Topic 1.7 - Energy, Work and Power Flashcards Preview

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Flashcards in Topic 1.7 - Energy, Work and Power Deck (20)
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1

What type of energy is stored in a moving object?

Kinetic energy.

2

What happens, in terms of energy, when an object is lifted?

Its gravitational potential energy increases.

3

Give an equation for kinetic energy

kinetic energy (J) = ½ x mass (kg) x velocity² (m/s)

E = ½mv²

4

Give an equation for gravitational potential energy

Gravitational potential energy (J) = mass (kg) x height (m) x gravitational field strength (N/kg)

E = mgh

5

When work is done against friction or resistance, what happens?

There is less of a change in kinetic energy because some energy is dissipated through heating.

6

What is the original source of most of the energy on Earth?

The sun

7

What forms of energy do not ultimately come from the sun?

  • Geothermal
  • Nuclear
  • Tidal

8

What is the source of the sun’s energy?

Nuclear fusion.

9

What are the main energy resources available to humans?

  • Fossil fuels (oil, gas and coal)
  • nuclear fuels
  • biofuels
  • wind
  • hydroelectricity
  • tides and solar energy

10

Define renewable energy.

Energy from a source which does not run out, so can be replenished.

11

Which energy sources are non-renewable?

  • Fossil fuels
  • Nuclear fuel

12

Which energy sources are renewable?

  • Biofuels
  • Wind
  • Hydroelectric and tidal energy
  • Geothermal energy
  • Solar power

13

Why is non-renewable energy used to provide electricity on a large scale?

Non-renewable sources tend to have a larger energy output per kilogram of fuel.

14

What is efficiency?

The ratio of useful work done to energy supplied, often given as a percentage, i.e. the percentage of energy which is converted to a useful form.

15

Give the equation for efficiency

Efficiency = Useful energy output/Total energy input 

convert into percentage by multiplying the number by 100.

16

How can the efficiency of a system be increased?

  • Reducing waste output (by lubrication, thermal insulation etc.)
  • Recycling waste output (eg. recycling thermal waste energy as input energy)

17

Define work done.

  • Work is done on an object when energy is transferred (from one form to another)
  • Equal to the product of force and distance

18

Give the equation for work done

  • work done (J) = force (N) x distance (m)
  • W = Fd

19

Define power.

Power is the rate at which energy is transferred, or the rate at which work is done.

20

Give an equation for power

  • power (W) = energy (J) ÷ time (s)
  • power (W) = work done (J) ÷ time (s)