P7.1 Flashcards
state the law of energy conservation
energy cannot be created or destroyed ( it can only be transferred into different forms)
describe the energy changes that occur in a filament light-bulb
electrical energy is transferred into light and heat energy
light is a useful energy form, heat is waste energy
what type of energy is stored when an object is lifted up?
gravitational potential energy
what type of energy does a moving object have
kinetic energy
what type of energy does a stretched spring store
elastic potential energy
state any changes in the total energy of a ball that is kicked, assuming that no external forces act
the total energy of the system remains constant due to the conservation of energy
what is the equation for kinetic energy
E(J) = 1/2m(kg) x v(m/s)^2
describe the energy changes involved when a ball is thrown upwards and then returns to its starting position. Ignore air resistance
upwards: KE is converted to GPE
peak : maximum GPE, zero KE
downwards: GPE is converted to KE
describe the energy transfers for a bungee jumper
when falling, the GPE is converted to KE of jumper
As the cord tightens, KE is converted and stores as EPE
at lowest point, the jumpers initial GPE equals the EPE stored in the cord.
explain why a bungee jumper slows down once the cord begins to stretch
kinetic energy decreases since it is converted to elastic potential energy
since KE is proportion to (velocity)^2 as KE decreases, so does velocity
what is the equation for elastic potential energy
E(J) = 1/2 k(N/m) x(Extension, m)^2
what is the equation for gravitational potential energy
E(J) = m(kg) x g(N/kg) x h(m)
what unit of power is normally used for domestic electricity
Kilowatt (kW)
what is the unit of energy associated with the kW?
the kilowatt hour, kWh
