A-LevelPhysicsSuperpositionOct/Nov 2017Paper 5 Q215 Marks
A student is investigating stationary waves on a stretched elastic cord. A vibrator attached to the cord is connected to a signal generator. The apparatus is set up as shown in Fig. 2.1. [Figure 2.1] The mass M attached to the cord is adjusted until resonance is obtained. The number n of antinodes on the stationary wave is recorded. The experiment is repeated with different masses to obtain different values of n. It is suggested that M and n are related by the equation f = n / (2L) * sqrt(Mg / μ) where f is the frequency of the vibrator, g is the acceleration of free fall, L is the length of the elastic cord and μ is the mass per unit length of the elastic cord.
📋 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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