3.2 - energy Flashcards
when is work done
when energy is transfered from 1 store to another
whats the equation linking work force and distance
work done= forcex distance
whats the unit for work
joules
energy is transfered when..
work is done
what is power
the rate at which energy is transfered or rate at which work is done
whatre the 2 equations for power
p=energy/time
or
p=work/time
whats the unit for power
watts
whats the formula for gravitational potential energy `(J)
massXgravityXheight
what is gravitational potential energy
the energy stored in a object due to its positition above earths surface due to gravity acting on an object
what happens when a system changes
energy is transfered
energy cannot be created nor…
destroyed
what is kinetic energy
the energy stored in moving objects
whats the formula for kinetic energy
1/2 x mass x v^2
what is elastic potential energy
energy stored in elastic objects when work is done on the object
how do u calculate the elastic potential energy in a stretched spring
1/2 x spring constant x extension ^2
what happens if a spring reaches its elastic potential
it wont be reverted to its normal shape
whatre the 3 things that can happen to energy
transferred usefully, stored or dissipated, but cannot be created or destroyed.
what happens when energy is transfered
only part of it may be usefully transferred; the rest is dissipated so that it is stored in less useful ways. This energy is often described as being ‘wasted’.
what 2 forces dissipate energy by heating their surroundings
friction and air resistance
whatre the 2 ways efficiency of a device can be calculated
efficiency = useful energy out /total energy in x100
and
efficiency = useful power out / total power in x 100
how can energy flow in systems be represented
Sankey diagrams.
whatre the factors that effect fossil fuel selection
ease of storage, energy content and safety.
what happens when fuels are used
some energy is transferred to the surroundings. Some fuels are more efficient than others.
whatre the impacts of using fuels
renewability and the environmental impacts of extraction, use and disposal.
