9. Work and Energy Flashcards
Define energy
the capacity for doing work
1st law of thermodynamics
- energy can neither be created nor destroyed
* the law of conservation of energy
Forms of energy
- Chemical
- potential
- nuclear
- kinetic
- thermal
- electrical
Define work
Refer to energy transfer that occurs when an object is moved over a distance by an external force
•the energy that flows or that is transferred into or out of a system
Define systems and environment
- term used for the objects or objects of interest
* environment is everything else that may interact with the system
3 types of systems
Isolated, closed, open
Isolated systems
do not interact with the environment
•e.g. thermos - not exchanging energy or matter with env
Close systems
Exchange energy with the environment but not matter
•e.g. coffee in cup with lid - closed but still gets cold
open systems
Exchange both energy and matter with their environment
•coffee in a mug - heat loss and evaporation
Signs of work
- positive when work is done ON the system
* negative when work is done BY the system
SI unit of work
Joule
Kinetic energy
Energy an object has as a result of its motion
Elastic collision kinetic energy
A collision in which there is no net loss in kinetic energy in the system as a result of the collision
Potential energy
The amount of stored energy an object has as the results of its position
Latent heat
Energy stored in the phase of matter
• dissipated from skin during perspiration because it leads to water evaporating from the skin surface
