P7.1 Flashcards
What is energy
Energy is a quantity that tells you what is possible, but doesn’t tell you what happens.
What is each energy store associated with
An equation
Equation for a thermal energy store
energy = mass x specific heat capacity x change in temperature
Equation for kinetic energy store
Energy = 1/2 x mass x velocity squared
Equation for gravitational potential energy
Energy = mass x gravitational field strength x height
Equation for nuclear energy
energy = change in mass x velocity of light squared
Equation for elastic energy
Energy = 1/2 x spring constant x extension squared
What are the 4 ways energy can be transferred
Mechanically, electrically, heating by particles, heating by radiation
Equation for a mechanical transfer
Work done = force x distance
Equation for an electrical transfer
Energy transferred = power x time
What is the law of conservation of energy
Energy can’t be created or destroyed. It can only be transferred between stores.
What happens in a closed system
In a closed system there is no net change in energy. No external forces act on the closed system and the system is not heated or cooled.
What are the 3 things needed for energy analysis
.Choose two points in a process
.Identify which stores have more or less energy in them at those points
.Work out which type of transfer has transferred energy between stores
What happens when breaking
The kinetic energy of the car is transferred to the thermal store of the break pads.
