Elasticity Study Guide: NEB 11 Physics

Turn content into performance

How this study guide fits the concept chapter

The Elasticity concept guide explains stress, strain, moduli and material curves. This page schedules their practice. The CDC Grade 11 Physics page remains the Nepal scope checkpoint.

The OpenStax institutional treatment separates tensile, bulk and shear deformation. Your study evidence should do the same; formula recall without identifying deformation is fragile.

Start with evidence

A 20-minute Elasticity diagnostic

1. Define stress and strain with SI units.
2. Explain stiffness versus strength.
3. Convert 2 mm² to m².
4. Predict wire extension when radius doubles.
5. Choose a modulus for length, volume and shape change.
6. Label linear, elastic, plastic and fracture regions on a sketch.
7. Explain why Hooke’s law cannot be extrapolated indefinitely.

Three models, one pattern

The stress–strain–modulus map

For every model, write: applied stress, corresponding strain, modulus and validity condition. This repeated pattern reduces disconnected memorisation while preserving the physical differences.

Six focused sessions

A practical Elasticity learning sequence

Use 50 minutes: eight for closed-book retrieval, ten for targeted explanation, twenty-seven for problems and graphs, five for error logging. Begin each session with one older question.

Read before calculating

A stress–strain graph routine

1. Read axis quantities, units and scale.
2. Find the initial straight region.
3. Calculate its gradient using widely separated points.
4. Identify proportional, elastic, yield and fracture features only if supported by the graph.
5. Interpret area as work per volume, not total work.
6. State whether unloading information is shown or merely assumed.

The OpenStax stress–strain discussion shows that different materials have characteristic curves. Do not label every bend with a memorised name when the data do not establish it.

Plan a safe investigation

Determine Young’s modulus of a wire

Measure original wire length L, diameter at several orientations and positions, and extension ΔL under a series of safe loads. Calculate cross-sectional area from the mean diameter. Add loads gradually within the school apparatus limit, never stand under suspended masses, and follow teacher supervision.

For each load, calculate F = mg, stress F/A and strain ΔL/L. Plot stress vertically against strain horizontally. The gradient of the initial straight region estimates Young’s modulus. Use a best-fit line rather than one pair of adjacent points.

Uncertainty in diameter matters strongly because A ∝ d². Explain this sensitivity in evaluation instead of listing “human error.”

Choose the first equation

Model-selection drills

For a hanging wire, start with tensile stress and strain. For fluid compressed equally from all directions, start with pressure and fractional volume change. For a block whose top slides sideways, start with tangential stress and shear strain. For energy stored in a linearly stretched specimen, start with graph area ½σε.

Create cards with situation on the front and four items on the back: deformation type, stress, strain and modulus. Include incomplete prompts where original length, area or volume is missing; state what extra measurement is needed.

Repair the cause

Elasticity error log and spaced review

Use labels: vocabulary, geometry, unit, model, graph, limit and algebra. “Used mm² as 10⁻³ m²” is geometry/unit. “Used Young’s modulus for pressure compression” is model. “Continued linear equation beyond yield” is limit.

Readiness

Exam checklist and self-test

• Deformation type is identified before formula choice.
• Area conversion is squared correctly.
• Stress has Pa units and strain is dimensionless.
• The relevant linear elastic assumption is stated.
• Graph gradient and area have physical meanings.
• Final trend agrees with force, length, area and modulus scaling.

Readiness means at least 80% on a fresh mixed set, correct graph labels and no repeated unit/model error after delayed review. For online or physical NEB tuition, call 9846662070 with the diagnostic and error log.

References and next steps

Sources and related study guides

• CDC Nepal: Physics Grade 11
• OpenStax: Stress, Strain and Elastic Modulus
• OpenStax: Elasticity and Plasticity
• OpenStax: Chapter 12 Problems
• PhET: Masses and Springs

Next study Heat & Temperature and connect thermal expansion to material stress. Scope and sources were checked on 2 August 2026; follow current CDC, NEB and college instructions if requirements change.

Rebuild formulas from definitions

A derivation and comparison workbook

Begin every page with σ = F/A and ε = ΔL/L. From Y = σ/ε, recover ΔL = FL/(AY). Replace A with πd²/4 to see why ΔL = 4FL/(πd²Y). This chain is more reliable than memorising several unrelated wire formulas.

Make a comparison grid. At fixed material and load, double length: extension doubles. Double diameter: extension becomes one quarter. Use two parallel identical wires: total area doubles, so extension halves. Put two segments in series: extensions add. State the arrangement before using a proportionality.

Connect Elasticity to Physical Quantities and dimensional checks. Stress and every elastic modulus have pressure dimension ML⁻¹T⁻², while strain is dimensionless. Energy density ½σε has J m⁻³, equivalent to Pa.

Finish with a boundary question: if the stress–strain graph bends beyond the proportional region, the constant-gradient relation cannot be applied across the entire interval. Write “linear elastic model no longer valid” before considering new data.