y9 revision 2 Flashcards
list the 8 energy stores
thermal energy, chemical energy, nuclear energy, kinetic energy, elastic potential energy, magnetic energy, electrostatic energy, gravitational potential energy
name the four ways in which energy can be transferred
electrical, radiation, mechanical, heating
what is a closed system
where neither matter nor energy can enter or leave. the net charge in the total energy of closed system is always zero
what is the unit of energy?
joules (j)
what is gravitational potential energy equation, with units?
Ep= mgh
GPE = joules (j)
mass = kilograms (kg
height - metres (m)
what is the kinetic energy equation, with units?
Ek = 0.5 mv^2 KE = joules (j) mass = kilograms (kg) speed = metres per second (m/s)
what is the law of conservation of energy?
energy is not created or destroyed but transferred from one store to another
what is the equation of power? with units
P = E/t Power = watts (w) Energy = joules (j) Time = seconds (s)
where is heat lost in a house?
windows, roof, walls, doors and floors
what is the efficiency equation?
Efficiency = useful energy/ total energy Efficiency = useful power/ total power
define the term power
the rate of transfer of energy
describe the energy transfer when a moving car slows down
energy is transferred mechanically from the kinetic store of the car to the thermal store of the surrounding
some energy is dissipated to the thermal store of the surrounding
describe the energy transfer when electric kettle is used an elastic band
the electric current in a kettle transfers energy to the heating element’s thermal store of the surroundings
describe the energy transfer when battery powered toy car is used
energy is transferred electrically from chemical store of the battery to the kinetic store of the toy car - some of the energy is dissipated to the thermal store of the surrounding
describe the energy transfer when a falling apple hits the ground
energy is transferred from kinetic store of the apple and dissipated to the thermal store of surroundings by sound waves
name the unit that represents one joule transferred per second
watts (w)