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energy Flashcards

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AP® Physics flashcards Physics 101 flashcards
1
Q

what is the equation for kinetic energy?

A

1/2 x mass x velocity (squared)

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2
Q

what is the equation for elastic potential energy?

A

1/2 x spring constant x extension (squared)

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3
Q

what is the equation for gravity potential energy?

A

mass x gravitational field strength x height

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4
Q

define specific heat capacity of a substance

A

the amount of energy needed to raise the temperature of 1 kilogram of a substance by 1 degree celsius.

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5
Q

state the units for specific heat capacity

A

joules
degree celsius
kilogram

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6
Q

what is the definition of power

A

the rate at which energy is transferred
or
rate at which work is done

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7
Q

state the two equations for power

A

power = energy transferred / time
power = work done / time

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8
Q

what is the unit of power

A

watt

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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 is transferred is the same but the time taken is less

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10
Q

describe the energy changes involved when a ball is thrown upwards and then returns to tis starting position.

A

upwards: KE is converted to GPE
peak: maximum GPE, zero KE
downwards: GPE is converted to KE

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11
Q

describe the energy transfers for a bungee jumper

A
  • when falling, the GPE is converted to KE of jumper
  • as cord tightens, KE is converted and stored as elastic potential energy
  • at lowest point, the jumpers initial GPE equals the EPE stored in the cord
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12
Q

explain why a bungee jumper slows down once the cord begins to stretch

A
  • kinetic energy decreases since it is converted to elastic potential energy
  • since KE is proportional to velocity (squared), as KE decreases so does velocity
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13
Q

examples of chemical energy stores

A
  • food
  • fuel
  • batteries
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14
Q

state 4 different stores of energy

A
  1. kinetic energy
  2. gravitational potential energy
  3. elastic potential energy
  4. chemical changes
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15
Q

state the law of energy conservation

A

energy cannot be created or destroyed (it can only be transferred into different forms)

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16
Q

state the changes in the total energy of a ball that is kicked, assuming that no external forces act

A

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

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17
Q

what is waste energy

A

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

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18
Q

describe the energy changes that occur in a filament light-bulb

A
  • electrical energy is transferred into light and heat energy
  • light is a useful energy form, heat is a waste energy
19
Q

state two equations to calculate efficiency

A

efficiency = useful output energy transfer / total input energy transfer
efficiency = useful power output / total power output

20
Q

how can the efficiency of a system be increased

A
  1. reducing waste output (by lubrication or thermal insulation)
  2. recycling waste output (recycling thermal waste energy as input energy)
21
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

22
Q

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

A

lower, meaning less energy transfers through them

23
Q

what key factors affect the rate of cooling of a building

A
  1. thickness of walls
  2. thermal conductivity of the walls
24
Q

state three methods of reducing heat loss in a building

A
  1. double glazing
  2. loft and wall insulation
  3. thicker walls
25
Q

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

A

lubricate any moving parts to reuse the friction and therefore energy loss due to heating

26
Q

how can the efficiency of a radiator be improved?

A

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

27
Q

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

A

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

28
Q

what is a renewable energy resource

A

an energy source which can be used to replenish as it is being used up.

29
Q

give 4 examples of renewable energy

A
  1. wind energy
  2. hydro-energy
  3. tidal energy
  4. solar energy
30
Q

give an example of non-renewable energy

A

fossil fuels
examples are: coal/oil/gas

31
Q

what are advantages of generating power using gas rather than coal

A
  • flexible generation: gas power stations have short start-up times so can be switched off more easily and regularly
  • lower emissions of carbon dioxide
32
Q

state 2 disadvantages of renewable energy resources used to generate power

A
  • output often determined by external factors, like wind speed, so supply is not certain
  • generating power through other means is often more efficient and economically beneficial
33
Q

explain environmental impacts of burning fossil fuels

A
  • carbon dioxide contributes to the greenhouse effect, and causes global warming
  • sulphur dioxide leads to acid rain, which can damage buildings and crops
34
Q

state 3 advantages of fossil fuels as an energy resource

A
  1. reliable: not dependent on external factors so can generate power at any time
  2. can produce large amounts of energy for a given quantity
  3. still relatively abundant, so cost efficient
35
Q

state 3 advantages of nuclear power

A
  1. very large amounts of energy for relatively small quantities of fuel
  2. doesn’t release greenhouse gases so it doesn’t contribute to climate change
  3. low fuel costs
36
Q

state 3 disadvantages of nuclear power

A
  1. produces nuclear waste which is harmful to humans and must be safely stored for centuries
  2. non-renewable energy source
  3. risk of nuclear accidents, which have fatal consequences on humans and the environment
37
Q

how does hydroelectric power produce energy

A
  • rainwater collects behind a dam
  • when this water is released it is used to turn a turbine
  • this turbine turns a generator which produces electricity
38
Q

what are some disadvantages of using biofuels

A
  • when plants are burned or decay they release CO2
  • in order to grow biofuels, you need to destroy land which causes issues like destroying natural habitats, or releasing CO2
  • growing biofuels reducing land available growing for food
39
Q

what are advantages of tidal energy sources

A
  • they do not produce greenhouse gases
  • quite reliable as tides always happen twice a day
  • cheap to run as tides are natural and are free
40
Q

disadvantages of hydroelectric power

A

the dam may cause flooding
can cost a lot to install the required infrastructure

41
Q

advantages of solar panels

A
  • they don’t cause harm to the environment
  • they are renewable
  • they can be used in remote areas where other types of electricity is less available
42
Q

examples of a social factor which may act as a deterrent for certain types of energy production

A
  • visual pollution
  • sound pollution
43
Q

disadvantage of wind farms

A
  • visual pollution
  • sound pollution
44
Q
A

physics (9 decks)

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