physics unit 2 2

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what is the resultant force on a car of mass 1000kg if its acceleration is 2m/s?
2000N
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what is the resultant force on a car travelling at a steady speed on a straight horizintal road
zero
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what is the relationship between shopping distance, thinking distance and breaking distance?
stopping distance = thinking distance and breaking distance
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why does an object dropped in a fluid initially accelerate?
there is a resultant force acting on it
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what eventually happens to an object falling in fluid?
it will reach terminal velocity because the resultant force become zero
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what is an inelastic object?
an inelastic object is one that does not regain it original shape when forces deforming it are removed
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a spring has a spring constant of 30N/M. if the extension is 0.30m what is the force applied?
9N
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how can we tell when a spring has exceeded its limit of proportionality?
the graph of extension to force applied is no longer a straight line
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why does making a vehicle more streamlined improve fuel economy?
less engine force and less power is needed to maintain a certain speed, less fuel is needed so fuel costs are reduced
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when a vehicle is travelling along straight road at a steady speed what can you say about the engine force and the air resistance?
the vehicle is not accelerating, so the resultant force on it is zero. so the engine force and air resistance are balanced
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what is the unit of work done?
joule, J
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what is the work done on an object if a force of 300N moves it a distance of 8m?
2400J
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what is the increase in gravitational potential, when a mass of 40kg is lifted 8m vertically?
320J
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it takes 2 seconds to lift an object of 40kg 8m vertically. what is the power developed?
160W
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a boy of mass 40kg runs at the speed of 5m/s. what is his kinetic energy?
500J
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when a spring is squashed and released it warms up. why
some of the elastic potential energy is transferred by heating
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when do objects have momentum?
when they are moving
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what is the momentum of a 100kg car travelling at 30m/s?
30000kg m/s
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what is the total momentum after an explosion equal to?
the total momentum before the explosion
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what is impact time?
time taken for a collision to take place
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why do cars have crumple zones at both the front and the rear?
car may be hit from both ends of the car, in both cases the crumple zone reduces the forces on the car and increase the impact time
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what happens to a passenger in a head in collision: (a( if theyre not wearing a seat belt (b) if they were wearing a very narrow seat belt?
(a)they continue to move forward when the car stops and will hit the windscreen (b) the narrow seat belt would not spread the forces across the passengers body and will cut them.
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how does an illustrator become negatively charged?
it gains electrons
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what will happen if 2 negatively charged objects are brought close together?
they will repel eachother
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what is the circuit symbol for a closed switch?
----*/*----
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what device is used to measure current?
an ammeter
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what is the unit of resistance?
ohms
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what happens to the resistance of an LDR if its surroundings become darker?
the resistance of the LDR increases
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what effect does reversing the potential difference across a filament bulb have on the current-potential difference curve on a graph?
reversing the PD has no effect on the current-PD curve for a filament bulb
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what happens in a series circuit if one component stops working?
there is no complete path for the current so no current/electricity flows
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how could you find the total resistance in a series circuit?
add all the individual resistances
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what happens in a parallel circuit if one component stops working?
current can not flow though that component but can flow though other parts of the circuit
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what is direct current?
current passes in one direction only
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what is the potential of the neutral terminal?
0V
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why are the pins of a plug made of brass?
brass is a good conductor, and doesn't rust or oxidise
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why must appliances with metal cases be earthed?
so the case cannot become live and electrocute you
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what is a fuse?
a thin wire that heats up and melts if too much current is passed through it
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why don't appliances with plastic casing need to be earthed?
plastic is a insulator so cannot become live and electrocute you
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what is the power of a main appliance that takes a current of 10A?
2300W
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how much charge flows past a particular point in a circuit when a current of 2A flows for 2 minutes?
240C
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why can 2 core cables b used for a hair dryer?
the case of the hair dryer is plastics so it doesn't a earth wire
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why are filament bulb very insufficient?
they transfer a lot of energy by heating than light
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which part of an atom emits alpha particles?
the nucleus
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what happens to the rate of radioactive decay if the temperature is doubled?
its stays the same
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why is most the alpha particles pass straight through the foil in Rutherford's experiment?
because most the atom is empty space
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what did the alpha particle scattering experiment suggest about the structure of the nucleus?
the nucleus is where most the mass of the atom is concentrated, very small and positively charged
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what is the relative charge of an alpha particle?
+2
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what is the relative charge of a beta particle?
-1
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which type of nuclear radiation is the least penetrating?
alpha
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which type of nuclear radiation is the least ionising?
gamma
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what happens to the count rate of a radioactive sample over time?
it desreases
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what has happened to the original count rate of a radioactive sample after two half-lives have passed?
it has decreased to a quarter of its original value
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why isnt an alpha source used as a tracer in medicine?
alpha particles are poorly penetrating, so they wouldn't be detected outside the body. alpha is also very ionising so would be very damaging for the patient
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why do medical tracers have half-lives of a few hours?
to allow time to complete the procedure but minimise unnecessary exposure of the patient
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what is enriched uranium?
uranium that contain 2-3% uranium-235
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what happens of fission to occur?
a nucleus absorbs a nuetron
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by what process is energy released in stars?
fusion
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how are nuclei contained in a fusion reactor?
in a magnetic field?
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what is the major source of background raidiation?
radon gas
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why must radioactive wast be stored securely?
so that is does not enter the environment as it is still radioactive and dangerous
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what happened to the temperature of the universe as it expanded?
it decreased
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what is a galaxy?
a collection of billions of stars held together by their own gravity
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why are main sequence stars stable?
the forces acting on them are balanced
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what is a neutron star?
the core left after a supernova explodes
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what is the heaviest element formed by fusion in a main sequence star?
iron
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how are chemical elements distributed through space?
by a supernova explosion
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Card 2

Front

what is the resultant force on a car travelling at a steady speed on a straight horizintal road

Back

zero

Card 3

Front

what is the relationship between shopping distance, thinking distance and breaking distance?

Back

Preview of the front of card 3

Card 4

Front

why does an object dropped in a fluid initially accelerate?

Back

Preview of the front of card 4

Card 5

Front

what eventually happens to an object falling in fluid?

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