Flashcards
Physics 2
Flashcards do conjunto (124)
- 1Definition of velocity?Speed in a given direction.
- 2Distance-time graph features...Gradient=Speed
Flat=stopped
Straight line=steady speed
Steep=fast
Downhill=going back to start
Curves=acceleration or deceleration
Steepening curve=speeding up - 3What is a time graph measured in and how is it worked out?In m/s
Speed=gradient
=vertical/horizontal
S
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DxT - 4What is velocity and acceleration measured on?m/s2
- 5how is Acceleration measured?change in velocity
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Time taken
V-U(final velocity-initial velocity)
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AxT - 6Velocity time graph features...Gradient=Acceleration
Flat sections=Steady speed
Steeper=Greater acceleration or deceleration
Uphill=Acceleration
Downhill=Deceleration
Curve=Change in acceleration - 7Definition of weight?The mass times gravitational pull?
- 8Formula for working weight, gravity and mass?weight=mass x gravitational field strength
- 9What is mass measured in? What is weight measured in?Kg
Newtons - 10Definition of resultant force?Is the overall force on a point or object.
- 11There are usually 2 forces acting on an object which force will decided where it moves, and what is the force called?We biggest one biggest minus the smallest=size of force and direction, resultant force.
- 12If there's no resultant force on a moving object?object stays the same velocity and stay same speed
- 13If there is a non-zero resultant force, than the object will?accelerate or decelerate in the direction of the force.
- 14Overall resultant force means?acceleration
- 15resultant force formularesultant force(n)
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mass(kg) x acceleration(m/s2) - 16when two objects interact, the forces they exert on each other are...equal and opposite
- 17resistance or drag from fluids (air or liquid) (air resistance).
- 18Drag increases as the...speed increses
- 19Definition of terminal velocity?When something falls to the ground it speeds up to certain point then the frictional force increases so it becomes a steady speed.
- 20What effects terminal velocity speed?Area, shape, weight
- 21factors affecting total stopping distances?Speed
Friction - 22What is thinking distances and how is it affected?How long it takes you to react to brake, tiredness,drugs, alcohol, careless.
- 23what is Braking distance?When you first brake and the distance it takes to stop.
- 24When a force moves an object through a distance Energy is Transferd and...and work is done
- 25Formula for work?work done
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force x distance - 26Gravitational potential energy is...Energy due to height.
- 27Gravitational potential energy formula...G(joules) =mass x g(distance) x height
- 28Kinetic energy formula?1/2 x mass x speed2
- 29Energy transferred is...work done
- 30kinetic energy transferred= work done1/2mv2=f x d
- 31Kinetic energy gained=potential energy lost
- 32Work done to an Elastic object is stored asElastic potential energy
- 33Extension of an elastic object is directly proportionalto force
- 34formula for powerpower= work done(energy transferred
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time taken - 35Formula for momentummomentum=mass x velocity
- 36momentum before=momentum after
- 37What does postive mean in moments?To the right
- 38What happens when a force acts on a object?It causes a change in momentum
- 39What does a large force mean on momentum?Faster change in momentum (greater acceleration)
- 40If momentum changes quickly what happens to force?Forces large on the object.
- 41How to work out momentum before collision?Momentum of person/object + momentum of other person/object
- 42What does regenerative brakes do?Rather than converting kinetic energy into heat energy. Motor goes into reverse, and motor acts as an electric generator.
- 43Cars are designed to convert kinetic energy safely in a crash how?By increasing the time over which momentum changes happen, which lessens the forces on the passengers.
- 44What are the design features?Crumple zones,
Sieve impact bars,
Seat belts,
Air bags. - 45Build up of static is caused by?Friction
- 46What happens when insulating material gets rubbed together?Negative electrons scrapped off or dumped
- 47What charge is left on the insulating material?Negative on one, positive on other static charge
- 48Which way electrons are transferred depends on what?Two materials involved.
- 49Electrostatic charges are produced byElectron movement and positive charges don't move.
- 50Opposites attracted and sameRepel.
- 51What is current?Flow of electric charge round the circuit. Current will only flow through a component if there is a potential difference across that component. Unit ampere
- 52What is Potential difference?Is the driving force that pushes the current round unit volt
- 53What is resistance?Is anything in the circuit which slows down the flow.
Unit ohm - 54The greater the resistance across a component,The smaller the current that flows (for a given potential difference across the component)
- 55Total charge through a circuit depends on?Current and time
- 56Formula for current?Current= charge
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Time - 57Potential difference is theWork done per unit charge
- 58Formula for potential difference?Work done
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Charge - 59What does the Ammeter do? Where should it be placed in the circuit?Measures current,
Must be placed in series. - 60What does the voltmeter do? Where should the voltmeter be placed in the circuit?Measures the potential difference.
Must be placed in parallel only around the component. - 61Different resistors graph.Straight line through centre and different angles.
- 62Filament lamp graph look like.Curve through the centre like an S!
As the temp increase the resistances increases. - 63Diode graph look like.Straight on x axis Darry's on a bit after Y and curves up.
Diode in one direction,
Diode has very high resistance in the opposite direction. - 64Resistances increases with temperature because....It gets hot,causing the ions in the conductor to vibrate more making it harder for them to be carried in the current.
- 65Problems of a series?One component disconnected circuit broken.
- 66What are the features of a series?Potential difference shared so it always adds up to source voltage.
Current is the same everywhere.
Resistances adds up.
Cell voltages add up. - 67What is a parallel circuit?Each is separately connected and If you disconnect a component it doesn't effect the rest.
- 68Features of parallel circuit?Potential difference is the same across all components.
Current is shared between branches.
Voltmeters and ammeter are exceptions. - 69What is AC?Mains supply
Alternating current - 70What is DCBattery supply
Direct current - 71What is the uk mains supply?230 volts
- 72Oscilloscope shows electricity supply. What does the trace look like for AC and DC?AC is up and down wavy line
DC straight line - 73How to read an oscilloscope trace?From top of frequency gap between the too = time period
- 74What are hazards of electricity?Long cable,
Frayed cable,
In contact with water,
Putting things in sockets,
Damaged plug,
Too many plugs,
Light without bulb - 75What is the brow wire in a plug?Live wire which alternates between high +ve and -ve voltage
- 76What is the blue wire in a plug?Neutral wire
- 77Green and yellow wire?Earth wire is for protecting the wiring, and for safety- prevents shocks. It is attached to the metal casing of the plug and carries the electricity to earth.
- 78What causes a fault?Live wire touching metal case
- 79What happens to stop people being electrocuted when a fault occurs?Case is earthed, too great a current flows in through the live wire through the case and out the earth wire.
- 80What does this surge of elec do?Melts fuse do trips circuit breaker in live wire because when current is greater than the fuse rating. This cuts off the live supply and breaks the circuit.
- 81Disadvantages, Advantages of circuit breakers over fuses?Protects circuit from damage,
Break by opening a switch,
More convent as reset by switch not replaced,
More expensive - 82Why are filament bulbs less effiecent?Wasted energy as heat
- 83Fuse size is worked out by amount of current, power formula =Current x potential difference
- 84What is the plum pudding theory?That atoms are spheres of positive charges with tiny negative electrons stuck to them
- 85Why was this theory proved wrong?A beam of Alpha particle was fired at a thin gold foil. They expected that the positive Alpha charge would be deflected. But most when straight through
- 86What did they conclude from the experiment?Atoms are positive charged with a con treated centre of a tiny nucleus. And mostly empty space.
- 87Proton mass and charge?1.
+1 - 88Neutron mass and charge?1
0 - 89Electron mass and charge?1/2000
-1 - 90What are isotopes?With the same number of protons but different neutrons.
Same atomic number but different mass - 91Radio activity decay is a complete random action can you stop it?No
- 92What back ground radiations are there?Air, food, building material, rocks. Natural occurrence!
Space
Man made - 93What are alpha particles mad of?Helium nuclei- 2 neutrons and 2 protons.
- 94Properties of alpha particles?Big so don't penetrate very far in materials even when travelling through air, so stopped quickly.
Strongly ionising- meaning they bash into a lot of atoms and knock electrons off them - 95What are beta particles?Electrons
- 96Properties off beta particles?Quite fast and they small.
Penetrate moderately into materials before colliding and moderately ionising.
For every BP emitted, a neutron turns to a proton in nucleus.
No mass and charge -1 - 97What does uranium-238 turn into?Thorium-234
- 98What does carbon-14 turn into?Nitrogen-14
- 99What are gamma rays made of?Very short wavelength EM Waves.
- 100Properties of gamma?Penetrate far into materials and pass straight through air.
Weak ionising
No mass or charge - 101What does radiation does depend on?Location and occupation.
- 102What places are most likely to increase your exposure.Radioactive rocks under houses, nuclear industry workers are more exposed, radiographers, pilots, underground workers
- 103Alpha and beta particles are deflected by what?Electric and magnetic fields
- 104What directions do the particles get deflected in?Opposite as they are oppositely charged.
Alpha deflected less as it has a higher mass - 105Radioactivity does what over time?Decreases
- 106What is half life?Average time it takes for the number of nuclei in a radioactive isotope sample to halve
- 107How to work out half life? E.g radioisotope is 640 cpm and has fallen to 80 cpm in 2 hours640/2 = 1 half life 320
320/2= 2 half life 160
120/2= 3 half life 80
So work out how much the half life takes by doing 120 mins (2hours)/ 3 (half life's) = 40 mins - 108Uses of radiation?Smoke dector,
Medicine,
Radiotherapy,
Sterlastion - 109How does a smoke dector work?Smoke is absorbed by faction of alpha and current stops and alarms sound
- 110How is it used in medicine?Injection or tablet for scan to show where most is being absorbed to show if that part is working correctly.
Only gamma and beta are used? - 111Radiotherapy?To kill cancer cells
- 112Advantages of sterilisation?Lower temps then boiling so food or material isn't damaged.
Last longer.
No radioactive is left in food do safe. - 113Outside the body beta is most dangerous.Inside the body alpha is most dangerous
- 114What is Nuclear fission?Splitting up of big atomic nuclei
- 115How does a nuclear power station work?Controlled chain reaction, atomic nuclei split up and release energy in heat, heating water. The fuel used is usually uranium 235 or plutonium-239
- 116What is nuclear fusion?Joining of small atomic nuclei.
- 117Advantages of fusion?More energy release,
Less wage,
Lots of hydrogen to do it. - 118Disadvantages of fusion?High temp to do,
Need special container for this with hydrogen so more expensive - 119How to stars began?Clouds of dust and gas - gravity causes them to spiral together to become a protostar.
- 1202nd step a star takes.Graviton all energy converted to heat energy. Hydrogen nuclei do nuclear fusion to form helium nuclei which five out heat and light.
- 121Stage 3 for star? Main sequence star.In a long stable period- heat from fusion give outward pressure to balance force of gravity pulling inwards.
- 122Stage 4?Hydrogen runs out, heavy elements such as iron made by nuclear fusion of helium. Then swells. Small red giant, big red super giant.
- 123What next for a red giant?Ejects outer layer of dust and gas as a planterary nebula. Which leaves behind a white dwarf, which cools to a black dwarf then disappears.
- 124What happens to a red super giant?Began to go under more fusion and expand and contract and eventually explode as a supernova ejecting elements heavier then iron to make new planets and stars. What's left is a neutron star which can become a black hole.
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- FlashCards sobre Physics 2, criado por Molly Turvey em 06-04-2014.
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- Molly Turvey
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