AQA Physics 2

AQA Physics 2

Motion
1. 1.1 Distance-time graphs
  1. These are used to describe the motion of an object
  2. Speed (m/s) = distance (m) / time (s)
  3. Keywords: Speed
2. 1.2 Velocity and acceleration
  1. The velocity of an object is its speed in a given direction
  2. If an object change direction but has the same speed, its velocity still stays the same
  3. a = (v - u) / t
  4. Keywords: Velocity, Acceleration, Deceleration
3. 1.3 More about velocity-time graphs
  1. The gradient of the line on a velocity-time graph represents acceleration
  2. The area under the line of a velocity-time graph represents the distance travelled in a given time
4. 1.4 Using graphs
  1. The gradient of a graph is an object's speed on a distance-time graph
  2. The gradient of a graph is an object's acceleration on a velocity-time graph
  3. The area under a velocity-time graph is the distance travelled over that time period
  4. Always use the measurements from the graph in calculations
Forces
1. 2.1 Forces between objects
  1. Forces are measured in newtons (N)
  2. Objects always exert equal and opposite forces
  3. Keywords: Force, Newton
  4. An example of equal and opposite forces is driving along a road
2. 2.2 Resultant Force
  1. When resultant force is 0 an object is either at rest or continues moving at the same speed in the same direction
  2. Keyword: Resultant force
  3. When resultant force is not 0, an object will accelerate from rest, accelerate or deccelerate
3. 2.3 Force and acceleration
  1. F = m x a
  2. A resultant force always causes acceleration
  3. The greater the resultant force, the greater the acceleration
  4. Keyword: Mass
4. 2.4 On the road
  1. If a vehicle travels at a steady speed along the road, the resultant force is zero
  2. The faster the speed of a vehicle, the bigger the deceleration needed
  3. Stopping distance is thinking distance + braking distance
    1. Both TD and BD can be increased through drugs and alcohol or conditions
  4. Keywords: Stopping distance, thinking distance, braking distance
5. 2.5 Falling objects
  1. An object accelerates to the earth's surface at 9.81m/s²
  2. F = m x a
  3. W (N) = m x g
  4. If an object is on earth, g is called gravitational field strength
  5. If an object falls through a fluid, the fluid exerts a drag force on the object
  6. The object can only accelerate to a certain speed, called terminal velocity
  7. Keywords: Weight, gravitational field strength, drag force, terminal velocity
6. 2.6 Stretching and squashing
  1. F = k x e (Hooke's Law)
  2. Keywords: Elasticity, directly proportional, limit of proportionality, Hooke's law
  3. Objects and materials that extend when weight is placed on them are called elastic
  4. k = the spring constant in newtons per m, N/m. The stiffer a spring, the greater its spring constant
  5. When an object is stressed, work is done. This is stored as elastic potential
7. 2.7 Force and speed issues
  1. Reducing the speed of a vehicle reduces the amount of fuel it uses per mile
  2. Reducing air resistance also improves fuel economy
  3. Speed cameras are used to discourage speeding
  4. Anti-skid surfaces are used to prevent skidding
Work, energy and momentum
1. 3.1 Energy and work
  1. When an object moves, a force must have been applied
  2. Both work and energy have the unit joule, J
  3. W = F x d
  4. Work done = energy transferred
  5. Work done to overcome friction is mainly transferred into energy by heating
  6. Keywords: Work, friction
2. 3.2 Gravitational potential energy
  1. GPE is energy stored in an object because of its position in Earth's gravitational potential
  2. E = m x 9.81 x h
  3. Power is the rate of transfer of energy
  4. P = E / t
  5. Keywords: Gravitational potential energy, power
3. 3.3 Kinetic energy
  1. All moving objects have kinetic energy. The greater the mass, the faster the speed
  2. E = 1/2 x m x v²
  3. Keywords: Kinetic energy, elastic potential energy
4. 3.4 Momentum
  1. All moving objects have momentum. The greater the mass and velocity and the greater the momentum
  2. p = m x v
  3. Momentum is conserved whenever objects interact, provided no external forces act on them
  4. Keywords: Momentum, conservation of momentum
5. 3.5 Explosions
  1. p = m x v
  2. Like velocity momentum has both size and direction
  3. When two objects push each other, they move apart at different speeds if they are unequal weights
6. 3.6 Impact forces
  1. When vehicles collide, the force of the impact depends on mass, change of velocity and the duration of impact
  2. When two vehicles collide they exert equal and opposite forces on one another
  3. Keywords: Impact time, crumple zone
7. 3.7 Car safety
  1. Seat belts and air bag spread the force across the chest and increase the impact time
  2. Side impact bars and crumple zones 'give way' in an impact so increasing the impact time
  3. We can use the conservation of momentum to find the speed of a car before impact
Current electricity
1. 4.1 Electrical charges
  1. Certain insulating materials become charged when rubbed together
  2. Electrons are transferred when objects become charged
  3. Like charges repel, unlike charges atract
  4. Keywords: Insulating, electron, attract, repel
2. 4.2 Electric circuits
  1. Every component has its own agreed symbol
  2. I = Q / t
3. 4.3 Resistance
  1. V = W / Q = E / Q
  2. R = V / I
  3. Ohm's law states that the current through a resistor at constant temperature is directly proportional to the potential difference across the resistor
  4. Reversing the current through a component reversing the potential difference across it
  5. Keywords: Series, potential difference, parallel, volt (V), resistance, Ohm's law, ohmic conductor
4. 4.4 More current-potential difference graphs
  1. In a filament bulb, resistance increases with increase of the filament temperature
  2. In a diode the forward resistance is low and the reverse high
  3. In a thermistor, resistance increases as temperature decreases
  4. In a light-dependent resistor, resistance decreases as light intensity decreases
  5. Keywords: Filament bulb, diode, light-dependent resistor, thermistor
5. 4.5 Series circuits
  1. In a series circuit, the current is the same in each component
  2. Adding the potential differences gives the total potential difference
  3. Adding the resistances gives the total resistance
  4. I = V / R
6. 4.6 Parallel circuits
  1. For components in parallel, the total current
  2. The bigger the resistance of a component, the smaller the current is
  3. In a parallel circuit the potential difference is the same across each component
Mains Electricity
1. 5.1 Alternating current
  1. Direct current is in one direction only. Alternating current repeatedly reverses its current
  2. The peak voltage of an alternating potential difference is the maximum voltage measured from 0 volts
  3. f = 1 / T
  4. Keywords: Direct current, alternating current, frequency, live wire, neutral wire, oscilloscope
2. 5.2 Cables and plugs
  1. Sockets and plugs are made of stiff plastic materials, which enclose the electrical connecions
  2. Cables consist of 2 or 3 insulated copper wires surrounded by an outer layer of flexible plastic material
  3. In a 3 pin plug or cable there is a live (brown), neutral (blue) and earth wire (green/yellow)
  4. Keywords: Socket, cable, 3-pin plug
3. 5.3 Fuses
  1. A fuse contains a thin wire that heats up and melts if too much current passes through it which cuts the current
  2. A circuit breaker is an electromagnetic switch that opens and cuts the current off if too much current passes through it
  3. Keywords: Fuse, circuit breaker, residual current circuit breaker (RCCB)
4. 5.4 Electrical power and potential difference
  1. The power supplied to a device is the energy transferred to it each second
  2. P = I x V
  3. The correct rating for a fuse is power (watts) / volts
5. 5.5 Electrical energy and charge
  1. An electrical current is the rate of flow of charge
  2. Q = I x t
  3. When charge flows through a resistor, energy transferred to a resistor makes it hot
  4. E = V x Q
6. 5.6 Electrical issues
  1. Electrical faults are dangerous because they can cause electric shocks and fires
  2. Never touch a mains appliance with wet hands. Never touch a bare wire or terminal at a potential difference of more than ≥ 30 v
  3. Check cables, plugs and sockets for damage regularly
Radioactivity
1. 6.1 Observing nuclear radiation
  1. A radioactive substance contains unstable nuclei that become stable by emitting radiation
  2. There are 3 main types of radiation from radioactive substances, alpha (α), beta (ß) and gamma (Γ)
  3. Radioactive decay is a random event and we cannot influence or predict when it'll happen
  4. Background radiation is from radioactive substances in the environment, space or X-rays
  5. Keywords: Nucleus, proton, neutron, electron, alpha, beta, gamma (radiation)
2. 6.2 The discovery of the nucleus
  1. Rutherford used the measurements from alpha particle scattering experiments as evidence that an atom has a small positively charged central nucleus where most of the mass of the atom is located
  2. The nuclear model of the atom correctly explained why the alpha particles are scattered and why some are scattered through larger angles
3. 6.3 Nuclear reactions
  1. Isotopes of an element are atoms with the same number of protons but different number of neutron. Therefore they have the same atomic numbers but different mass numbers
  2. Alpha decay is a loss of 2 protons and neutrons from the nucleus
  3. Beta decay is when a neutron in the nucleus changes into a proton and an electron
  4. Keywords: Ion, isotope, atomic number, mass number
4. 6.4 More about different radiation types
  1. α radiation is stopped by paper or a few cm of air
  2. ß radiation is stopped by thin metal or roughly 1m of air
  3. Γ radiation is stopped by thick lead and has an unlimited range in air
  4. A magnetic or an electric field can be used to separate a beam of alpha, beta and gamma radiation
  5. Alpha, beta and gamma radiation ionise substances they pass through
  6. Keyword: Ionisation
5. 6.5 Half-life
  1. The half-life of a radioactive isotope is the average time it takes for the number of nuclei of the isotope in a sample to halve
  2. The activity of radioactive source is the number of nuclei that decay per second
  3. The number of atoms of a radioactive isotope and the activity both decrease by half every half-life
  4. Keyword: Half-life
6. 6.6 Radioactivity at work
  1. The use we can make of a radioactive isotope depends on its half-life, and the type of radiation it gives out
  2. For radioactive dating of a sample, we need a radioactive isotope that is present in the sample which has a half-life about the same as the age of the sample
  3. Keywords: Tracer, radioactive dating
Energy from the nucleus
1. 7.1 Nuclear fission
  1. Nuclear fission is the splitting of a nucleus into two approximately equal fragments and the release of 2 or 3 neutrons
  2. Nuclear fission occurs when a neutron hits a uranium-235 or plutonium-239 nucleus which splits it
  3. A chain reaction occurs when neutrons from fission go on to cause other fission events
  4. In a nuclear reactor control rods absorb fission neutrons to ensure that, on average, only one neutron per fission goes on to produce further fission
  5. Keywords: Nuclear fission, chain reaction
2. 7.2 Nuclear fusion
  1. Nuclear fusion is the process of forcing two nuclei close enough together so they form a single larger nucleus
  2. Keywords: Nuclear fusion
  3. Energy is released when two light nuclei are fused together
3. 7.3 Nuclear issues
  1. Radon gas is an α-emitting isotope that seeps into houses in certain areas through the ground
  2. There are thousands of fission reactors safely in use throughout the world. None of them are of the same type as the Chernobyl reactors that exploded
  3. Nuclear waste is stored in safe and secure conditions for many years after unused uranium and plutonium is removed from it
4. 7.4 The early universe
  1. A galaxy is a collection of billions of stars held together by their own gravity
  2. Before galaxies and stars formed, the universe was formed of hydrogen and helium
  3. The force of gravity pulled matter into galaxies and stars
  4. Keywords: Gravitational attraction, star
5. 7.5 The life history of a star
  1. Keywords: Protostar, main sequence star, red giant, white dwarf, black dwarf, supergiant, supernova, neutron star, black hole
  2. A protostar is a gas and dust cloud in space that can go on to form a star
  3. Low mass stars follow the path: protostar, MS star, red giant, white then black dwarf
  4. High mass stars follow the path: protostar, MS star, red supergiant, supernova, black hole (if sufficient mass)
  5. The sun will eventually become a black dwarf
  6. A supernova is the explosion of a supergiant after it collapses
6. 7.6 How the chemical elements formed
  1. Elements as heavy as iron are formed inside stars as a result of nuclear fusion
  2. Elements heavier than iron are formed in supernovas along with lighter elements
  3. The sun and the rest of the Solar System were formed from the debris of a supernova

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	Criado por tthorne11 mais de 9 anos atrás