Forces and energy Flashcards
define ‘work done’
the amount of energy transferred when a force causes something to be displaced
energy transferred= work done
if a man pushes a car and it doesn’t move there is no work done because nothing has been displaced, if a group of people move a car and it moves theres is work done because the car has been displaced
what happens to the work done to overcome friction?
work done to overcome frictionis transferred as energy that heats the objects that rub together and heats the surroundings
what happens to the work done to overcome friction?
work done to overcome friction is transferred as energy that heats the objects that rub together and heats the surroundings
what is the relationship between force and work done
they are directly proportional
define power in science
power is the rate at which energy is transferred or energy transferred per second
what happens to gpe of an object when it moves up and when it moves down?
when an object moves up the gpe increases when it moves down gpe decreases,
describe the conversion between gpe and kinetic energy when an object is thrown into the air
as the object moves up its gpe increases and kinetic energy decreases until it reaches its maximum point where there is no kinetic energy, the object comes down and the gpe decreases when the kinetic energy increases, when it reaches the floor there is no gpe or kinetic energy
what does the kinetic energy of an object depend on?
kinetic energy depends on mass and speed
what is meant by the ;conservation of energy’
no energy can be created or destroyed it can only be transferred.
energy can be stored in various ways for example gpe is stored in an object when lifted epe is stored in a rubber band when stretched
what is ‘useful energy’
energy that is transferred to where it is wanted; in a useful form
eg in a tv sound and light are useful energy
what is ‘wasted energy’
energy that is not usefully transferred
eg in a tv heat is wasted energy
what eventually happens to wasted energy
it dissipates (spreads out) to the surroundings energy becomes less useful the more it spreads out
what is meant by ‘efficiency’
efficiency is how well something transfers useful energy a device that transfers 50% useful energy is less effieint than a device that transfers 70% useful energy
