examined in all three written papers — the specification states that Components 01, 02 and 03 each assess content from across all the teaching modules, so nothing is confined to one paper.
It covers elastic and plastic deformation and fracture, Hooke's law and force-extension graphs, elastic strain energy, stress, strain and the Young modulus, measuring the Young modulus and fracture stress of a metal, Describing and comparing materials, metals, ceramics and polymers and direct evidence for the size and spacing of particles.
Sample questions from Mechanical Properties of Materials
Answer each one closed book first, then open the answer.
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Elastic and plastic deformation and fracture
Define fracture stress.
Show the answer
Fracture stress is the stress at which a material breaks, calculated from the greatest force it carried and its original cross-sectional area. -
Hooke's law and force-extension graphs
A spring of stiffness 25 N m⁻¹ is stretched by 80 mm. Calculate the force applied.
Show the answer
F = 25 × 0.080 = 2.0 N. -
Elastic strain energy
A spring of stiffness 80 N m⁻¹ is stretched by 50 mm. Calculate the energy stored.
Show the answer
E = ½ × 80 × 0.050² = 0.10 J. -
Stress, strain and the Young modulus
State the unit of the Young modulus and a typical order of magnitude for a metal.
Show the answer
It is measured in pascals, and for a metal it is of the order of 10¹¹ Pa. -
Measuring the Young modulus and fracture stress of a metal
State what is plotted and how the Young modulus is obtained from the graph.
Show the answer
Plot stress against strain and take the gradient of the straight portion, or plot force against extension and multiply the gradient by original length divided by cross-sectional area. -
Describing and comparing materials
Define ductile.
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A ductile material can be drawn out into a wire, undergoing large plastic deformation without breaking. -
Metals, ceramics and polymers
Explain why work hardening makes a metal harder but more brittle.
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Deformation multiplies and tangles the dislocations so that they obstruct one another, which resists further slip but leaves the metal little capacity for plastic deformation. -
Direct evidence for the size and spacing of particles
Describe Rayleigh's oil drop experiment.
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A drop of oil of known volume is placed on a clean water surface lightly dusted with powder, and the drop spreads into a circular patch whose diameter is measured.
The 8 subtopics
One subtopic is one session. Work down the list.
| Subtopic | What it covers | Questions |
|---|---|---|
| Elastic and plastic deformation and fracture | Recall questions on elastic and plastic deformation, the elastic limit, yield stress, fracture and fracture stress, brittle and ductile fracture, necking, elastic and plastic behaviour in terms of atoms and dislocations, tension and compression, tough, hard and strong materials, and the behaviour of a rubber band. | 16 |
| Hooke's law and force-extension graphs | Recall questions on Hooke's law and F = kx, stiffness from a force–extension graph, the limit of proportionality, springs joined end to end and side by side, rubber band loading loops and the energy they represent, polythene strips, measuring a spring's force–extension characteristic, unloading, plotting extension, and safety precautions and pointers. | 16 |
| Elastic strain energy | Recall questions on elastic strain energy, the area under a force–extension graph, E = ½kx² and why it is ½Fx rather than Fx, calculations for springs, bungee cords and catapults, doubling the extension, materials that do not obey Hooke's law, energy beyond the elastic limit, and why a stretched rubber band warms. | 14 |
| Stress, strain and the Young modulus | Recall questions on tensile stress and strain and their units, the Young modulus and its typical size for metals, why it beats stiffness for comparing materials, calculating stress, strain, Young modulus, extension and fracture stress, the stress–strain graph of a ductile metal, and why stress–strain graphs compare wires of different thickness. | 17 |
| Measuring the Young modulus and fracture stress of a metal | Recall questions on the wire arrangement and reference wire, measuring diameter at several points, what is plotted, safety and clamping, readings taken while unloading, and finding fracture stress. | 15 |
| Describing and comparing materials | Recall questions on the meanings of stiff, strong, tough, brittle, ductile and hard, telling stiffness from strength, why glass fracture stress varies, and properties wanted in concrete or cutting tools. | 16 |
| Metals, ceramics and polymers | Recall questions on the structure of metals, dislocations and slip, ductility, hardening a metal with foreign atoms, work hardening and annealing, the structure of ceramics and why they are brittle and stronger in compression, polymer chains and their large extensions, stiffening rubber, cross-links, brittle cold polymers, and metal grains. | 16 |
| Direct evidence for the size and spacing of particles | Recall questions on scanning tunnelling microscope images and how the microscope works, why the tunnelling current is so sensitive to the gap, the atomic spacing it shows, Rayleigh's oil drop experiment and its single-layer assumption, calculating film thickness, measuring the drop and the patch, its errors and upper estimate, and why particle size matters for materials. | 15 |
How the guide is worked
Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.
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Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
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Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
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Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.
Read the full method, the return schedule and the research behind it.
Nearby topics
OCR A-Level Physics B (Advancing Physics) Active Recall Guide
Every topic, not just this one. 2,455 questions with their answers.