Energy Stores and Systems-Notes
Energy Basics
Energy is transferred between different stores and objects, never used up.
Types of Energy Stores
Thermal energy stores
Kinetic energy stores
Gravitational potential energy stores
Elastic potential energy stores
Chemical energy stores
Magnetic energy stores
Electrostatic energy stores
Nuclear energy stores
Energy Transfer Methods
Mechanically (force doing work)
Electrically (work by moving charges)
By heating
By radiation (light, sound)
Understanding Systems
A system can be a single object or a group (e.g., air in a piston, colliding vehicles).
Energy can enter or leave a system or transfer between stores.
Closed systems have a net energy change of zero since matter and energy cannot enter or leave.
Energy Transfer by Heating
Example: Boiling water in a kettle. Heat is transferred to water's thermal energy store.
Energy Transfer by Doing Work
Work done is synonymous with energy transfer.
Example: Throwing a ball transfers energy from chemical to kinetic energy store.
Gravitational force accelerates a falling ball, transferring gravitational potential energy to kinetic energy.
In a car's brakes, kinetic energy is transferred to thermal energy through friction.
Collisions
In a collision, normal contact force transfers energy from the car's kinetic energy store to other stores like elastic potential, thermal, and sound energy.
Tip
Understand various energy stores and their transitions.