A-LevelPhysicsDynamicsOct/Nov 2012Paper 1 Q131 Mark
Two identical, perfectly elastic spheres have the same mass m. They travel towards each other with the same speed v along a horizontal frictionless surface. [Figure showing two spheres colliding] Which statement about the sum of the kinetic energies of the spheres is correct?
AThe sum of their kinetic energies before impact is zero.
BThe sum of their kinetic energies before impact is ½ mv².
CThe sum of their kinetic energies after impact is zero.
DThe sum of their kinetic energies after impact is mv².
✓ Correct Answer
The correct answer is D: The sum of their kinetic energies after impact is mv².
📋 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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