P2 Summaries
- Created by: phoebe50227
- Created on: 16-12-16 20:06
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- P2 Summaries
- Forces and energy
- The stopping distance of a vehicle is thinking distance plus braking distance.
- A force transfers energy when it does some work on a object.
- Momentum is mass x velocity. It is conserved when objects collide or explode apart if no external forces act.
- The speed of an object can be found using a distance time graph. The acceleration and distance traveled can be found using a velocity time graph.
- Objects gain gravitational potential energy if they are lifted up. Moving objects have kinetic energy. Stretched or squashed elastic objects store elastic energy.
- A resultant force shows the combined effect of several forces. It makes an object accelerate (changes speed or direction).
- Moving objects reach a terminal velocity (top speed) when drag forces matches driving forces.
- Using mains electricity safely and the power of electrical appliances
- Electric cable can be two-cord or three-cord. A three pin plug must be correctly wired.
- Batteries supply direct current (d.c.); mains supply is alternating current (a.c.) at about 230V 50Hz.
- Power is the potential difference supplied x current, or energy transferred ÷ time.
- Earthing, fuses and RCCBs protect the user and appliance.
- Energy transferred is the potential difference supplied x charge
- Static electricity
- Insulating materials can be charged by rubbing. They gain or lose electrons.
- Objects carrying the same charge repel. Objects carrying the opposite charge attract.
- Atomic structure and radioactivity
- An atomic nucleus contains protons and neutrons. Electrons orbit the nucleus. Radioactive materials emit ionising radiation from their nucleus.
- Background radiation comes from natural sources (for example rocks,) and man-made sources (for example medical uses.
- Ions are atoms that have lost or gained electrons. Isotopes have the same number of protons, but different numbers of neutrons.
- Alpha, beta and gamma radiation have different properties, uses and dangers.
- Half-life is the time taken for the count rate of a radioactive sample to halve.
- Nuclear fission and nuclear fusion
- Nuclear fission is the splitting of an atomic nucleus.
- All stars have a life cycle. Nuclear fusion in stars releases energy and produces all naturally occurring elements.
- Fission of uranium-235 or plutonium-239 during a chain reaction releases energy in nuclear reactors.
- Nuclear fusion is when two atomic nuclei join to form a larger one.
- Electrical circuits
- In series circuit: the current is the same throughout, the potential difference is shared between components and the resistance of components adds.
- Circuit diagrams use standard symbols.
- In a parallel circuit, the current is shared between branches and the potential difference is the same for each branch.
- Resistance measures how easily a current flows through a component. Resistance = potential difference ÷ current.
- Electric current is a flow of charge.
- Forces and energy
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