conservation of energy principle - --energy cannot be created nor destroyed but it can be transformed
from one form to another if total energy remains constant.
first law of thermodynamics - --energy conservation principle
second law of thermodynamics - --energy is described by quantity and quality
processes occur in the direction of decreasing quality of energy
classical thermodynamics - --macroscopic approach to studying thermodynamics that does not require
knowledge of the behavior of the molecules
ex) examining air's properties (density, P, and T)
molecular/statistical thermodynamics - --microscopic approach to studying thermodynamics
focuses on the behavior of molecules
ex) examining the molecular makeup of air
conversion from foot to meter - --1 ft = 0.3048 m
conversion from lbm to kg - --1 lbm = 0.4536 kg
units of force - --1 N → force required to accelerate a mass of 1 kg at a rate of 1 m/s²
1 lbf = 4.448 N
units of work/energy - --1 J → the work done by a force of 1 N actioning of a distance of 1 m (1 N* 1
m)
1 calorie (English) = 4.1868 J
1 Btu = 1055 J
power (W) - --1 W → 1 J of work done in 1 s
how fast or slow energy is produced/work being done
as power ↑, work ↑ or time↓
1 hp = 746 W
system - --a system is defined as a quantity of matter or a region in space chosen for a study. it is
contained by a boundary
, surroundings - --the mass/region outside of the system/boundary
boundary - --the surface that separates the system from the surroundings
zero thickness, mass, and volume
can be moving (balloon), or flexible, or fixed
closed system with a fixed boundary - --there is no mass exchange, but energy change can still occur.
volume is fixed, energy is not necessarily fixed. the mass is controlled
closed system with a moving boundary - --there is no mass exchange, but energy change can still
occur. volume is changing, energy is not necessarily fixed. the mass is controlled
open system - --can have both mass and energy exchange. the volume is controlled.
property - --any characteristic of a system
ex) pressure, temperature, and density
extensive property - --dependent on the mass of the system
ex) mass, volume, and energy
can be converted into an intensive property by dividing by mass. these properties are known as
specific properties. changes when a system is divided into 2
intensive property - --independent of the mass of a system
ex) temperature, pressure, and density.
does not change when a system is divided into 2
continuum - --a continuum disregards the atomic nature of a substance and views it as a continuous,
homogeneous matter with no holes or gaps. matter is continuously distributed within the system. any
point can be assigned a property. (the molecular view has gaps between molecules so masses/values
can not be assigned to certain points where there are gaps)
continuum assumption - --valid if the characteristic dimension (length) of a system is much greater
than the mean free path of molecules. any length you can associate with a system is a characteristic
length.
mean free path - --the distance a molecule travels before collision with another molecule,
approximately 10^-8 m.
density - --density=mass/volume
ρ=m/V [kg/m³]
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