topic 2 - conservation of energy Flashcards
kinetic energy store
the energy of a moving object
what does kinetic energy depend on
mass and speed
kinetic energy formula
KE = 1/2 x mass x speed^2
gravitational potential energy store
potential energy an object has due to the action of gravity on it
the energy gained by an object as it is lifted
what does GPE depend on
mass, height, gravitational field strength
gravitational potential energy formula
GPE = mass x gfs x change in vertical height
thermal energy store
energy of an object due to its temperature
elastic potential store
energy of a stretched spring or elastic band
chemical energy store
energy within a chemical substance
magnetic energy store
energy due to the force of attraction between two magnets
electrostatic energy store
energy due to force of attraction between two electrostatic charges
nuclear energy store
energy contained within an atom’s nucleus
energy released by two atomic nuclei in nuclear reactions
conservation of energy
energy can be stored, transferred and dissipated but never created or destroyed
what happens to energy in a closed system
in a closed system, total energy never changes
there is no NET change to the total energy
in what 4 ways can energy be transferred
mechanically
electrically
by heating
by radiation
how can energy be transferred mechanically
transferred by a force acting on an object
how can energy be transferred electrically
transferred by a charge doing the work
how can energy be transferred by heating
energy transferred from a hotter object to a cooler object
how can energy be transferred by radiation
energy is transferred by waves
energy transfers when an object is projected upwards/up a slope
work done against gravity
kinetic energy is transferred MECHANICALLY to gpe
energy transfers when a moving object hits an obstacle and example
eg. ball hitting bat
bat transfers kinetic energy mechanically to the ball
some energy is mechanically transferred to the thermal energy stores
rest of energy is transferred as sound
energy transfers when an object is being accelerated at a constant force and example
eg. rock dropping from a cliff
GPE is transferred mechanically to the kinetic energy store
energy transfers when a vehicle is slowing down
kinetic energy transferred mechanically and by heating to the thermal energy store of the road and the car
energy transfers when a kettle is boiling water
energy transferred electrically to the heating element
energy transferred by heating from the element to the thermal energy store of the water
what happens when work is done mechanically
there is often friction
the friction has to be overcome and the energy for this is transferred from kinetic energy to thermal energy
energy is often dissipated by heating (wasteful)
what tends to dissipate
heat, light and sound energy tend to dissipate
it is hard to gather the spreadout energy so the energy is less useful
what happens when energy is transferred from one store to another
when energy is transferred from one store to another, some energy is lost
efficiency
how much useful energy you get from a device compared to the energy that went into it
efficiency formula
efficiency = useful energy transferred (J)/ total energy supplied (J)
how can efficiency be improved in a mechanical system
to reduce unwanted energy produced in a mechanical system, you could reduce friction
- you could add bearings to prevent parts from rubbing directly together
- lubrication
how can efficiency be improved in a electrical system
to reduce unwanted energy produced in an electrical system, you could reduce resistance
- use lower resistance parts/components
- lower the electrical current
lubrication
lubrication can be used to reduce friction between two surfaces as they move
what does thermal insulation do
thermal insulation reduces the thermal energy lost by conduction
thermal conductivity
how well a material transfers energy via conduction
metals/solids have high thermal conductivity
gases have low thermal conductivity
to reduce rate of cooling, what should walls be like
walls should be thick and have low thermal conductivity
3 types of thermal insulation in buildings
loft insulation with fibreglass in
double glazed windows - two sheets of glass with air gap in-between
cavity walls - inner and outer walls with air in-between
energy resources
large banks of energy that can be transferred into a form that can be used by society
non-renewable energy resources (def + examples)
resources that will run out once day, natural resources that form underground over millions of years
eg.. coal, oil, natural gas
non-renewable energy resources features
typically burnt to provide energy
provide most of our energy
do damage to the environment
renewable energy resources (def + examples)
resources which will never run out as the energy used can be ‘renewed’
eg.. solar, wind, hydroelectricity, biofuel, tides
renewable energy resources features
don’t provide as much energy
reliant upon weather
still damage the environment, just to a lesser extent
what is non-renewable energy used for generally
non-renewable energy is used for more large-scale energy supplies due to the large energy output per kilogram of fuel
why have renewable resources become more important
because of the finite lifetime of fossil fuels
trends in energy resource use
during the Industrial revolution, fossil fuels were an important source of energy as it was easy to mine and provided lots of energy
since the start of the 21st century, electricity use has been slowly decreasing as appliances have become more efficient and we have been more careful with energy use in our homes
how is our energy produced
some of our energy is produced using fossil fuels (which we also burn to fuel cars and heat homes) and from nuclear power
what is the aim in terms of energy resources as we move forwards
the aim is to begin to use more renewable resources due to pressure on the government from the public and other countries
