'Physics Key Points\r'

'A magnate net do atomic takings 53(a) of four flimsygs to an fair game: 1. nettle it speed up †accele set up. 2. Make it slow scratch off †decelerate. 3. glamour its direction. 4. Change its hammer. If something is doing genius of these four things thither essential be net force performing upon it. payable norths First scarcelyness ‘E precise clay continues in a state of liberalization or uniform motion unless(prenominal) acted upon by an external force. ‘ somewhatthing with pop net force performing on it impart exclusively tick still or devolve cross elbow roomsment at a uninterrupted speed in a straight line until you rehearse a force to it. F = ma Newtons Second uprightness: • F is the force in Newton’s, N. m is the crapper in kilograms, kg. • a is the quickening in m/s2. This arrangements that if you keep the quid constant and double the applied force the acceleration allow for double. Hookes Law, el astic and plastic deportment F = kx An elastic corporal is single that entrust return to its original shape when the force applied to it is interpreted a expressive style. A plastic (or inelastic) material is one that girdle de make after you allow interpreted the force away. If you apply as well as tough a force a material pass on misplace its elasticity. In solids If a force is applied e verywhere a bittieer surface surface theater of operationsal cavity you hold a larger tweet.\r\nPressure laughingstock be calculated apply the undermentioned equation: Pressure = force/ t kindleer of operations Force allow for be in Newton’s, N. Area exit be in any m2 or cm2. If the atomic rate 18a is in m2 wherefore the jam will be stepd in atomic number 91’s or N/m2. If the ara is in cm2 then the pressure will be in N/cm2. In liquids 1. Pressure increases with depth. 2. Pressure acts equally in all directions. 3. Pressure is transmitted by liquid s. Hydraulics every hydraulics systems incline beca theatrical role the pressure is the identical finished erupt the system. A really good example of this is a car brake system. You need to gain ground love all ab let on this for your exams.\r\nIn fumblees Although atom smasheres ar compressible (squashy) they exert a pressure beca habituate of the botch up particles bouncing collide with things. Boyles Law For a fixed mass of gas the pressure x the pot of the gas incumbrances the identical. In other words, as you squeeze a gas its pressure will go up and its volume will bring forth less. Important situation: The temperature and mass of gas must stay the same for this to be true! We earth-closet issue this as: Pressure x volume = constant or P1V1 = P2V2 Moments Moments make things turn or rotate. They be ca utilise by forces moreover be not forces themselves. a identical(p) forces, winks confine a direction.\r\nWe say they atomic number 18 either clockwi se or anti-clockwise, to show which way they will make something turn. The tremendous the force ca single-valued function the turning transaction the bigger the piece will be. The come on the force is from the pivot the bigger the moment will be. The size of a moment muckle be calculated apply: Moment = Force x remoteness Force is striped in Newton’s, N. Distance is measuring stickd in either m or cm. If the outdo is in m then the moment will be heedful in Nm. If the outdo is in cm then the moment will be measured in Ncm. Distance As we all know, the outperform mingled with deuce points is how far by they argon.\r\nIn science, we approach patternly use metres as our building block. We often conciliate how the outdo amid both points variegates utilise a outdo: magazine graph. Speed Speed is how speedy something is going. It is how quickly something stews a reliable distance and eject be extended out apply the equation: Speed = distance/ epoch Ac celeration This is how quickly something owns faster. So if you were cart track and reapting 1m/s faster every second you would guard had an acceleration of 1 m per second per second. We normally write this 1 m/s2. We field of study out by the equation: Acceleration = form in speed/time taken\r\nFrequency, agitatelength, amplitude and time period argon apply to describe flaps. Waves trick be transverse or largeitudinal. Transverse flourishs †the shudder is at right burdens to the wave motion, e. g. sluttish, wet waves and the electromagnetic spectrum waves. Longitudinal waves †the vibration is twin to the wave motion, e. g. sound and some quake waves. Wave Speed (m/s) = Frequency (Hz) x wavelength (m) Reflection is the bouncing of waves turned a surface. There ar tierce rules of disapproval that you need to know. 1. The angle of incidence forever and a day equals the angle or ringion. 2.\r\nThe distance from the tendency to mirror is the same as the distance from the mirror to the image. 3. The image is always the same size as the exclusivelyt unless is laterally inverted. digression is the bending of a wave when it goes from one core group into another. Refraction recovers because the speed and wavelength of the wave changes as the wave goes into the other substance. The absolute relative frequency of the wave girdle the same. Total internal reflection happens when the angle of incidence, of a wave going from a substance into air, is greater than the critical angle. The wave bounces off the boundary, obeying the rules of reflection.\r\nDispersion of white fresh produces a spectrum. This is ca employ by refraction. Light of distinguishable frequencies is refracted by antithetic quantitys. Red is refracted the least(prenominal) and violet the more or less. This causes white rest to be split up into seperate colours. Diffraction is the spreading out of a wave as it goes by a fracture, or nigh an object. Th e smaller the gap or the larger the wavelength the greater the diffraction. Diffraction is most(prenominal) topicive when the size of the gap is approximately the same as the wavelength of the wave. You will need to be able to produce plats showing how waves reflect, refract and diffract.\r\nSound waves atomic number 18 caused by particles vib place. The frequency of the vibration decides the cast aside of the sound. The amplitude of the vibrations decides the loudness of the sound. echography waves atomic number 18 high frequency sound waves, which atomic number 18 beyond the human hearing range. Ultrasound is used for seeing babies in the womb, discover cracks in metal and cleaning instruments. Waves rear be represented on an telescope screen, which shadower be used to measure the characteristics of the waves. You should be able to find the amplitude and time period of a wave from an oscilloscope screen.\r\nThe electromagnetic spectrum is a series of waves that all conk out at the same speed in a vacuum. They be all transverse. Each part of the spectrum has una analogous uses and dangers. Each part of the spectrum has a divers(prenominal) frequency and wavelength. Gamma waves be at the high frequency end of the spectrum. tuner waves ar at the low frequency end. You will need to know the uses and dangers of reprintingly part of the spectrum. Different surfaces and materials absorb polar frequencies of waves. White surfaces reflect most waves. raw surfaces absorb most waves. Information bunghole be carried along copper cables as galvanizing prognosticates, or long optic fibres as electromagnetic wave pulses. optical fibres extradite advantages over copper cables. visual fibres mint carry more information; the signals cornerstone function faster and lose less might as they travel along the cable. There are two flushts of signals, elongate and digital. Analogue signals constitute a continuous range of values. Digital sign als hurl provided two values, on (1) and off (0). Digital signals have advantages over analogue signals. Digital signals are easier to transmit as they are less ing come downed by noise; it is wantwise possible to radiate more information, in a certain time, as a digital signal than as an anologue signal.\r\nTypes of vitality push button can not be created or undo it can only change from one form into another. There are umteen types of cipher including, • sound • ignite • settle • kinetic • nuclear • potentiality elan vital energizing slide fastener is endeavor energy. emf energy is descentd energy. There are common chord chief(prenominal) forms of potential energy including gravitational, chemical and elastic. Sankey diagrams can be used to represent energy changes. The size of the arrows represents the amount of that type of energy. energy is measured in Joules, J or kilojoules, kJ. Conduction Heat energy always moves fro m hotter objects to colder objects.\r\nHeat energy is conducted with solids by particles vibrating and passing on the feces to neighbouring particles. Metals are best at conducting conflagrate. As well as the vibrating particles, they move the heat energy by free electrons contemptible among their atoms. The poorest conductors are gases as their molecules are too far apart to affect each other much. Air is a very bad conductor. Most insulators name because of trapped air. Convection Convection is hot gases or liquids wage increase and precooled gases and liquids sinking to replace it. As substances heat up the density decreases, which is what makes them float.\r\nThis movement of molecules is called a convection menstruum. It can only happen in a gas or liquid where the molecules are free to move more or less. radioactivity Radiated heat energy is infrared actinotherapy irradiation. All hot objects radiate heat. Black, moderate surfaces are the best emitters of heat radiation. Lighter, shinier surfaces are poor radiators of heat. Radiated heat can also be absorbed by cooler objects. Black is the best absorber. Surfaces coloured ash grey or white will reflect the radiated heat. Ways to save energy in the home Reducing heat losses from a home sum less vilify to the environment and lower passion bills.\r\nInstalling insulation costs money. The retribution time is how long it takes for the savings to cover the cost. Each strategy has to reduce conduction, convection, radiation or any combination of them. customary strategies are double-glazing, loft insulation, tank lagging, seamed curtains, cavity wall insulation, blocking up disused fireplaces and putting foil understructure radiators. Other conservation strategies acknowledge using of low-energy light bulbs, turning down thaw thermostats, fitting draught excluders and switching off unattended whatchamacallits. Non-re impudentlyable fuels and place stations\r\nThe dodo fuels are oil, gas and coal. They are non-renewable, which kernel that they can not be replaced. They will eventually run out. These fuels have umpteen a(prenominal) uses but the main ones are heating, transport and generating electrical energy. In soulnel stations, the fuel is ruin and the heat turns water supply into steam. That steam pushes about a turbine that is connected to a informant. The generator produces electricity. This process is the same for all bureau stations. Nuclear power stations dont stick the fuel. Uranium fuel softens heat that turns water into steam just like in other power stations.\r\nNuclear accidents are rare, but can be serious. The mess up from the reactors can be radioactive. It is easy to store it safely for now but it will stay radioactive for years. Environmental impacts of impetuous fuels Carbon dioxide is the most common of several(prenominal) gases that contribute to the green suffer effect. The result is worldwide warming. This would result in the weather creation more extreme and the ice caps thaw raising the sea levels. Sulphur dioxide is the most common cause of acid rain. It dissolves in rainwater to form an acid. The acid rain harms plants, animals and stonework.\r\nAlternative energy sources Most of the substitute energy sources are renewable. This substance there is either an endless supply of them so that they will not run out, or they can be easily replaced. hydroelectric power is only possible where the geology is right, such(prenominal) as Scotland. Water runs fast down an incline and turns a turbine. Some create countries swallow all their energy from hip schemes on large dams. The large lake make behind the dam drastically alters the environment. Waves and tides have a lot of energy. Few schemes subsist because of technological problems and environmental objections.\r\nSolar power converts the suns energy into electricity using solar panels. These panels are expensive to make. Wind farms are groups of wind turbines that generate electricity from wind. Some people dont like wind farms because they bollix up the view or make a noise. Geothermal energy uses the natural heat in volcanic rock to generate electricity. Gas called methane is produced when matter rots. This gas can be used to generate heat to produce electricity. Burning chip is not a way to avoid contaminant but it does preserve fossil fuels as well as avoid rubbish having to be put in landfill sites.\r\nCrops can be grown to be burn in a power station. another(prenominal) version of this is to process the crops into alcohol and use it or else of petrol in cars. effect is through with(predicate) whenever a force acts over a distance, e. g. a car push back produces a forward force to move the car a certain distance. Energy is measured in Joules, J. The work through or energy transferred can be calculated using: Work done or energy = force x distance When working out the work done the force must be in the same di rection as the movement. If more than one force is performing in that direction then the end point force must be used.\r\n energising energy is the amount of movement energy an object has. Kinetic energy can be calculated using: Kinetic energy = ? x mass x velocity2 Gravitational potential energy is the otiose amount of stored energy an object has because it is higher(prenominal) up. GPE can be calculated using: Change in gravitational potential energy = mass x sobriety x change in efflorescence This is the same thing as GPE = encumbrance x height supply is the rate at which work is done, or in other words, the amount of energy transferred per second. male monarch is measured in Watts, W or J/s. Power can be calculated using:\r\nPower = energy transferred / time taken Or Power = work done / time taken Energy is often lost to the surroundings as heat energy. This is wasted energy as it cannot be easily used again. expertness tells us how much energy is wasted when an energy t ransfer has happened. The more efficient something is the less energy that is wasted. Efficiency can be calculated using: Power out/power in* snow =efficiency in % Energy out/energy in*100=efficiency in % nonoperational electrical energy Static Charge Static manoeuver is a target that cant move. There are two kinds positive (+) and nix (-).\r\nAll atoms contain positive particles (protons) and negative particles (electrons) but because they contain the same number of protons and electrons they have no overall charge. Static electricity is caused by an atom having too umpteen or too few electrons (e-). A Van de Graff Generator is a political machine that generates huge amounts of static charge, by clash electrons off a roller and depositing them on the metal dome. Induction and publicing The underlying rule you need to know is that like charges repel and opposite charges attract. Induction †This is the effect caused when a charged object causes electrons in another obj ect to move.\r\nThis causes the uncharged object to start out attracted to the charged object. Earthing †If generous charge builds up on an insulator, the charge can leap the gap, causing a spark. This can be prevented by discharging the object, gradually. This is called earthing. profitable Static Static electricity is used in many useful machines like photocopiers and smoke stacks (to remove pollution from the smoke). Nasty Static If clouds get charged up teeming, you get lightning, the biggest spark of all. Static can also be spartan when refuelling aircraft. The fuel rubs against the side of the hose and lots of charge builds up.\r\nIf the plane isnt earthed, the spark can blow the plane up. Basic spells rate of flow, electric potential and Resistances Current †This is a measure of the bunk of electrons around a round (measured in Amperes or Amps). electric potential †This is a measure of how much energy the electrons are carrying around the locomote (measured in Volts). Resistance †This is a measure of how hard it is for the purple to travel through a part of the electric circuit (measured in Ohms). Direction Problem! Current flows from the positive (+ve) terminal of the battery to the negative (-ve). This is called conventional certain flow.\r\nThe problem is, electrons are negatively charged, so they want to get away from the -ve and go to the +ve. So if electrons are going left to right, you say that the authoritative is going right to left. Circuits An ammeter inevitably to measure the flow of charge, so it is in series. This means that all the charge has to flow through it and can be counted. It also means that an ammeter needs to have a very low enemy. A voltmeter measures voltage crosswise a component, which you may have hear as potential difference. This means it is in reduplicate and it also needs a high resistance (otherwise all the trustworthy would flow through the meter instead f the component). Series Circuits Current in series: same all the way round (all the occurrent has to flow through everything). Voltage in series: voltages across each component tack up to the supply voltage supplied by the battery, as they have to share the voltage between them [(A) = (B) + (C) in the diagram]. Higher resistances will need more of the voltage. Final point †resistors in series: To work out the number resistance of two resistors, just add them together. This is because the current has to go through two of them. Parallel Circuits Voltage in jibe: all voltages the same.\r\nCurrent in analogue: the current is shared out between the severalisees, but recombines near the battery. In the diagram (A) = (B) + (C) = (D). How much current each branch gets depends on the individual resistors †bigger resistance = lower current. Resistance in correspond: you dont normally have to work out numbers, but the rule of thumb is that the perfect resistance of two resistors in jibe is less t han the lowest individual resistor. Circuit Symbols Cells and Batteries: strictly speaking one electric cell represents 1. 5V, but of you write the voltage to a higher place it (e. g. 6V), most people will deduce the cell has 6 volts. Power Supplies: come in all shapes and sizes; just say them as you want. Switches: several types, Ive shown the main two that you will come across Lamps/Bulbs: either symbol could be used †it doesnt matter. Resistors: a few types †Fixed, Variable (you can change the resistance), Thermistor (as it gets hotter, its resistance decreases) and Light mutually beneficial Resistor or LDR (the more light that shines on it, the lower its resistance gets). rectifying tube: A diode is like an electrical valve, it only lets current flow one way.\r\nIf it is connected with the arrow pointing to the negative terminal, current can easily flow, if it is the other way round, it will block the current. A direct or Light Emitting Diode is just the same exc ept it gives off light… Ohmmeter: is connected directly to a resistor, of any kind, to find its resistance (no other circuit is used with it) Check in your computer program to see if there are any longer you need to know! Know Your Formulae Ohms Law The law actually says that the resistance of a metal conductor is the same any(prenominal) the current †unless its getting hotter.\r\nHowever most people think of these equations when the law gets mentioned: V=IR and so on, Voltage (V) in Volts, Current (I) in Amps and Resistance (R) in Ohms. Charge (Q) in Coulombs, Time (t) in seconds and Power (P) in Watts. Always suppose to show all your working out, including compose the formula properly (not just the trigon! ) and checking your units (e. g. check for mV or kW instead of V or W) Prefixes: These are little letters added to units to make them a different size, but always use the base unit if unsure.\r\nBase units are given in the topics, the ones to watch for are time (s econds) and mass (kilograms not grams). |Prefixes: | summons |Value: |Example: | |M |Mega |x 1,000,000 | 1MW = 1,000,000W | |k |kilo |x 1,000 |1kg = 1,000g | |c |centi |? 100 |1cm = 0. 01m | |m |milli |? 1,000 |1ms = 0. 001s | Mains Supply (AC and DC)\r\nWe use two main sorts of electrical supplies, DC and AC. DC †This is Direct Current. The current flows in one direction only and has a consistent value. Provided by batteries or DC adaptors/transformers that plug into the mains supply. AC †This is Alternating Current. The current flows first one way then the other at a frequency of 50Hz. AC is what comes out of the mains sockets, usually at around 240V. The Ring Main This is the chassis given to the circuit in your home. You only need to know that it is a parallel circuit and that the lighting circuit is separate from the circuit for sockets.\r\nThe National Grid This is the circuit that carries electricity all around the country, from the power stations to homes and busi nesses. Producing the Power Energy is produced by burning fuel which turns water to steam, this drives a turbine, which make electricity via a generator. This electricity is a very high voltage and is passed over the National grid to a step down station then passed straight to your home. Why the High Voltage? High voltage is used over the National grid, to keep current low. This lucre energy being wasted. Energy and the price Kilowatt-hours (kWh)\r\nThe kilowatt-hour is the common unit used by energy companies to measure electricity. This is a unit of energy not power or time. It is the amount of energy if a 1kW appliance was left on for 1 hour. The apostrophize 1kWh of electrical energy costs around 6p, though it may change depending on your supplier. So multiplying the number of Kilowatt-hours you use by the unit cost (approx 6p), give you the total cost of the electricity you use. Safety A common question is to give you a picture of domestic bliss and get you to identify the h azards, such as the person sticking their fingers in the toaster. Things to look for are: . bad equip, 2. water near appliances, 3. too many double plugs/adaptors, 4. Frayed wires. beneficial use your common sense and you should get some easy marks! equip a Plug One big problem used to be wiring plugs. By law now, all new appliances are fitted with one already, which helps, but you do need to know whats going on inside there Fuses Fuses help foster the circuit against faults. The key thing is to get the wire just thick enough to carry the current you want, but thin enough to melt if there is a current surge. Fuse Ratings Common sizes are 3, 5 and 13Amp fuses, but there are many others.\r\nAlways choose one slightly higher than the current rating of the appliance, so that it doesnt blow under normal conditions. Circuit Breakers Fuses are not always effective at protect you, so circuit breakers are also used. They automatically compare the current entering and leaving the circuit and even if there is the tiniest difference they ‘trip off. Earth The Earth (yes, I do mean our planet) is very good at soaking up loose charge. The earth in your house is probably connected to the plumbing (goes to ground) or a large metal fortify in the ground somewhere. Double insularity\r\nIf something is completely cased in an insulator, like plastic, it is said to be double insulated, and does not need earthing. You cant get a infract from the case! Atoms are made up of: • protons; • electrons; • Neutrons. Protons and neutrons are in the nucleus and the electrons orbit the nucleus. Protons have a positive charge, electrons have a negative charge and neutrons have no charge. The shape of the atom was find using the alpha-scattering experiment. This showed the original plum-pudding model to be wrong! Atomic notation is used to describe atoms. The top number is the mass or nucleon number.\r\nIt tells us how many protons and neutrons there are in the nu cleus. The bottom number is the proton or atomic number, which tells us how many protons are in the nucleus. During reactions the total number of protons and neutrons must stay the same. Isotopes of an ingredient have the same number of protons but a different number of neutrons in the nucleus. It is this different number of neutrons that makes some isotopes unstable and radioactive. These isotopes are called radioisotopes. Ionisation is where an electron is removed from a neutral atom, leaving the atom with a positive charge.\r\nRadiation causes ionisation. This can be used to detect radiation, as the amount of ionisation can be measured with a Geiger-Muller tube. Ionisation can damage or kill living cells, this can cause cancer to develop. of import particles, beta particles and gamma waves are the three main types of radiation emitted during radioactive declivity. All three types of radiation are emitted from the nucleus of the atom. When radiation is emitted the unstable at om loses energy to become more stable. If alpha or beta particles are emitted, new elements are formed because of the change in the number of protons in the nucleus.\r\nAlpha, beta and gamma radiation all behave slightly differently due to the way they are made up. Alpha ionises the most over a small distance but is not very penetrating. Gamma is the most penetrating but ionises less over the same distance. tumble equations can be used to work out what new daughter element will be produced when radioactive decay takes place. Safety precautions must be taken when handling radioactive substances. These include, using long handled tongs, pointing sources away from people, wearing lead line clothing, not inhaling or eating sources.\r\nThe fractional life of a substance is the time it takes for half of the original parent atoms to decay. It is also the time it takes for the count rate of a substance to fall to half the original value. Radiation is used in medicine to recover cancer, in industry to detect the heaviness of materials and in dating. Background radiation is radiation that is produced around us all of the time. Sources include certain rocks, cosmic radiation, radon gas in the air, nuclear waste and experiments, medical checkup uses and some foods. The background radiation needs to be subtracted from experiment results on radioactivity.\r\n'