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Physics iGCSE > P2 - Work, energy and power > Flashcards

P2 - Work, energy and power Flashcards

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1
Q

List the energy stores (8)

A

Thermal, kinetic, gravitational potential, elastic, chemical, magnetic, electrostatic, nuclear

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2
Q

List the energy transfers (5)

A

Mechanical, electrical, heating, radiation (waves like sound and light)

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3
Q

Kinetic energy

A

The energy an object has because of its motion

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4
Q

Gravitational potential energy

A

Energy an object has due to its position above the surface of the Earth
- and object gains GPE when it is lifted and loses it when it falls

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5
Q

Elastic energy

A

Energy stored in an object that is stretched or compressed

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6
Q

Electrostatic energy

A

Potential energy that results from the interaction of charged particles - due to the force of attraction (or repulsion) between two charges

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7
Q

Magnetic energy

A

Energy from magnets and their surrounding magnetic fields - due to the force of attraction (or repulsion) between two magnets

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8
Q

Chemical energy

A

A form of potential energy that is stored in chemical bonds between atoms.
- found in fuels, foods or batteries

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9
Q

Nuclear energy

A

Energy stored in the nucleus of an atom

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10
Q

Thermal energy

A

Energy a substance has due to its temperature (sometimes known as internal energy)
- sum of the kinetic energy and chemical energy of the particles that make up an object

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11
Q

Fusion

A

Creation of energy by joining the nuclei of two atoms (joining)

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12
Q

Fission

A

The splitting of an atomic nucleus to release energy (splitting)

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13
Q

Mechanical energy transfer

A

Energy transferred via a force acting on a body/object
- e.g. collision

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14
Q

Electrical energy transfer

A

Electrical currents can transfer energy from a power source, delivering it to components within a circuit

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15
Q

Heating (energy transfer)

A

Thermal energy can be transferred by conduction, convection or radiation
- conduction: process by which heat energy is transmitted through collisions between neighbouring atoms or molecules
- convection: occurs when particles with a lot of heat energy in a liquid or gas move and take the place of particles with less heat energy

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16
Q

Radiation (energy transfer)

A

Energy transferred by light or sound waves

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17
Q

Law of Conservation of Energy

A

Energy cannot be created or destroyed, it can only be transferred from one store to another

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18
Q

Closed system

A

A system in which no energy transfers take place in or out of the energy stores of the system
- total amount of energy stays constant

19
Q

Open system

A

A system in which matter and energy can enter from or escape to the surroundings

20
Q

How is work done

A

Whenever any work is done, energy gets transferred (mechanically) from one store to another
- energy transfer (J) = work done (J)

21
Q

Work in directions (equal and opposite)

A
  • If a force acts in the direction that an object is moving, then the object will gain energy (usually in the form of kinetic energy)
  • If the force acts in the opposite direction to the movement then the object will lose energy (usually as heat)
22
Q

Gravitational field strength on Earth (and Moon)

A

The gravitational field strength (g) on the Earth is approximately 10 N/kg
- The gravitational field strength on the surface of the Moon is less than on the EarthThis means it would be easier to lift a mass on the Moon than on the Earth

23
Q

Efficiency

A

The ratio of the useful energy transferred by the device to the total energy supplied to the device

24
Q

What does high or low efficiency dicate about energy transfers

A

If a system has high efficiency, this means most of the energy transferred is useful
If a system has low efficiency, this means most of the energy transferred is wasted

25
Q

Power

A

The rate at which work is done

26
Q

Renewable energy

A

A resource that has a theoretically unlimited supply and is not depleted when used by humans.

27
Q

Non-renewable energy

A

A source of energy that has a finite supply capable of being used up completely

28
Q

List the main energy sources (8)

A

Solar energy
Wind
Bio-fuel
Hydroelectricity
Geothermal
Tidal
Nuclear
Fossil fuels

29
Q

Fossil fuels (desc., trans., ren. and adv./disadv.)

A

Burning fossil fuels produces steam which can turn turbines
- chemical energy → thermal energy → kinetic energy → electrical energy
Renewable: No
ADVANTAGES: reliable; can produce large amounts of energy on fairly short notice
DISADVANTAGES: produce significant green house gases and pollution

30
Q

Nuclear energy (desc., trans., ren. and adv./disadv.)

A

Nuclear fuel is reacted producing heat which creates steam
- nuclear energy → thermal energy → kinetic energy → electrical energy
Renewable: No
ADVANTAGES: reliable; produces no green house gases pr pollution; a large amount of energy is produced from a small amount of fuel
DISADVANTAGES: produces dangerous radioactive waste; take thousands of years to decay

31
Q

Bio-fuels (desc., trans., ren. and adv./disadv.)

A

Plant matter, ethanol or methane can be produced and used as a fuel in place of fossil fuels
- chemical energy → thermal energy → electrical energy
Renewable: Yes
ADVANTAGES: the carbon dioxide produced by burning the fuel is balanced by the carbon di. absorbed whilst producing is
DISADVANTAGES: Can take up a lot of land and consume resources that are needed for food production

32
Q

Wind (desc., trans., ren. and adv./disadv.)

A
33
Q

Hydroelectric energy (desc., trans., ren. and adv./disadv.)

A

Hydroelectric uses the GPE of water stored in reservoirs to turn turbines which generate electricity
- gravitational potential energy → kinetic energy → electrical energy
Renewable: Yes
ADVANTAGES: reliable and can produce large amount of energy at short notice; no pollution
DISADVANTAGES: can involve flooding a large area; destroying important wildlife habitats

34
Q

Tidal energy (desc., trans., ren. and adv./disadv.)

A

A dam is used to trap seawater at high tide, which can then be released through a turbine generating electricity
- kinetic energy → electrical energy
Renewable: Yes
ADVANTAGES: the tides are very predictable and large amounts of energy can be produced at small intervals
DISADVANTAGES: very few suitable locations; can cause environmental harm to estuaries and disrupt shipping

35
Q

Geothermal energy (desc., trans., ren. and adv./disadv.)

A

Heat from underground can be used to create steam, which spins turbine, producing electricity
- thermal energy → kinetic energy → electrical energy
Renewable: Yes
ADVANTAGES: reliable; geothermal stations are usually small
DISADVANTAGES: can result in the release of harmful gases from underground; not many places are suitable

36
Q

Solar energy (desc., trans., ren. and adv./disadv.)

A

Photovoltaic cells can use light to create electricity or thermal radiation from the sun can be used to warm water passing through black pipes
- nuclear energy → light & thermal energy → electrical energy
Renewable: Yes
ADVANTAGES: produces no green house gases or pollution; good for producing energy in remote places
DISADVANTAGES: not reliable (only works when its sunny); solar farms can use up lots of farmland

37
Q

Kinetic energy formula

A

KE=1/2mv^2 (joules)

38
Q

GPE formula

A

GPE = mgh (joules)

39
Q

Power formula

A

P = W/t (watts)

40
Q

Efficiency equation

A

Efficiency = useful energy output / total energy input (%)

41
Q

Gravity on earth

A

9.8 m/s^2

42
Q

Change in GPE equation

A

Change in GPE = mass x gravitational field strength x change in height

43
Q

Work done formula

A

W = Fs (joules)
(s = displacement)

44
Q

Efficience equation (2)

A

Efficiency = (useful power output / power input) x 100

Physics iGCSE (6 decks)

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