Conservation and Dissipation Flashcards
Kinetic Energy
The energy stored by objects that are moving
Gravitational potential energy
The potential energy stored in objects raised above the ground
Chemical energy
The energy stored in food, fuels and batteries
Thermal energy
The energy stored by hot objects
Elastic potential energy
The potential energy stored by stretched or squashed objects
What is a system
A system is an object or group of objects
Conservation of energy
In a closed system, energy cannot be created or destroyed. The total energy is constant.
What happens during all system changes?
In all system changes, energy is dissipated so that it is stored in less useful ways (wasted energy).
Dissipated energy ussually ends up as a thermal store in the surroundings.
How can you reduce unwanted energy transfers?
These unwanted energy transfers can be reduced using for example, lubrication (reduces friction) and insulation (to reduce the rate of thermal energy transfer)
Name the energy transfers when:
~A tennis ball is projected upwards
~A vehicle slowing down
~A battery powered drill is turned on
~A person sliding down a zip-wire
Tennis Ball Projected Upwards: Decreasing: Kinetic Increasing: Gravitational Potential
A vehicle slowing down Dec: Kinetic Inc: Thermal
A battery powered drill is turned on Dec: Chemical Inc: Kinetic, Thermal
A person sliding down a zip-wire Dec: Gravitational Potential Inc: Kinetic, Thermal
What is power?
Power is defined as the rate at which energy is transferred, or the rate at which work is done.
How can efficiency be calculated?
Efficiency= Useful Energy Output or Useful Power Output
——————————- ——————————-
Total energy input Total Power Input
What are all forms of energy and work done unit?
Joules
Work Done calculation
Work Done = Force x Distance
W= F x S
Force - Newtons, N
Distance Metres, M
Kinetic energy calculation
Kinetic Energy = ½ x mass x speed2
Ek = ½ x m x v2
Mass in kilograms, kg
Speed in metres per second, m/s
