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physics > energy ✓ > Flashcards

energy ✓ Flashcards

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AP® Physics flashcards Physics 101 flashcards
1
Q

what is energy measured in ?

A

Joules (J)

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2
Q

what is power measured in ?

A

Watts (W)

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3
Q

what are Watts equivalent to ?

A

Joules per second (J/s)

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4
Q

can energy be created ?

A

no

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5
Q

can energy be destroyed ?

A

no

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6
Q

can energy be transformed ?

A

yes

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7
Q

what can energy be transformed into ?

A

one form to another

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8
Q

what is the process of energy being transformed from one form to another called ?

A

conservation of energy

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9
Q

what are the 10 different energy types ?

A 
magnetic
kinetic
heat 
light 
gravitational 
chemical 
sound 
elastic 
electrical 
nuclear
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10
Q

what are the energy transfers for a light bulb ?

A

electrical → light + heat

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11
Q

what are the energy transfers for a fan ?

A

electrical → kinetic + sound

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12
Q

what are the energy transfers for a kettle ?

A

electrical → heat + sound

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13
Q

what are the energy transfers for a iPad ?

A

chemical → light + sound → heat

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14
Q

what is the useful energy made in a light bulb ?

A

light

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15
Q

what is the useful energy made in a fan ?

A

kinetic

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16
Q

what is the useful energy made in a kettle ?

A

heat

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17
Q

what is the useful energy made in an iPad ?

A

light + sound

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18
Q

what is the wasted energy made in a light bulb ?

A

heat

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19
Q

what is the wasted energy made in a fan ?

A

sound

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20
Q

what is the wasted energy made in a kettle ?

A

sound

21
Q

what is the wasted energy made in an iPad ?

A

heat

22
Q

what is the equation for efficiency ?

A

efficiency = useful energy output ÷ total energy input

23
Q

how do you make the fraction given in the equation for efficiency a percentage ?

A

times it by 100

24
Q

what is the equation for work done ?

A

work done = force X distance moved (in direction of the force)

25
Q

what does work done = ?

A

work done = energy transferred

26
Q

how can energy be transferred by conduction ?

A
  • as material gets hotter, particles gain kinetic energy so vibrate more
  • hotter particles collide with colder ones and pass on their kinetic energy
  • when the kinetic energy of the colder particles increases the means their temperature has increased
27
Q

how can energy be transferred by convection in hot substances ?

A
  • heat up
  • space between particles has been increased due to thermal expansion
  • density has decreased
  • density is lower than the surrounding fluid so hotter fluid will rise
28
Q

how can energy be transferred by convection in cold substances ?

A
  • cool down
  • space between particles has decreased due to thermal expansion
  • density has increased
  • density is higher than the surrounding fluid so colder fluid will sink
29
Q

how can energy be transferred by infra red radiation ?

A
  • infra red radiation is absorbed by surfaces causing a rise in temperature
30
Q

which colour does infra red radiation work best in (best emitter and absorber) ?

A

matte black

31
Q

which state does convection work worst in ?

A

solids and a vacuum because a vacuum has no particles and the particles in a solid are unable to move

32
Q

which colour does infra red radiation work worst in (worst emitter and absorber) ?

A

silver

33
Q

how do convection currents work ?

A
  • radiator heats are, thermally expands, becomes less dense and rises
  • warm air rises there are less particles left behind cold air particles move in and take their place
  • warm air cools down, becomes less dense, sinks
34
Q

what is a conductor ?

A

a substance which passes on heat energy easily and quickly

35
Q

what is an insulator ?

A

a substance which takes a long time to pass on heat energy

36
Q

why does a saucepan have a metal bottom but a plastic handle ?

A
  • metal bottom is a good conductor so it takes up the heat energy quickly and passes it on quickly heating up the food
  • plastic handle is a bad conductor but a good insulator so it takes longer for the handle to pass on the heat energy and get hot meaning the person cooking can hold the handle without getting burnt
37
Q

do metals tend to be thermal conductors or insulators ?

A

thermal conductor

38
Q

does plastic tend to be a thermal conductor or insulator ?

A

thermal insulator

39
Q

how does double glazing work ?

A
  • gas or sometimes a vacuum is trapped between the panes of glass
  • gases are bad conductors so reduces heat loss by conduction
40
Q

how does a space blanket work ?

A
  • blanket is shiny silver so radiation that tries to escape is reflected back
41
Q

what is the equation for gravitational potential energy ?

A

gravitational potential energy = mass x gravitational force constant x height

42
Q

what is the symbol equation for gravitational potential energy ?

A

Ep = mgh

43
Q

what is the equation for kinetic energy ?

A

kinetic energy = 1/2 x mass x velocity ²

44
Q

what is the symbol equation for kinetic energy ?

A

Ek = 1/2mv ²

45
Q

what is the equation for power ?

A

power = work done or energy transferred ÷ time taken

46
Q

what is power when relating to the work done ?

A

rate at which work is done

47
Q

what is power when relating to the energy transferred ?

A

it is the rate at which energy is transferred

48
Q

what is conservation of energy ?

A

energy cannot be created or destroyed only transformed into different types

physics (8 decks)

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