Karteikarten
AQA Physics Unit 2
Karten in diesem Stapel (65)
- 1What is Newton's third law?Whenever two objects interact, the forces they exert on each other are equal and opposite
- 2What is a resultant force?A number of forces acting at a point may be replaced by a single force that has the same effect on the motion as the original forces all acting together. This single force is calle dteh resultant force
- 3What effect does a resultant force have?A resultant force acting on an object may cause a change in its state of rest or motion
- 4Resultant Forces on Stationary Objects-If the resultant force is zero the object will remain stationary
-If the resultant force isn't zero the object will accelerate in the direction of the resultant force - 5Resultant Forces on a Moving Object-If the resultant force is zero the object will continue moving at the same speed in the same direction
-If the resultant force isn't zero the object will accelerate in the direction of the resultant force - 6Equation for Acceleration of an ObjectF=ma
- 7Distance Time Graph
- 8How can you find the speed of an object from a distance time graphGradient of a distance time graph is the speed
- 9Velocity Time Graph
- 10How can you calculate distance travelled and acceleration from a Velicity Time Graph?-Gradient is the accelaration
-Distance travelled is the area under the graph - 11Equation for accelarationa=(v-u)/t
- 12What are the forces acting on a vehicle travelling at a steady speed?The resistive forces (mainly air resistance) balance out the driving forces
- 13Factors affecting the Braking Force-The greater the speed of th vehicle, the greater the braking force needed to stop it in a certain distance
- 14Factors affecting stopping distanceThinking distance (distance the vehicle travels whilst the driver thinks)
-Tiredness
-Drugs
-Alcohol
-Distractions
Braking distance (distance the vehicle travels under the breaking force)
-Bad road conditions (icy roads)
-Bad weather conditions (rain)
-Bad vehicle condition (breaks and tires)
- - 15How do Brakes work?When the brakes of a vehicle are applied, work done between the brakes and the wheel reduces the kinetic energy of the vehicle so the temperature of the brakes increase
- 16Friction on a Falling ObjectThe faster an object moves through a fluid the greater the frictional force that acts on it
- 17Terminal Velocity-An object falling through a fluid will initially accelerate due to the force of gravity
-Eventually the resultant force will reach zero as the increased air resistance balances out the force of the weight of the object
-The object is then moving at terminal velocity as it cannot accelerate any more - 18Velocity Time Graph for Terminal Velocity
- 19Changing the Shape of an ObjectA force acting on an object may cause a change in the shape of the object
- 20Storing Elastic Potential EnergyA force applied to an elastic object such as a spring will result in the object streching and storing elastic potential energy
- 21Hooke's Law Graph and EquationF=ke
- 22What is work done?-When a force causes an object to move through a distance work is done
W=Fd
-Energy is transferred when work is done - 23What is Power?-Power is the work done or energy transferred in a given time
E=P/t - 24What is Gravitational Potential Energy?Gravitational Potential Energy is the energy that an object has by virtue of its position in a gravitational field
E=mgh - 25What does Kinetic Energy depend on?The kinetic energy of an object depends on its mass and speed
E=(mv^2)/2 - 26What is Momentum?Momentum is a property of moving object
P=mv - 27What is the Conservation of Momentum?In a closed system the total momentum before an event is equal to the total momentum after the event
- 28How do Objects gain Static Electricity?-When two insulating materials rub against each other they become electrically charged
-Negatively charged electrons are rubbed from off one material onto another
-The material that gains electrons becomes negatively charged
-The material that loses electrons becomes positively charged - 29How do two Electrically Charged Objects react to each other?-When two electrically charged objects are brought together they exert a force on each other
-Two objects with the same type of charge repel each other
-Two objects that carry different types of charges attract each other - 30What is Electrical Current?Electric current is a flow of electric charge. The size of the electric current is the rate of flow of electric charge
I=Q/t
Q is Charge in Coulombs - 31What is Potential Difference (Voltage)?The potential difference between two points points in an electric circuit is the energy transferred per coulomb of charge that passes between the points
V=W/Q
W is work done in Joules - 32Circuit symbols
- 33Thermistors-A temperature dependant resistor
-In hot conditions resistance drops
-In cool conditions resistance goes up
-Make useful temperature detectors - 34Light-Dependant Resistor (LDR)-LDR is a resistor that's dependant on light
-In bright light resistance falls
-In darkness resistance is high
-Used in automatic night lights and Burglar alarms - 35Current-Potential Difference Graphs-Are used to show how the current through a component varies with the potential difference across it
- 36Current-Potential Difference Graph for a resistor with a constant temperature
- 37How can you calculate resistance?-Can be found by measuring the current through and voltage across a component
-The current through a resistor (at a constant temperature) is directly proportional to the voltage across it
V=IR - 38Components Connected in Series-The total resistance is the sum of the resistance of each component
-The same current through all components
-The total potential difference of the supply is shared between the components - 39Components Connected in Parallel-The potential difference across all components is the same
-The total current through the whole circuit is the sum of the currents through the separate components - 40Resistance in a Filament Bulb-The resistance of a filament bulb increases as the temperature of the filament increases
-When an electrical charge flows through a resistor, the resistor gets hot
- 41Current Through a Diode
- 42LED Lighting-An LED emits light when current flows through it in a forward direction
-Becoming more common in lighting as they use a much smaller current than other forms of lighting - 43AC and DC Electricity-Batteries supply current that always passes in the same direction, called DC
-Mains Electricity in an ALternating Current (AC) with a frequency of 50 Hz and 230 V in the UK - 44Finding FrequencyT=1/f
f= \(\lambda\) / v - 45Structure of a 3 Pin PlugStructure of a cable is very similar, same 3 wires that are all separately insulated and then have one outer insulating cover
- 46Dealing with Electrical Faults-If an electrical fault causes too great a current, the circuit is disconnected by a fuse or circuit breaker in the live wire
-When the current in a fuse exceeds the rating of the fuse it will melt
-The thicker the cable the higher the fuse value
-Some circuits are protected by Residual Current Circuit Breakers (RCCBs)
-RCCBs work by detecting a difference in the current of neutral and live wires
-Appliances with metal casings are usually earthed
-Some appliances, however, are double insulated and so don't need to be earthed
-The earth wire and fuse both protect the wiring of the circuit - 47What is Power?The rate of energy transfer
P=E/t
P=IV - 48How are Energy, Potential Difference and Charge related?E=VQ
- 49Rutherford and Marsden Experiment-Early model of the atom said that it was a positive sphere with negative electrons in it, like plums in a plum pudding
-Fired a beam of alpha particles at a thin gold foil
-Expected them to pass through, but some came out at an angle or came straight back
-Realised they were being repelled and deflected by a concentrated centre of positive charge - 50Atomic StructureIf you really don't know what protons, neutrons, electrons, isotopes and ions are check out the C1 flashcards
- 51What are Radioactive Substances?Substances that give out radiation from the nuclei of their atoms all the time, whatever is done with them
- 52Where does Background Radiation come from?-Rocks
-Cosmic rays from space
-Fallout from nuclear weapons tests
-Fallout from nuclear accidents - 53What is Radiation made of?-Alpha particles are two protons and two neutrons
-Beta particles are one electron
-Gamma radiation is electromagnetic radiation - 54Alpha and Beta Decay-When alpha particles are emitted the nucleus loses two protons and two neutrons
-When a particle emits beta radiation a neutron in the nucleus turns into a proton - 55Properties of Alpha particles-Highly ionising
-Cannot travel far in air (eventually ionises atoms in the air)
-Not very penetrating (can be stopped by a hand) - 56Properties of Beta Particles-Moderately ionising
-Can travel moderately far in water
-Can be stopped by a few mm of aluminium - 57Properties of Gamma Particles-Not very ionising
-Can travel furthest through air
-Most penetrating, can be stopped by a few cm of lead - 58Radiation in Electric and Magnetic Fields-Alpha and Beta particles are both deflected in opposite directions
-Beta deflected more, as despite having half the charge of Alpha it has a much smaller mass
-Gamma radiation not affected as it has no charge - 59Use and Dangers of Radiation-Alpha Radiation used in smoke detectors, highly ionising but on the ceiling so far away from people
-Beta radiation used as medical tracers, as it is less ionising than Alpha
-Beta radiation also used in monitoring the thickness of materials
-Gamma radiation is used to sterilise medical equipment and treat cancer - 60Half Life-The Half Life of a radioactive isotope is the average time it takes for the count rate from a sample containing from a sample containing a radioactive isotope falls to half it's initial level
-Or the time it takes for the number of radioactive nuclei of the isotope in a sample to halve - 61What are the two fissionable substances used in nuclear reactors?-Uranium-235
-Plutonium-239 - 62Process of Fission-For fission to occur, the nuclei must first absorb a neutron
-The nucleus then splits into two smaller nuclei and 2 or 3 neutrons, energy is also released
-The neutrons may then go on to produce chain reactions
-That's why control rods made of Boron can be lowered to absorb these extra neutrons - 63Nuclear fusion-The joining of two atomic nuclei to form a larger on
-Stars use this to release energy
-Fusion in stars produces all the naturally occurring elements
-These elements are distributed throughout the universe by an exploding supernova at the end of it's life cycle - 64Life Cycle of a Star-Stars form when enough dust and gas from space is pulled together by gravitational attraction (smaller masses can also be attracted and form planets)
-During the main sequence period of it's life-cycle a star is stable because the forces are balanced
- - 65Life Cycle of a Star
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- Beschreibung
- Taken directly from the specification, so contains all you need to know for physics unit 2. Good luck for Friday =)
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- Natalia Cliff
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