Hospitals use X-rays to form images of the inside of the body. A CT scan uses X-rays from many directions. The table shows some typical radiation doses.
Typical radiation dose in millisieverts: one chest X-ray 0.02; one CT scan of the chest 7.0; background radiation in one year, UK average, 2.7.
Source of radiation
Typical dose in mSv
One chest X-ray
0.02
One CT scan of the chest
7.0
Background radiation in one year (UK average)
2.7
.1
Calculate how many chest X-rays give the same dose as one CT scan of the chest.
[2 marks]
.2
Calculate the dose from one CT scan of the chest as a percentage of the yearly background dose.
[2 marks]
.3
A patient has had a cough for several months. Evaluate the use of a CT scan of the chest to find the cause.
[3 marks]
.4
Give one harmful effect of ultraviolet radiation on the human body.
[1 mark]
6 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
A country needs a new power station. It could build a hydroelectric power station in a mountain valley or a gas-fired power station near a town.
Comparison of two power stations. Hydroelectric: fuel cost none; carbon dioxide when generating none; start-up time about 1 minute; building cost very high; needs a flooded valley. Gas-fired: fuel cost high; carbon dioxide when generating yes; start-up time about 15 minutes; building cost medium; can be built near towns.
Feature
Hydroelectric
Gas-fired
Fuel cost
None
High
Carbon dioxide when generating
None
Yes
Start-up time
About 1 minute
About 15 minutes
Building cost
Very high
Medium
Site
Needs a flooded valley
Can be built near towns
Evaluate the two options. Use information from the table and your own knowledge.
[6 marks]
6 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
A tired driver is driving fast on a wet road at night.
Explain how each of these factors affects the stopping distance of the car.
[6 marks]
4 marksFoundation
Spec and skills
Original practice question
Answer and supported method checks
An electric kettle has an input power of 2000 W. The useful power output, heating the water, is 1800 W.
.1
Calculate the efficiency of the kettle.
[2 marks]
.2
Calculate the power wasted by the kettle.
[1 mark]
.3
Give one way energy is wasted by the kettle.
[1 mark]
6 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
An electric motor in a lift raises the lift through a height of 12 m in 20 s. The mass of the lift is 800 kg.
Gravitational field strength = 9.8 N/kg.
.1
Calculate the energy transferred to the lift's gravitational potential store.
[2 marks]
.2
Calculate the useful power output of the motor.
[2 marks]
.3
A second motor raises the same lift through the same height in 30 s.
Explain why the second motor has a lower power output.
