p1 - conservation and dissipation of energy

same as anki, js here for eoy cram

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how can energy be stored

stores

what are the different energy stores

• chemical
  - kinetic
  - gravitational
  - elastic potential energy
  - thermal

how can energy be transferred

• heating
  - waves
  - electric current
  - force

energy always what

conserves

what is a closed system

a system in which no energy transfers take place out of or into the energy stores of the system

when is work done

when a force makes an object to move

work done formula

work done = force x distance

when does the GPE of an object increase

when it mobes up

formula for change in gravitational potential energy

mass x gfs x change of height

the energy in kinetic energy depends on what

mass and speed

what is the kinetic energy store of an object

0.5 x mass x velocity^2

what is elastic potential energy

the energy stored in an elastic object when work is done on the object

elastic potential energy of a spring formula

o.5 x spring constant x extension^2

what is useful energy

energy in the place we want it and in the form we need it

what is wasted energy

energy that is not useful and is transferred by an undesired pathway

what happens to wasted energy

it is eventually spreads out to the surroundings in the form of thermal energy

the efficiency of a device formula

(useful energy transferred by the device / total energy supplied to the device) x 100

maximum efficiency

100%

why do machines waste energy

• friction between their moving parts
  - air resistance
  - electrical resistance
  - noise

how can machines be made more efficient + example

by reducing the energy they waste, eg lubrication

what does the perfect electrical device look like

designed for a particular purpose and should waste as little energy as possible

what is power

the rate of transfer of energy

what is the power of an appliance formula

P = E/t