Energy: the quantity transferred whenever a change happens in joules

Energy stores: potential energy

• Kinetic energy

• Gravitational potential energy (GPE)

• Chemical energy

• elastic energy

• nuclear energy

• electrostatic energy

• internal (thermal energy)

Energy transfers:

• Forces (mechanical work)

• electrical currents

• Heating

• Waves

Energy can be transferred from one store to another even in one object

Conservation of energy: in any energy transfer, the total amount of energy before and after is constant

energy efficiency: energy that is used/wasted

GPE: an object’s height above ground

• Higher = greater GPE

• Heavier → greater force is needed to lift it → greater GPE

• change in GPE = weight x change in height

Kinetic energy: energy in an object when it is moving

• Greater mass = greater kinetic energy

• greater speed = greater kinetic energy

• kinetic energy = ½ x mass x velocity

  • Ek = 1/2mv²

Solar:

• Renewable → does not contribute to global warming

• No fuel cost

• Expensive initial building cost

• Unreliable → intensity of sunlight varies

Wind:

• Renewable

• No fuel cost

• Unreliable → speed of wind varies

• can be noisy and spoil appearances of places

• expensive

Waves:

• Renewable

• No fuel cost

• Expensive

• Unreliable→ height of waves can vary

Hydroelectric:

• Renewable

• Safe, clean, reliable

• expensive building costs

• dams and reservoirs floods lands

Biofuels:

• Renewable

• Reliable → burnt when needed

• burning fuels indoors can affect health

• land can be used to grow biofuels for profit rather than food

Fossil fuels:

• produce a large amount of energy

• reliable → burn more when electricity is needed

• Non-renewable

• Produces sulfer dioxide → acid rain

• Releases carbon dioxide → greenhouse effect and global warming

Nuclear:

• Provides lost of energy from a small mass

• Very concentrated store of energy in the form of nuclear energy

• Non-renewable

• waste is radioactive

• accidents can be catastrophic

Geothermal:

• Renewable

• No fuel cost

• Scarce availability

Tidal:

• Renewable

• Tides are predictable → reliable

• Expensive initial building costs

• Can destroy important habitat

Nuclear fusion vs fission

Nuclear fusion: nuclei join together → energy is released

• requires high pressures and temperature

Nuclear fission: large nucleus splits into smaller nuclei → releases energy

Work done = energy transferred

greater force = more work

distance moved in the direction of the force → moves more = more work done

work done = force x distance

• w = Fd

• unit: mgh

The rate at which a force does work (transfers energy)

Increase power by:

• lifting a heavier object in the same time

• lifting an object quicker

power = work done/time

• p = w/t

power = energy transferred/time

units: watts

• 1 W = 1 J/s