conservation and dissipation of energy Flashcards

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1
Q

what is energy transferred between?

A

energy stores.

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2
Q

name the energy stores (8)

A
  1. thermal
  2. kinetic
  3. gravitational potential
  4. elastic potential
  5. chemical
  6. magnetic
  7. electrostatic
  8. nuclear
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3
Q

how is energy transferred?

A

mechanically (a force doing work)
electrically (moving charges)
heating
radiation (e.g. light or sound)

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4
Q

what is a system?

A

a name for an object or group of objects. (such as two colliding cars)

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5
Q

how can energy transfer within a system? (4 ways)

A

energy can transfer into the system.
energy can transfer out the system.
energy can transfer between objects.
energy can change stores.

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6
Q

what is a closed system?

A

a system where energy can not enter or leave.

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7
Q

how does energy change in a closed system?

A

it doesn’t 🤷

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8
Q

what is work done?

A

work done is another name for energy transferred.

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9
Q

how does work get done?

A

work is done when current flows or by force moving an object.

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10
Q

what is kinetic energy?

A

anything that moves has kinetic energy.

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11
Q

when is kinetic energy gained or lost?

A

kinetic energy is gained when an object speeds up.
kinetic energy is lost when an object slows down.

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12
Q

what is the formula for kinetic energy?

A

kinetic energy jules = 1/2 x mass kg x speed² m/s

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13
Q

what is gravitational potential energy?

A

the energy an object has due to it’s height above the earth’s surface.

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14
Q

why is energy transferred to the gravitation potential store?

A

lifting an object in a gravitational field requires energy or work which transfers energy to the gravitational store.

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15
Q

what is the formula for gravitation potential energy?

A

gpe jules = mass kg x gravitational field strength newtons/kg x height m

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16
Q

what happens when an object falls?

A

energy transfers from its gravitational energy store to its kinetic energy store.

17
Q

what is elastic potential energy?

A

energy stored when an object is stretched or squashed.

18
Q

what is the formula for elastic potential energy?

A

elastic potential energy jules = 1/2 x spring constant newtons/metre x extension² metres

19
Q

what is conservation of energy?

A

energy can be transferred but never created or destroyed.

20
Q

what is wasted energy in an energy transfer?

A

wasted energy is the amount of energy dissipated. (energy goes where you don’t want it)

21
Q

what is power?

A

power is the rate of energy transfer. (e.g. a powerful machine transfers a lot of energy in a short amount of time)

22
Q

what is the formula for power? (2)

A

power watts = energy transferred jules ÷ time seconds
power watts = work done jules ÷ time seconds

23
Q

how can you reduce energy dissipation?

A

lubrication or insulation.