Making Young’s Modulus Actually Teachable

Hemel Private Tuition – Practical Physics that Works

Young’s modulus is one of those A-level Physics experiments that ought to be conceptually beautiful but, in practice, often turns into a frustrating exercise in squinting at a vernier scale and arguing about micrometres.

Traditionally, students measure the extension of a long metal wire under load, often using a vernier scale or travelling microscope. It is technically correct — but also:

• fiddly

• time-consuming

• prone to large percentage uncertainties

• difficult for weaker practical students

• and not especially engaging

A Better Approach: Lascells Strip & Wire Testing Clamps

Using Lascells Strip & Wire Testing Clamps, we can transform the experiment into something that is:

• clear

• visual

• safe

• cheap

• and far more effective for teaching the physics rather than the micrometry

Instead of metal wires, students test plastic strips cut from carrier bags from different manufacturers. The behaviour is immediately visible, repeatable, and ideal for identifying key material properties.

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The Physics You Can Actually See

With increasing load, students can clearly observe:

• Elastic behaviour – the strip returns to its original length

• Limit of proportionality – extension no longer proportional to force

• Elastic limit – permanent deformation begins

• Ultimate tensile strength – the maximum force before failure

These concepts are often abstract when using metal wires. With plastic strips, they are obvious.

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Full Experimental Method

Apparatus

• Lascells Strip & Wire Testing Clamps

• Plastic carrier bags (cut into uniform strips)

• Metre ruler or fixed scale

• Mass hanger and slotted masses

• Clamp stand

• Safety tray (to catch masses if the strip fails)

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Method

1. Prepare the sample

   • Cut strips of equal width (e.g. 10 mm) from different plastic bags

   • Measure the original length $L_0$

2. Set up the clamps

   • Secure the plastic strip vertically between the Lascells clamps

   • Attach the lower clamp to a mass hanger

3. Apply load gradually

   • Add masses in equal increments (e.g. 50 g or 100 g)

   • After each addition, measure the extension

4. Record data

   • Force (N)

   • Extension (m)

   • Note any permanent deformation on unloading

     

5. Continue loading

   • Until the strip clearly leaves linear behaviour

   • Stop just before failure (or allow failure with eye protection and clear space)

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Results and Analysis

Typical Results Table

Load (N)	Extension (mm)
0.5	2
1.0	4
1.5	6
2.0	8
2.5	11
3.0	15

Graph

• Plot Force vs Extension

• The straight-line region shows Hooke’s Law

• The point where the graph curves marks the limit of proportionality

Discussion Points

• Why different plastics behave differently

• Why metals show a much smaller elastic region

• Why this experiment has larger extensions but smaller uncertainties

• Why real engineers test polymers differently from metals

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Why This Works Better Than the Traditional Wire Method

✔ No microscopes
✔ No long wires under tension across the lab
✔ No students struggling to read verniers
✔ No huge uncertainty in extension measurements
✔ Far safer — especially for mixed-ability groups
✔ Much cheaper equipment
✔ Much quicker
✔ Much clearer physics

For teaching Young’s modulus as a concept, this approach is outstanding.

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How We Use This at Hemel Private Tuition

In our laboratory and online TV-studio lessons, this experiment:

• reinforces material properties visually

• builds confidence in graph interpretation

• supports exam-quality evaluation answers

• works brilliantly for OCR, AQA, and Edexcel specifications

Students leave understanding why materials behave as they do — not just how to fill in a table.