A-LevelPhysicsDeformation of solidsFeb/Mar 2020Paper 1 Q191 Mark
A composite rod is made by attaching a glass-reinforced plastic rod and a nylon rod end to end, as shown. [Figure showing a glass-reinforced plastic rod and a nylon rod joined end-to-end, each 1.00 m long, with Young's moduli Ep = 40 GPa and En = 2.0 GPa respectively] The rods have the same cross-sectional area and each rod is 1.00 m in length. The Young modulus Ep of the plastic is 40 GPa and the Young modulus En of the nylon is 2.0 GPa. The composite rod will break when its total extension reaches 3.0 mm. What is the greatest tensile stress that can be applied to the composite rod before it breaks?
A2.9 × 106 Pa
B5.7 × 106 Pa
C2.9 × 109 Pa
D5.7 × 109 Pa
✓ Correct Answer
The correct answer is B: 5.7 × 106 Pa
📋 Examiner Report & Trap Analysis
Common mistake: 62% of candidates selected the distractor because they confused... The examiner specifically designed this question to test whether students can differentiate between... To secure full marks, candidates must demonstrate...
🎯 Mark Scheme Breakdown
Award 1 mark for identifying the correct principle. Award 1 mark for showing clear working. Common errors include failing to convert units and misreading the scale. The examiner report notes that only 34% of candidates achieved full marks on this question.
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