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
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]
4 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
A vibrating string is observed with a ruler in its plane. Its equilibrium position is at 12.0 cm on the ruler. The highest and lowest positions are 14.4 cm and 9.6 cm.
.1
Calculate the amplitude in metres.
[2 marks]
.2
A pupil says that increasing amplitude necessarily increases frequency. Evaluate the claim.
[2 marks]
5 marksHigher
Spec and skills
Original practice question
Answer and supported method checks
In a collision test the total momentum before impact is 0.500 kg m/s. Three repeats give total momentum after impact of 0.492, 0.501 and 0.495 kg m/s, all in the original direction.
.1
Calculate the mean total momentum after impact.
[2 marks]
.2
The uncertainty in the mean is estimated as 0.010 kg m/s. Evaluate whether these results contradict conservation of momentum.
[3 marks]
5 marksHigher
Spec and skills
Original practice question
Answer and supported method checks
A passenger stands in a bus moving at constant velocity. The bus brakes suddenly. The passenger is not holding a support.
.1
Explain why the passenger initially moves forwards relative to the bus.
[3 marks]
.2
A safety rail exerts a mean horizontal force of 180 N on a 60 kg passenger. Calculate the magnitude of the passenger's acceleration.
