Physics Sumary P2
- Created by: Lucy1499
- Created on: 10-04-16 14:49
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- Physics Summary P2
- Forces and energy
- A resultant force shows the combined effect of several forces. It makes an object accelerate.
- The speed of an object can be found using a distance time graph. The acceleration and distance travelled 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
- The stopping distance of a vehicle is thinking distance plus braking distance
- Moving objects reach a terminal velocity (top speed) when drag forces matches driving forces
- Momentum is mass X velocity. It is conserved when objects collide or explode apart if no external forces act.
- A force transfers energy when it does some work on an object
- 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
- Electrical circuits
- Electric current is a flow of charge
- In a series circuit: the current is the same throughout, the potential difference is shared between components and the resitance of components adds
- Circuit diagrams use standard symbols
- Resistance measures how easily a current flows through a component. Resistance = potential difference current
- In a parallel circuit, the current is shared between branches and the potential difference is the same for each branch
- Using mains electricity safely and the power of electrical appliances
- Batteries supply direct current; mains supply is alternating at about 230V 50Hz
- Electric cable can be two-core or three-core. A three pin plug must be correctly wired
- Energy transferred is the potential difference supplied X charge
- Earthing, fuses and RCCBs protect the user and appliance
- Power is the potential difference supplied X current, or energy transferred time
- Atomic Structure and radioactivity
- An atomic nucleus contains protons and neutrons. Electrons orbit the nucleus. Radioactive materials emit ionising radiation from their nucleus
- Half-life is the time taken for the count rate of a radioactive sample to halve
- Alpha, beta, and gamma radiation have different properties, uses and dangers
- Background radiation comes from natural sources (e.g. rocks) and man made sources like medical uses
- Ions are atoms that have lost or gained electrons. Isotopes have the same number of protons, but different numbers of neutrons
- Nuclear fission and nuclear fusion
- Nuclear fission is the splitting of an atomic nucleus
- Fission of uranium- 235 or plutonium-239 during a chain reaction releases energy in nuclear reactors
- All stars have a life cycle. Nuclear fusion in stars releases energy and produces all naturally occurring elements
- Nuclear fusions is when two atomic nuclei join to form a larger one
- Forces and energy
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