Physics: energy

What is the equation linking kinetic energy, mass and velocity?

Ek= 0.5mv2 or ½mv2 or mv2/2

What are the units of energy?

joules (J)

What are the units of mass?

kilograms (kg)

What are the units of velocity?

metres per second (m/s)

What equation links gravitational field strength, gravitational potential energy and height?

Ep=mgh

What are the units of gravitational field strength?

newtons per kilogram (N/kg)

What equation links energy transferred, power and time?

P=E/t

What are the units of power?

watts (W)

What is the definition of power?

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

What is the equation linking power, time and work done?

P=W/t

What are the units of work done?

joules (J)

What is the equation for calculating energy efficiency?

Efficiency = useful energy output/total energy input

What is the equation for calculating power efficiency?

Efficiency = useful power output/total power input

What type of energy transfer takes place when a force moves an object through a certain distance?

Mechanical transfer

Mechanical (energy) transfer takes place when...?

...a force moves an object through a distance

Electrical (energy) transfer takes place when...?

...a charge moves (or a current flows in a circuit)?

What energy transfer takes place when a charge moves?

Electrical (transfer)

What is the energy transferred by electromagnetic radiation?

Radiation (transfer)

Radiation transfer is energy transferred by...?

... electromagnetic radiation.

Heat (thermal) energy transfer takes place when...?

... an object gains or loses heat

When an object is heated the energy transfer is ...?

heat transfer

List the 4 ways in which energy is transferred.

Mechanical, electrical, radiation and heat (thermal).

List 4 energy stores.

Four from: chemical, kinetic, gravitational potential, elastic potential, internal (includes thermal), nuclear, magnetic, electrostatic.

Energy stored in any moving object.

Kinetic energy

What is a kinetic energy store

Energy stored in objects which move

Chemical energy is stored as...?

chemicals waiting to react

A battery is a store of __________ energy.

chemical

Food is a store of __________ energy.

chemical

A moving object is a store of ____________ energy

kinetic

What is a gravitational potential store?

Energy stored in objects raised up against the force of gravity.

A rock at the top of a hill is a store of ___________ energy.

gravitational potential

What is an elastic potential store?

Energy stored in an object which has been stretched or compressed.

A compressed spring is a store of ___________ energy

elastic potential

An inflated balloon is a store of __________ energy

elastic potential

The internal energy store is...

the total kinetic energy and potential energy of all the particles that make up a system

The internal energy store of an object can be changed by...?

heating or cooling

Energy stored in the nuclei of atoms is in the __________ store.

nuclear

What is a nuclear energy store?

Energy stored in the nuclei of atoms that can be released by fusion or fission (splitting).

What is the name of the process in which the nuclei of atoms fuse together?

Nuclear fusion

What is the name of the process in which the nucleus of an atom splits?

Nuclear fission

What is the magnetic energy store?

Energy stored when two magnets (or electromagnets) are attracting or repelling; or when a magnet and a magnetic material are attracting.

What is the electrostatic energy store?

Energy stored when electric charges are attracting or repelling

What is renewable energy?

Energy from natural sources that is continually replenished, so does not run out (renewable sources)

What is non-renewable energy?

Energy from natural sources that is being used up faster than it can be replenished (non-renewable sources)

Name two non-renewable energy resources

Fossil fuels, nuclear fuel

What are some advantages of fossil fuels as an energy resource?

Reliable, cheap

What is a reliable energy source

One which can generate energy all the time.

What are some disadvantages of burning fossil fuels?

Carbon dioxide (greenhouse gas) is produced which contributes to global warming. Can produce sulphur dioxide which causes acid rain.

What are some advantages of nuclear fuel?

No carbon dioxide produced, reliable.

What are some disadvantages of nuclear fuel?

Nuclear waste remains radioactive for thousands of years. Expensive to build and decommission

List 4 renewable energy resources.

Any 4 from: biofuel, wind, hydroelectricity, geothermal, tidal, wave, solar.

What are some advantages of biofuels?

Carbon neutral, reliable

What are some disadvantages of biofuels?

Production of fuel can damage ecosystems and reduce variety and amount of food crops grown

What are some advantages of wind power?

No carbon dioxide produced, renewable

What are some disadvantages of wind power?

Unreliable, expensive to buy and erect, noise pollution

If wind speed doubles, by what factor does the energy output of a wind turbine increase? (ext)

8 - doubling speed increases KE by 22, but the mass of wind per second also doubles, so 2x2x2 in total

What are some advantages of hydroelectricity?

No carbon dioxide produced, renewable, pumped storage

What are some disadvantages of hydroelectricty?

Blocks rivers preventing fish migration, may be unreliable (e.g. during droughts)

What is a pumped storage scheme?

A hydroelectric energy storage scheme which uses surplus or cheap electricity to pump water up to a reservoir

What are some advantages of pumped storage schemes?

They use cheap or surplus electrical energy and can store energy for use during periods of high demand

What are some advantages of geothermal energy?

Doesn't damage ecosystems, reliable.

What are some disadvantages of geothermal energy?

The process can release greenhouse gases such as CO2 and methane.These contribute to global warming.

What are some advantages of tidal energy?

No carbon dioxide produced; reliable; renewable

What are some disadvantages of tidal energy?

Construction may damage tidal ecosystem

What are some advantages of wave power?

No carbon dioxide produced; renewable

What are some disadvantages of wave power?

Unreliable - may not produce enough electricity during calm seas

What are some advantages of solar power?

No carbon dioxide produced; renewable

What are some disadvantages of solar power?

Unreliable - no electricity produced at night and limited on cloudy days; solar cells inefficient and expensive

What term is used to describe energy becoming spread out or transferred to a "wasted" store?

Dissipation

What energy store does most energy end up in at the end of any transfer process?

Thermal store of the surroundings (wasted energy)

What term is used to describe a method for reducing unwanted energy transfers by reducing friction between moving parts?

Lubrication

What is a thermal insulator?

A material with low thermal conductivity which reduces thermal energy transfers.

What is the name for a method of reducing energy transfers by the use of low-conductivity materials ?

insulation

What is the law of conservation of energy?

Energy cannot be created or destroyed but only transferred from one store to another.

Define specific heat capacity

The energy needed to raise the temperature of 1 kg of a material by 1ᵒC

State the unit of specific heat capacity.

joules per kilogram degree Celsius (J/kg°C)