energy Flashcards

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1
Q

What is a system?

A

An object or group of objects.

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2
Q

When a ball hits a wall some kinetic energy is…

A

Transferred as sound.

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3
Q

What is energy measured in?

A

Joules.

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4
Q

What is the equation for kinetic energy?

A

1/2 x mass x speed squared.

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5
Q

What is elastic potential?

A

Energy stored in a spring when it is stretched.

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6
Q

What is the equation for elastic potential energy?

A

1/2 x spring constant x extension squared.

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7
Q

What is spring constant measured in?

A

Newtons per metre.

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8
Q

How do you calculate gravitational potential energy?

A

mass x gravitational field strength x height.

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9
Q

What is gravitational field strength measured in?

A

Newtons per kilogram.

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10
Q

What is power measured in?

A

Watts.

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11
Q

What 2 things is power the rate of?

A

Energy transferred and work done.

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12
Q

What are the 2 equations for power?

A

Energy transferred. Work done.
————————— or ——————-
Time. Time

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13
Q

Energy transfers cannot be…

A

Created or destroyed.

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14
Q

What 3 things can happen to energy transfers?

A

~They can be transferred usefully
~They can be stored
~They can be dissipated

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15
Q

What does lubrication do?

A

Reduces friction so less heat energy is lost.

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16
Q

What are 2 ways of reducing energy waste?

A

Lubrication and thermal insulation.

17
Q

If thermal conductivity is higher…

A

~Heat is allowed to travel through the material more easily
~So the rate of energy transfer by conduction across the material is higher

18
Q

What is efficiency the ratio of?

A

Useful work done by a machine to the energy supplied to it.

19
Q

What are the 2 equations for efficiency?

A

Useful energy output. Useful power output
—————————— or ———————————
Total energy input. Total power input

20
Q

Efficiency of a system can be increased by…

A

~Reducing waste output
~Recycling waste output

21
Q

What are the 6 renewable energy sources?

A

~Biofuel
~Wind
~Hydro-electricity
~Geothermal
~Tidal
~Solar

22
Q

Why are some energies renewable?

A

As they can be replenished as they are used.

23
Q

Why isn’t solar energy very reliable?

A

As it doesn’t work at night or in bad weather.

24
Q

What are 2 examples of non-renewable energies?

A

Fossil fuels and nuclear fuel.

25
Q

Why are non-renewable energy sources used for large scale energy supplies?

A

As they have a large output per kilogram.

26
Q

What are the 3 main energy uses?

A

Transport, electricity generation and heating.

27
Q

How does the extraction of energy have an impact on the environment?

A

~Fossil fuels involve destroying landscapes
~Wind turbines are seen as eye pollution

28
Q

What do fossil fuels release?

A

Harmful emissions.