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Physics IV > Conservation and dissipation of Energy - Topic 1 > Flashcards

Conservation and dissipation of Energy - Topic 1 Flashcards

1
Q

Name the 8 energy stores

A

kinetic, thermal, GPE, EPE, chemical, nuclear, magnetic, electrostatic
Eating Noodles Energises The Grannies Killing More Children

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2
Q

What is a system?

A

A single object or a group of objects

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3
Q

What is a closed system

A

They are systems where neither matter nor energy can enter or leave. The net change in the total energy of a closed system is always zero.

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4
Q

Magnetic energy is…

A

energy stored between the poles of magnetic objects

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5
Q

What are the 4 types of energy transfer?

A

-by radiation: waves carrying energy (e.g. light)
-** by heating**: conduction/ convection
- mechanically: (by forces), push or pull (physical movement )
- electrically: anything which uses electricity

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6
Q

Work done=?

A

force x distance

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7
Q

What is work done?

A

when energy is transferred from one store to another

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8
Q

Work done is measured in what?

A

Joules

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9
Q

Useful energy can be radiated as what?

A

Light

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10
Q

Sound is a form of which energy store?

A

kinetic

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11
Q

Kinetic energy =?

A

1/2 x mass x velocity squared (= 1/2 m v^2)

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12
Q

What is kinetic energy measured in?

A

Joules

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13
Q

GPE =?

A

mass(kg) x gravitational field strength(N/kg) x change in height(m)
= m g h

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14
Q

A value of what is most commonly used for the Earth’s gravitational field strength?

A

10

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15
Q

Change in height is always measured in what?

A

Metres

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16
Q

Energy lost from the g.p.e. store = ?

A

Energy gained in the kinetic energy store

17
Q

Elastic potential energy(J) = ?

A

1/2 x spring constant (N/m)x extension squared(m)
= 1/2 k e^2

18
Q

Energy is most commonly lost in what store due to what?

A

Thermal, friction

19
Q

What is the spring constant ?

A

A value which tells us how easily stretched a spring is
- different metals/thickness effects the spring constant

20
Q

In order to waste less energy, do what?

A
  • slow down
  • lubricate moving parts: to reduce friction and flow more easily between objects and coat them e.g. oils,
21
Q

What is dissipation?

A

When energy is lost to its surroundings

22
Q

Sound waves carry energy away. True or false?

A

True

23
Q

Efficiency is what?

A

how much of the original energy is used usefully

24
Q

Efficiency =?

A

= useful energy output/total energy input
OR
= useful power output / total power output

25
Q

What does an efficiency of 1 mean?

A

no energy is wasted in the system

26
Q

What is power?

A

The rate of energy transfer, or the rate of doing work

27
Q

Power (Watts) = ?

A

= Energy transferred (J) / time (s)
OR
= Work done (J) / time (s)

28
Q

How can you improve the efficiency of energy transfers?

A
  • insulating objects
  • lubricating moving objects
  • more streamlined
29
Q

How can you insulate your house from heat dissipation?

A
  • thick, low thermal conductivity walls : the thicker and lower the conductivity is the slower the rate of energy transfer
30
Q

what is the principle of conservation of energy

A

energy can be stored, transferred between stores and dissipated, CANNOT be created or destroyed

31
Q

what is the energy transfer stores of a ball rolling up a slope

A

energy transferred mechanically :
- **kinetic —> gravitational potential*
- some energy is transferred mechanically to the thermal energy stores of the ball and the slope due to friction

32
Q

describe the energy store transfers of a moving object hitting an obstacle

A
  • obstacle kinetic energy –> moving objects kinetic energy
    -some kinetic energy of obstacle is transferred to thermal energy store of object and obstacle
  • rest energy is wasted to sound
33
Q

describe the energy store transfers of an electric kettle boiling water

A

Energy transfers electrically from the electrical store of the mains power supply to the thermal store of the water.
- some energy wasted to thermal energy store of the surroundings

34
Q

describe the energy transfer of an object accelerated by a constant force

A
  • Work is done by a force on an object.
  • work done –> kinetic store.
35
Q

describe the energy transfer of a vehicle slowing down

A
  • when moving energy is inkinetic store
    when decelerates, energy transferred from kinetic –> thermal sore of the surroundings (dissipated)
  • energy transferred by heating due to friction
36
Q

energy transfer by heating can happen in 3 different ways:

A
  • radiation
  • conduction
  • convection

Physics IV (17 decks)

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