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aqa gcse physics > topic 1 : energy > Flashcards

topic 1 : energy Flashcards

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1
Q

what is the equation for kinetic energy give si units for all quantities involved ?

A

EK = 1/2 mv ( squared)
kinetic energy= 1/2 mass x velocity (squared)

enrgy (j) mass(kg) velocity (m/s)

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2
Q

what is the equation for elastic potential energy, give si units for all quantities involved ?

A

Ee = 1/2 k e (squared)
elastic potential energy= 1/2 spring constant x ( extension squared)
energy (j) spring constant(n/m) extension (m)

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3
Q

what is the equation for gravitational potential energy ,? give si units for all quantities involved

A

Ep=mgh
gravitational potential energy= mass x gravitational field strength x height
energy(j) mass(kg) gravitational fieldstrength (n/kg) height(m)

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4
Q

define the “ specific heat capacity “ of a substance

A

the amount of energy required to raise the temperature of 1kg of a substance by 1 degrees

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5
Q

state the units for specific heat capacity

A

j/ degrees celcius / kilo gram (kg)

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6
Q

what is the definition of power ?

A

the rate at which energy is transffered

the rate at which work is done

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7
Q

state two equations for power give si units for all quantities involved

A 
power= energy transfered / time 
power = work done / time
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8
Q

what is the unit of power ?

A

watt (w)

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9
Q

two motors lift the same mass through the same height, motor A does this in half the time of motor B. Which dissipates the most power ?

A

Motor A

the energy transffered is the same but the time taken is less P= E/t

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10
Q

describe the energy changes involved when a ball is thrown upwards and then returns to its starting position ? ( ignore air resistance )

A

> upwards kinetic too gpe
peack maximum gpe no kinetic energy
downwards gpe too kinetic

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11
Q

describe the enrgy transfers for a bungee jumper

A 
> falling gpe too Ke 
>chord tightens Ke too Epe
> rope fully stretched zero kinetic too all energy in elastic store 
> rope recoils elastic too kinetic 
> during ascent kinetic too gpe 
> top of ascent all energy in gpe store
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12
Q

explain why the bungee jumper slows down once the chord begins to stretch

A

> kinetic energy decreases since its converted to elastic potential energy
since Ke is proportional to ( velocity squared ) as the kinetic energy decreases so does speed

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13
Q

the bungee jumper never returns back to its original position , why is that ?

A

energy is dissipated as thermal energy
> friction with the air particles
> stretching effects in the bungee rope ( which is not full elastic)

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14
Q

give examples of chemical energy stores

A

food, fuel ( wood coal petrol), batteries

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15
Q

state four different stores of energy

A

1 kinetic energy
2 gravitational potential energy
3 elastic potential energy
4 chemical energy

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16
Q

state the law of conservation of energy

A

energy can be transffered usefully, stored or dissipated but cant be created or destroyed

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17
Q

state any changes in the total enrgy of a ball that is kicked assuming that no eternal forces act

A

the total energy of the system remains constant due to the conservation of energy

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18
Q

what is waste energy ?

A

the energy that is not used by the device for its desired purpose

19
Q

describe the energy changes that occur in a filament light bulb

A

> electrical energy too light + thermal energy

> light energy is the useful energy form , thermal is wasted

20
Q

state two equations to calculate efficiency

A

1 useful output energy transfer/ total input energy transfer

2 useful power output / total power input

21
Q

how can the efficiency of a system be increase ?

A

1 reducing watse output ( lubrication or thermal insulation)

2 recycling waste output ( recycling thermal waste energy as input energy )

22
Q

state the consequence for energy transfer of a material with a high thermal conductivity

A

the rate of energy transfer through the material is higher than for a material with a lower thermal conductivity

23
Q

do double glazed windows have a higher or lower thermal conductivity than single glazed windows ?

A

lower reducing energy transfers through them

24
Q

what key factors effect the rate of cooling of a building ?

A

> the thickness of the walls

> the thermal conductivity of the walls

25
Q

state three methods of reducing heat loss through a building

A

> loft insulation
double glazed windows
thicker walls

26
Q

how can the efficiency of a mechanical machine with moving parts be inproved ?

A

lubricate any moving parts to reduce friction and therefore energy loss due too heating

27
Q

how can the efficiency of a radiator be improved ?

A

installing metal foil sheets behind the radiator to reflect heat back into the room rather than it being absorbed into the walls

28
Q

how can the efficiency of boiling water in a pan be improved ?

A

by placing a lid on the pan to reduce heat loss from the top

29
Q

what is a renewable enrgy resource

A

an energy resource that can be replenished at the same rate its being used up

30
Q

give four examples of renewable energy resources

A

1 solar energy
2 wind energy
3 tidal energy
hydro-electric energy

31
Q

give an example of a non renewable energy resource

A

fossil fuels ( coal, oil ,gas )

32
Q

what are the advantages of generating power using gas rather than coal

A

flexible generation: gas power stations have a short start up time ( can be switched on/ off more readily)
lower emmisions of carbon dioxide

33
Q

state two disadvantages of using renewable energy resources to generate power

A

1 output is often determined by factors such as windspeed so supply is uncertain
2 generating power through other means isoften more efficient and economically beneficial

34
Q

explain the environmental inpacts of burning fossil fuels

A

> carbon dioxide contributes to green house effect and causes global warming
sulphur dioxide leads to acid rain which can damage buildings and crops

35
Q

state three advantages of using fossil fuels as an energy resource

A

1 reliable = not dependant on external factors so can produce power anytime
2 can produce large amounts of energy for a given quantity
3 still relatively abundant so cost effective

36
Q

state three advantages of nuclear power

A

1very large amount of energy produced from relatively low amount of fuel
2 doesnt release greenhouse gases so doesnt contribute to climate change
3 low fuel costs

37
Q

state three disadvantages of nuclear power

A

1 releases radioactive waste, harmfull to humans must be stored for centuries
2 non renewable
3 risk of nuclear accidents , fatal consequences on humans and environment

38
Q

how does hydroelectric power produce energy ?

A

> rainwater collects behind a dam
water is released and used to turn a turbine
turbine turns a generator which produces electrisity

39
Q

what are some disadvantages of using biofuels ?

A

> when plants are burned/ decay they release carbon dioxide
growing biofuels reduces land available for growing food
in order to grow biofuels you need to destroy land , this leads to problems because
- land could have been natiral habitats
- destroying land may involve burning plants growing on it which would release carbon dioxide

40
Q

what are the advantages of tidal energy sources ?

A

> no green house gases
quite reliable, tides happen twice a day
cheap to run, tides are natural so are free

41
Q

what are the disadvantages of hydroelectric power ?

A

> dam may cause flooding

> can cost alot to install required infrastructure

42
Q

what are some advantages of solar panels ?

A

> dont cause harm to environment

> can be used in remote areas where other types of energy are less accessible

43
Q

give examples of social factors which may act as a dererant for certain types of energy production

A

> visual pollution
sound pollution
( both of these are disadvantages of wind farms )

aqa gcse physics (1 decks)

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