Tutopiya: Study Resources for IGCSE, IB, GCSE & A-Levels

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1
Which is NOT one of AQA's three named methods to reduce unwanted energy transfers?
Answer & explanation
Correct: option D
Refrigeration is not on the spec list. The three are lubrication, streamlining and (thermal) insulation.
2
When a moving car brakes to a stop, where does most of its kinetic energy end up?
Answer & explanation
Correct: option B
Friction at the brake discs converts kinetic energy into the thermal store of the discs (and a smaller amount into the tyres and road).
3
Why is trapped air a good thermal insulator?
Answer & explanation
Correct: option B
Air conducts heat poorly (0.025 W/m·K), and trapping it stops convection currents that would otherwise carry heat away.
4
In RP2, which is a suitable control variable?
Answer & explanation
Correct: option B
Volume of water must be kept the same so heat loss rates can be fairly compared. Material is the independent variable; temperature is the dependent variable.
5
Doubling the thickness of loft insulation roughly:
Answer & explanation
Correct: option B
Rate of conduction is roughly inversely proportional to thickness — double the thickness, halve the rate of energy loss.
6
Streamlining reduces:
Answer & explanation
Correct: option B
Streamlining shapes a body to reduce air (or water) resistance.