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P8: Global challenges

P8.1 Global Challenges Part 1

P8.1a – recall typical speeds encountered in everyday experience for wind and sound, and for walking, running, cycling and other transportation systems

P8.1b – estimate the magnitudes of everyday accelerations

P8.1c – make calculations using ratios and proportional reasoning to convert units and to compute rates

P8.1d – explain methods of measuring human reaction times and recall typical results

P8.1e – explain the factors which affect the distance required for road transport vehicles to come to rest in emergencies and the implications for safety

P8.1f – estimate how the distances required for road vehicles to stop in an emergency, varies over a range of typical speeds

P8.1g – explain the dangers caused by large decelerations

P8.1h – estimate the forces involved in typical situations on a public road

 P8.2 Global Challenges Part 2

PM8.2i – apply: potential difference across primary coil (V) x current in primary coil (A) = potential difference across secondary coil (V) x current in secondary coil (A)

P8.2a – describe the main energy sources available for use on Earth, compare the ways in which they are used and distinguish between renewable and non-renewable sources

P8.2b – explain patterns and trends in the use of energy resources

P8.2c – recall that, in the national grid, electrical power is transferred at high voltages from power stations, and then transferred at lower voltages in each locality for domestic use

P8.2d – recall that step-up and step-down transformers are used to change the potential difference as power is transferred from power stations

P8.2e – explain how the national grid is an efficient way to transfer energy

P8.2f – link the potential differences and numbers of turns of a transformer to the power transfer involved; relate this to the advantages of power transmission at high voltages

P8.2g – recall that the domestic supply in the UK is a.c. at 50Hz and about 230 volts

P8.2h – explain the difference between direct and alternating voltage

P8.2i – recall the differences in function between the live, neutral and earth mains wires, and the potential differences between these wires

P8.2j – explain that a live wire may be dangerous even when a switch in a mains circuit is open, and explain the dangers of providing any connection between the live wire and earth

P8.1i – estimate, for everyday road transport, the speed, accelerations and forces involved in large accelerations


 P8.3 Global Challenges Part 3

P8.3a – explain the red-shift of light as seen from galaxies which are receding (qualitative only). The change with distance of each galaxy’s speed is evidence of an expanding universe

P8.3b – explain how red shift and other evidence can be linked to the Big Bang model

P8.3c – recall that our Sun was formed from dust and gas drawn together by gravity and explain how this caused fusion reactions, leading to equilibrium between gravitational collapse and expansion due to the energy released during fusion

P8.3d – explain that all bodies emit radiation, and that the intensity and wavelength distribution of any emission depends on their temperatures

P8.3e – recall the main features of our solar system, including the similarities and distinctions between the planets, their moons, and artificial satellites

P8.3f – explain for circular orbits, how the force of gravity can lead to changing velocity of a planet but unchanged speed (qualitative only)

P8.3g – explain how, for a stable orbit, the radius must change if this speed changes (qualitative only)

P8.3h – explain how the temperature of a body is related to the balance between incoming radiation absorbed and radiation emitted; illustrate this balance using everyday examples and the example of the factors which determine the temperature of the Earth

P8.3i – explain, in qualitative terms, how the differences in velocity, absorption and reflection between different types of waves in solids and liquids can be used both for detection and for exploration of structures which are hidden from direct observation, notably in the Earth’s core and in deep water