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Physics year 10 > Energy > Flashcards

Energy Flashcards

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1
Q

what is a system?

A

single/group of objects

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2
Q

what are closed systems?

A
  • matter/energy can’t leave
  • net change in total energy = 0
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3
Q

explain the energy transfer of boiling water (system) in a kettle

A
  • energy is transferred to water from heating element
  • by heating
  • then into water’s thermal energy store
  • temp rise
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4
Q

explain the energy transfer of boiling water in a kettle (two-object system)

A
  • energy transferred electrically
  • to heating element’s thermal energy store
  • transfers energy by heating water’s thermal energy store
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5
Q

the initial force exerted by a person to throw a ball upwards does work

A
  • energy transfer from chemical energy store of arm
  • kinetic energy store of ball and arm
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6
Q

a ball dropped from a height is acceleratedby gravity. the gravitational force does work.

A
  • energy transferred from ball’s gpe store
  • to kinetic energy store
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7
Q

the friction between a car’s brakes and its wheels does work as it slows down.

A
  • energy transfer from wheels’ kinetic energy stores
  • to thermal energy store of surroundings
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8
Q

in a collision between a car and a stationary object, the normal contact force between the car and the object does work.

A
  • energy transferred from car’s kinetic energy store to other stores
  • e.g. elasic potential and thermal energy stores of object and car body
  • some transferred away by sound waves
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9
Q

for a falling object where there’s no air resistance

A

energy lost from gpe store = energy gained in the kinetic energy store

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10
Q

equation for kinetic energy

A

Ek= 1/2 m v2

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11
Q

what is velocity measured in?

A

m/s

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12
Q

equation for gpe

A

Ep= m g h

(mass x gravitational field strength x height)

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13
Q

what is gravitational field strength measured in?

A

N/kg

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14
Q

equation for elastic potential energy

A

Ee= 1/2 k e2

(1/2 x spring constant x extension2)

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15
Q

what is the spring constant measured in?

A

N/m

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16
Q

what is the extension measured in?

A

meters

17
Q

what is specific heat capacity?

A

amount if energy needed to raise temp of 1kg of substance by 1ºC

18
Q

equation linking energy transferred to specific heat capacity

A

△E= m c △Ø

(change in thermal energy energy = mass x specific heat capacity x temp change)

19
Q

what is specific heat capacity measured in?

A

J/kgºC

20
Q

how can you set up an investigation on the specific heat capacity of a solid material with two holes?

A
  1. measure mass then wrap in insulator
  2. insert thermometer and heater
  3. measure initial temp and set pd of power supply to 10V
  4. turn on power supply and stopwatch
21
Q

how can you commence an investigation of the specific heat capacity of a solid material with two holes in it?

A
  1. turn on power: energy transferred electrically from power supply to heater’s thermal energy store to material by heating
  2. as temp rises, measure it and current every minute for 10 mins
  3. turn off power supply
  4. use P=IV and then E=Pt
22
Q

why do we insulate the solid block with a thick layer of newspaper when investigating the specific heat capacity of it?

A

reduce energy transferred to surroundings

23
Q

how do you find the gradient of a graph of energy transferred when trying to find the specific heat capacity?

A
  • △Ø / △E
  • 1 divided by (gradient x mass of block)
24
Q

what is dissapated energy?

A

wasted energy

25
Q

what is the useful and sissipated energy of a mobile phone (system)?

A
  • useful energy transferred to chemical store of battery
  • energy dissipated when transferred to thermal energy store
26
Q

a cold spoon dropped into an insulated flask of hot soup which is then sealed (closed system)

A
  • energy transferred from soup’s thermal energy store
  • spoon’s useless thermal energy store
  • soup cools slightly
  • energy transferred within system = no energy left
  • net change in energy = 0
27
Q

what is conduction?

A

vibrating particels transfers energy to neighbouring particles

28
Q

what is convection?

A
  • energetic particles move away from hotter to cooler regions
  • only in liquids and gases
29
Q

what happens when you heat a region of a gas or liquid?

A
  • partciles move faster
  • space between particles increase
  • density decreases
  • flow: warmer, less dense region rises above cooler, more dense
30
Q

how does convection currents occur?

A

-constant heat source

31
Q

heating a room with a radiator relies on creating convection currents in the iar of the room

A
  • energy transferred from radiator to nearby air particles by conduction
  • air becomes warmer, less dense as particles move more quicker
  • warm air rises, replaced by cool air heated again
  • previously heated air transfers energy to surroundings
  • cools, becomes denser and sinks
  • cycle repeats
32
Q

how does air resistance cause energy to be dissipated?

A
  • transfer energy to falling object’s kinetic energy store
  • to thermal energy store
33
Q

how can you investigate the effectiveness of materials as thermal insulators?

A
  • boil water and pour into sealable container to safe level
  • measure mass
  • use thermometer measure initial temp
  • seal and leave for 5 mins using stopwatch
  • remove lid and measure final temp

pour water away and cool container to room temp

-repeat using different materials as insulators

34
Q

what can you conclude from an investigation of the effectiveness of materials as thermal insulators?

A

-lower temp difference = better that material as thermal insulator

35
Q

three main fossil fuels

A
  • coal
  • oil
  • gas
36
Q

expand on the non-renewable energy resources

A
  • all run out one day
  • all damage environment
  • provide most of our energy
37
Q

expand on the renewable energy resources

A
  • renewed won’t run out
  • less damage to environment
  • don’t provide as much energy
  • unreliable: depends on weather
38
Q

7 renewable energy resources

A
  1. solar
  2. wind
  3. waterwaves
  4. hydro-electricity
  5. bio-fuel
  6. tides
  7. geothermal

Physics year 10 (6 decks)

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