A-LevelPhysicsDynamicsMay/June 2012Paper 1 Q121 Mark
Two spheres approach each other along the same straight line. Their speeds are u₁ and u₂ before collision. After the collision, the spheres separate with speeds v₁ and v₂ in the directions shown below. [Figure 12.1] Which equation must be correct if the collision is perfectly elastic?
Au₁ - u₂ = v₂ + v₁
Bu₁ - u₂ = v₂ - v₁
Cu₁ + u₂ = v₂ + v₁
Du₁ + u₂ = v₂ - v₁
✓ Correct Answer
The correct answer is D: u₁ + u₂ = v₂ - v₁
📋 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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