A design team is choosing recycled sheet material for a reusable package. (a) Write a research question about sheet thickness and midpoint deflection under load. [2] (b) Give and justify a hypothesis. [3] (c) Design a method using five thicknesses, a fixed support span and small masses. Identify variables, repeats, measurements, safety and the graph to draw. [6] (d) Explain one limitation that repeats do not remove and a matching improvement. [3] Do not invent results.

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Vary sheet thickness and measure midpoint deflection under the same force, span and specimen geometry. Predict that thicker sheets deflect less, then use repeated loading measurements and a deflection–thickness graph to test the relationship. (a) A focused question is: How does the measured thickness of an equal-width recycled sheet affect its midpoint deflection under a fixed load across a fixed support span? (b) Predict that deflection decreases as thickness increases because distributing material farther from the neutral layer increases bending stiffness. This predicts a direction without pretending the exact exponent is already known. (c) Measure each specimen's thickness at several positions with a micrometer. Cut equal widths and lengths, place each across the same two supports, add the same small central load and measure vertical deflection against a fixed scale or from calibrated photographs. (c) Thickness is independent and deflection is dependent. Control material batch, width, span, grain direction, load, load position, loading time, temperature and whether a specimen has previously been bent. (c) Test at least five thicknesses and three fresh specimens per thickness. Record raw thickness and deflection with units, calculate mean and range, and plot mean deflection against measured thickness with uncertainty visible. (c) Keep fingers clear of loads, use a tray for falling masses and stay well below sudden-failure loads. Stop and replace any creased specimen rather than quietly reusing it. (d) Lamination adhesive or fibre orientation may change with nominal thickness, producing a material-structure difference rather than thickness alone. Build specimens from the same layer stock, standardise adhesive mass and alternate test order.

Design a fair material-stiffness comparison

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