A-LevelPhysicsDynamicsOct/Nov 2018Paper 2 Q311 Marks
(a) State the principle of conservation of momentum. (b) The propulsion system of a toy car consists of a propeller attached to an electric motor, as illustrated in Fig. 3.1. [Figure 3.1] The car is on horizontal ground and is initially held at rest by its brakes. When the motor is switched on, it rotates the propeller so that air is propelled horizontally to the left. The density of the air is 1.3 kg m⁻³. Assume that the air moves with a speed of 1.8 ms⁻¹ in a uniform cylinder of radius 0.045 m. Also assume that the air to the right of the propeller is stationary.
📋 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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