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Physics > P1 > Flashcards

P1 Flashcards

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Physics 101 flashcards AP® Physics flashcards
1
Q

examples of energy stores?

A 
thermal
KE
GPE
EPE
Chemical
Magnetic
Electrostatic
Nuclear
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2
Q

how is energy transferred mechanically

A

by a force doing work

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3
Q

how is energy transferred electrically

A

by moving charges

ions/delocalised electrons

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4
Q

how is energy transferred by heating/radiation

A

by light or sound

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5
Q

what’s a system

A

an object or group of objects

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6
Q

what happens when the system changes

A

energy is transferred into or away from the system, between different objects or different types of energy stores

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7
Q

what’s a closed system

A

system where matter or energy can’t leave

net change of total energy is always 0

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8
Q

explain the energy transfer by heating in a kettle

A

energy is transferred to water (from kettle heating agent) by heating into the thermal energy store
temp. increases

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9
Q

define work done

A

another way of saying energy transferred

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10
Q

how can work be done

A

when a current flows

or by a force moving an object

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11
Q

explain how work is done when a ball is thrown upwards

A

initial force exerted by person to throw ball up does work

energy transfer from chemical energy store to KE energy store of the ball and arm

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12
Q

explain how work is done when a ball is dropped from a height

A

ball dropped from a height is accelerated by gravity- the force does work
causes energy ti transfer from ball’s GPE to KE store

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13
Q

explain how work is done when an object slows down (car)

A

friction between car’s brakes and its wheels does work as it slows down
energy transfer from wheels’ KE store to thermal store of surroundings

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14
Q

explain how work is done when a moving object (car) hits an obstacle/stationary object

A

when they collide, normal contact force does work
energy transfers from car’s KE tore to other stores e.g. elastic/thermal of obstacle and car body
some energy transferred as sound waves

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15
Q

what’s the KE equation?

A

KE = ½ x m x v²
(mass in kg)
(energy in J)
(speed in (m/s)²)

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16
Q

what’s the GPE equation?

A 
GPE = m x g  x h
(energy in J)
(mass in kg)
(GFS in N/kg)
(height in metres)
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17
Q

what’s the rule when there’s a falling object with no air resistance?

A

energy lost from GPE store = energy gained in KE store

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18
Q

what’s the EPE equation?

A

EPE = ½ x k x e²
(energy in J)
(spring constant in N/m)
(extension in metres)

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19
Q

what’s SHC

A

amount of energy needed to raise the temp. of 1kg of a substance by 1°C

20
Q

what’s the SHC equation?

A 
ΔE = m x c x ΔT
(energy in J)
(mass in kg)
(SHC in J/kg°C)
(temp. in °C)
21
Q

explain SHC practical

A

1) get a block of a material (copper)
2) put 2 holes in it for heater and thermometer
3) measure block mass
4) wrap block in insulation layer to reduce energy transfer to surroundings
5) insert thermometer and heater
6) measure initial temp of block
7) set p.d. to 10V, turn on power supply and stop watch
8) current in circuit does work on heater, so energy electrically transferred from from power supply to heater’s thermal store by heating so temp increases
9) take readings every min for 10 mins, current doesnt change
10) after 10 readings calc power supplied and energy transfer to heater

22
Q

define the term power

A

the rate at which energy is transferred/work is done

23
Q

which equation links power and energy/work done?

A

power (Watts) = energy transferred OR work done (J)
——————————————————
time (secs)

24
Q

how many Watts is 1 Joule per second?

A

1 Watt

25
Q

what equation links power, current and voltage

A

Power = Current x Voltage

26
Q

what’s the conservation of energy rule?

A

energy can be transferred usefully, stored or dissipated, but can never be created or destroyed

27
Q

what happens to waste energy

A

it’s dissipated so it’s stored in less useful ways

28
Q

how can unwanted energy transfers be reduced?

A

lubrication to reduce friction->liquids/oils

insulation to reduce transfer by heating->thermal insulation (double-glazed windows)

29
Q

how is energy dissipated in a mobile phone?

A

energy is transferred from chemical store in battery

but some energy is dissipated during the transfer to the thermal store of the phone, so its temp. increases

30
Q

how is energy dissipated in a closed system e.g. spoon in soup?

A

cold spoon dropped into sealed insulated flask of hot soup
flask is a perfect thermal insulator so a closed system is formed
energy transferred from thermal store of soup to useless thermal store of spoon, soup cools down
energy transfer occurred but none left the system so net energy change is 0

31
Q

what can a powerful machine do? (a machine with high power)

A

transfer a lot of energy in a short amount of time

power = energy / time

32
Q

what’s the link between thermal conductivity and energy transfer?

A

the higher the thermal conductivity of a material the higher the rate of
energy transfer by conduction across the material

33
Q

how do walls affect the cooling of a building?

A

thick walls made of low thermal conductivity material

the thicker the walls and the lower their thermal conductivity, the slower the rate of energy transfer -> cools slower

34
Q

what’s conduction

A

process by which vibrating particles transfer energy to neighbouring particles (ONLY SOLIDS)

35
Q

what’s convection

A

where energetic particles move away from hotter to cooler regions (ONLY LIQUIDS AND GASES)

36
Q

what’s a convection current

A

warmer/less dense region rises over cooler/more dense regions
if there’s a constant heat source it rpeats

37
Q

how do radiators create convection currents?

A

1) energy transferred from radiator to nearby air particles by conduction
2) air near radiator gets warmer/less dense and moves quicker (more KE)
3) warm air rises and is replaced by cooler air
4) cooler air is heated
5) previously heated air transfers energy to surroundings, cools/becomes less dense and sinks
6) cycle repeats

38
Q

PAG: investigate effectiveness of different materials as thermal insulators

A

1) boil water in kettle and pour some into sealable container at a safe level
2) measure volume of water in container
3) use thermometer to measure initial temp
4) seal and leave for 5 mins with stopwatch
5) measure final temp. pour away water, let container cool to room temp.
6) repeat with same water volume with different materials with different thickness
7) the lower the temp. difference, the better the thermal insulator

39
Q

what’s the efficiency equation?

A

efficiency = useful output / total input

40
Q

why is useful energy input not always equal to total energy output?

A

no device is 100% efficient

energy can be dissipated as waste

41
Q

define a renewable energy resource

A

a resource that’s being (or can be) replenished

as it’s being used

42
Q

non-renewable energy sources

A 
fossil fuels (coal, oil, natural gas)
nuclear fuel
43
Q

examples of renewable sources

A 
solar
wind
hydro-electric
bio-fuel
tides
geothermal
water waves
44
Q

what are the main energy resources available for use on Earth?

A 
fossil fuels (coal, oil and gas)
nuclear fuel
biofuel
wind
hydro-electricity
geothermal
tides
the sun
water waves
45
Q

state some uses of energy resources

A

transport
electricity
generation
heating

Physics (9 decks)

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