An engineer wants heated pipework to lose energy to its surroundings as slowly as possible. Identical pipe sections with finishes R and S are filled with equal volumes of water at the same starting temperature. The temperature decrease of the water after 10 minutes is measured in three trials.
| Finish | Trial 1 temperature decrease in °C\degree\text{C}°C | Trial 2 temperature decrease in °C\degree\text{C}°C | Trial 3 temperature decrease in °C\degree\text{C}°C |
|---|---|---|---|
| R | 11.8 | 12.0 | 12.2 |
| S | 7.8 | 8.0 | 8.2 |
The engineer changes the finish of the pipework from R to S. To the nearest whole number, by what percentage does this reduce the mean temperature decrease?
33%33\%33%
50%50\%50%
40%40\%40%
4%4\%4%
96 exam-style questions on Edexcel GCSE Physics 5.3 Black body radiation, covering 5.3.1 Emission of radiation and temperature, 5.3.2 Radiation balance and constant temperature, and 5.3.3 The temperature of the Earth. Each one has a worked solution and a mark scheme showing where the marks go.