Physics - P2
on the 90th card, GE stands for Gravitational energy and HE stands for heat energy :)
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- Created by: Ledia Luli
- Created on: 23-12-12 18:16
define gravity
the force of attraction between all masses
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define mass
the amount of 'stuff' in an object
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define weight
pull of the gravitational field on that 'stuff'
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what's the difference between weight and mass?
an object has the same mass everywhere but a different weight depending on the gravitational field strength
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what is speed?
how fast you are going with no regard to the direction
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what is weight measured in?
newtons
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what is speed?
how fast you are going with no regard to the direction
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what is velocity?
how fast you are going with the direction specified
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what is the change in velocity?
a change in speed or a change in direction or both
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mass is not a...
force
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mass is measured in...
kilograms
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define resultant force
the overall force on a point or object
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if the resultant force on a stationary object is zero..
the object will remain stationary
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if there is no reulant force on a moving object...
it'll just carry on moving at the same velocity
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if there is a non-zero resultant force...
then the object will accelerate
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reaction forces are...
equal and opposite
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when two objects interact...
the forces they exert on each other are equal and opposite
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drag increases as...
speed increases
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every object that falls through a fluid will reach...
terminal velocity
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the terminal velocity depends on...
the shape and area of the object
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what is thinking distance?
the distance the vehicle travels during the drivers reaction time
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what is braking distance?
the distance the car travels under the breaking force
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when a force moves an object through a distance...
energy is transferred and work is done
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gravitational potential energy is energy due to...
height
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conservation of energy states that energy can never be...
created or destroyed
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kinetic energy gained is equal to...
potential energy lost
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work done to an elastic object is stored as...
elastic potential energy
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extension of an elastic object is...
directly proportional to force
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when does the extention of an elastic object stop being directly proportional to the force?
when the force is great enough
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what is the limit of proportionality?
the maximum force that an elastic object can take and still extend proportionally
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what is power measured in?
watts or J/s
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momentum before is equal to...
momentum after
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in static electricity what moves?
the electrons which hold a negative charge
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changes move easily through...
conductors
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the greater the resistance across a component...
the smaller the current that flows
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define current
the flow of electric charge round a circuit
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define potential difference
the driving force that pushes the current round
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define resistance
anything in a circuit that slows the flow down
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what does the ammeter do?
it measured the current flowing through the component
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where must you place the ammeter?
in series
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what does the voltmeter do?
it measures the potential difference across the component
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where must the voltmeter be placed?
in parallel around the component under test
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resistance increases with...
temperature
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what happens in series circuits?
potential difference is shared, current is the same everywhere, resistance adds up and cell voltages add up
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what happens in parallel circuit?
potential difference is the same across all components, current is shared between branches
45 of 100
give an example of a series circuit
fairy lights
46 of 100
give an example of a parallel circuit
everything electrical in a car
47 of 100
name 9 hazards in the home
long cables, frayed cables, cables in contact with heat or water, water near sockets, shoving things into sockets, damaged plugs, too many plugs into one socket, lighting sockets without bulbs in and appliances without their covers on
48 of 100
name the three wires in a cable
earth, live and neutral wires
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what order do they go in? (from left to right)
neutral, earth then live
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what do all resistor produce when a current if flown through them?
heat
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if an appliance if efficient it...
wastes less energy
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what did John Dalton agree with in 1804?
that matter was made form tiny spheres that coudnt be broken up
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what did John Dalton propose in 1804?
that each element was made up of a different type of atom
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what did JJ Thomson discover? (it also proved John Dalton wrong)
that electrons could be removed from atoms
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what did JJ Thomson propose?
that atoms were sphers of postive charge with tiny negative electrons stuck in them like plums in plum pudding
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what experiment did Rutherford and Marsden perform?
they fired a beam of alpha particles at thing gold foil
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what did Rutherford and Marsden expect to happen?
that the positvily charged alpha particles would be slightly deflected by the electrons in the plum pudding model
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what actually happened in Rutherford and Marsden experiment?
most of the particles went straight through but the odd one came straight back at them
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what did Rutherford and Marsden conclude from their experiment?
most of the mass of the atom was concentrated at the center in a tiny nucleus, they also realise that the nucleus must have a positive charge since it repelled the positive alpha particles, it also showed that most of an atom is empty space
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what are isotopes?
different atomic forms of the same element, which have the same number of proton but a different number of neutrons
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radioactivity is a...
totally random process
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name 6 source of background radition
food, radon gas, rocks, medical x-rays, rocks and cosmic rays
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alpha particle information
it is a helium nuclei (two protons and two neutrons) they are big, heavy and slow-moving, low penetrating power
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beta particle information
they are fast (often called 'fast electrons') , medium penetrating power, for ever beta particle emitted a neuron turns into a proton in the nucleus
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gamma rays information
high penetrating power, weakly ionising, no mass or charge
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the higher the radiation odes the more at risk you are at...
developing cancer
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radiation depends on...
location and occupation
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alpha and bet particles are deflected by...
electric and magnetic fields
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gamma radiation is an...
electromagnetic wave
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the radioactivity of a sample always...
decreases over time
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define half-life
is the average time it takes for the number of nuclei in a radioactive isotope sample to halve
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what kind of radiation do smoke detectors use?
alpha radiation - a weak source of alpha radiation is put close to two electrodes, the source causes ionisation and a current flows between the electrode if there is a fire then the smoke absorbs the radiation, the current stops and the alarm sounds
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what kind radiation do tracers in medicine use?
short half-life beta or gamma-emitters
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what kind of radiation does radiotherapy use?
gamma-rays
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what kind of radiation is used in food and surgical instruments?
gamma-rays
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radiation harms...
living cells
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what kind of radiation if the most dangerous outside the body?
beta and gamma-sources, because they can penetrate the skin and get inside to delicate organs
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what kind of radiation is most dangerous inside the body?
alpha-source
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name 6 safety precautions when dealing with radiation
use the sources for as little as possible, never allow skin contact with a source, hold the source at arm's length, dont look at it and point it away from your body, wear lead protection and keep the source in a lead box
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define nuclear fission
the splitting up of a big atomic nuclei
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define nuclear fusion
the joining of small atomic nuclei
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describe the chair reaction of nuclear fission
each time a uranium or plutonium nucleus splits, it spits out two or three neutrons, which may hit another nucleus causing it to split also, thus keeping the chain reaction going
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what are the disadvantages of nuclear fission?
the waste is very hard, expensive to dispose of safely, decommissioning is also very expensive and time consuming
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what are the advantages of nuclear fission?
the fuel produced is cheap
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what are the advantages of nuclear fusion?
it produces a lot of energy,it doesn't leave behind a lot of radioative waste and there is plenty of hydrogen knocking about
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what are the disadvantages of nuclear fusion?
it only happens are really high temperatures - about 10,000,000°C, it used more energy than it produces
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what kind of container is needed for nuclear fusion?
an extremely strong magnetic field
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how is a protostar made?
the force of gravity makes the gas and dust spiral in together to form a protostar
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how is star born from a protostar?
GE is converted to HE so the temperature increases when it gets high enough hydrogen nuclei under nuclear fusion, this gives out massive amounts of heat and light
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how do planets form around the star?
smaller masses of dust and gas pull together to make planets that orbit the star
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what happens to a star in the long stable period?
the heat produces provides an outward pressure to balance the force of gravity pulling everything inwards, it maintains this for millions of years
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how long can a main sequence star last?
several billion years
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what happens when the hydrogen begins to run out?
heavier elements such as iron are made by nuclear fusion of helium, the star then swells into a red giant or a super red giant
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why is a red giant/ super giant red?
because the surface cools
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what happens to a small-to-medium star when it becomes unstable?
it ejects its outer layer of dust and gas as a planetary nebula
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what happens to the planetary nebula?
it becomes a hot, dense solid core - a white dwarf which cools down to a black dwarf then disappears
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what happens to the big stars when they become unstable?
they begin to glow brightly again as they undergo more fusion, they then expand and contract several times forming heavy elements like iron. Eventually they explode into as supernova ejecting the the iron to form other planets and stars
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what is left when the supernova explodes?
a very dense core called a neutron star or if the star is big enough a blackhole
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what are people trying to develop fusion reactor to do?
generate electricity
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Other cards in this set
Card 2
Front
define mass
Back
the amount of 'stuff' in an object
Card 3
Front
define weight
Back
Card 4
Front
what's the difference between weight and mass?
Back
Card 5
Front
what is speed?
Back
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