Identical detectors at equal distances from two heated plates record infrared signal after the background reading has been subtracted. Both plates have the same area and temperature. Matt black gives 8.4 units and shiny silver gives 2.1 units.
.1
Calculate how many times larger the black-plate signal is.
[2 marks]
.2
Evaluate whether the measurements support using a shiny surface to reduce thermal radiation losses.
[3 marks]
7 marksHigher
Spec and skills
Original practice question
Answer and supported method checks
A spring stores 0.72 J when compressed by 0.060 m. It obeys Hooke's law throughout this compression. It launches an initially stationary 0.090 kg toy horizontally; 25% of the stored energy is dissipated.
.1
Calculate the spring constant.
[2 marks]
.2
Calculate the toy's speed when it leaves the spring.
[3 marks]
.3
Explain why the speed cannot be found by treating the dissipated energy as destroyed.
[2 marks]
6 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
A detector registers 96 counts per minute of background radiation. With a source present it registers 896 counts per minute initially and 496 counts per minute after 12 minutes.
.1
Calculate the initial corrected detected count rate in min−1 (counts per minute).
[2 marks]
.2
Determine the half-life in minutes.
[2 marks]
.3
Explain why the background must be subtracted before comparing the rates.
[2 marks]
5 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
A pure liquid cools at a steady rate of energy loss. Its temperature falls from 60 °C to 40 °C in 4 minutes, stays at 40 °C for 6 minutes, then falls below 40 °C.
024681012203040506070Time (min)Temperature (°C)
.1
Calculate the average rate of temperature decrease during the first 4 minutes, in °C per minute.
[2 marks]
.2
Explain the horizontal section and the fall afterwards on the temperature-time graph.
[3 marks]
5 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
A car has thinking distance 10 m and braking distance 18 m on a dry road. On a wet road at the same initial speed, its thinking distance is still 10 m and braking distance is 30 m.
.1
Calculate the percentage increase in total stopping distance on the wet road.
[3 marks]
.2
Explain why wet conditions increase braking distance in this comparison.
