Dynamics 1: Exam 1 Review

Thermodynamics

the study of equilibrium states and transformations among those states (often between heat and mechanical work)

Heat

energy transfer between system and surroundings

Temperature

measure of kinetic energy of molecules in a system

System

generic term for a sample of matter

Open System

freely exchange mass and energy

Ex: Open System

atmosphere (small scale)

Closed System

freely exchange energy, no exchange of mass

Ex: Closed System

atmosphere (large scale)

Isolated System

no energy or mass exchange 

Ex: Isolated System

the entire universe

State

the current instantaneous condition of a system

State Variables

temperature, pressure, and volume

Equilibrium

when a system’s properties are unchanging and its surroundings are also unchanging

Stable

system will return to equilibrium

Unstable

break system out of equilibrium

Conditionally Unstable

stable with respect to small changes, unstable with respect to others (metastable)

Transformation

a shift from an initial state to a final state

Reversible Transformation

successive infinitesimal states that maintain equilibrium

Is a reversible transformation possible?

not technically

Irreversible Transformation

once the transformation has occurred, the state cannot be reconstructed

Cyclic Transformation

returning to the original state—can be reversible or irreversible

Energy

the ability to do work

Potential Energy

stored energy due to position

Kinetic Energy 

energy of an object’s motion

Path Integrals

general integration along a curve

Line Integrals

integration of a vector field along a path

Exact Differential

path-independant

Inexact Differential

path-dependent (closed line integral)

Kinetic Theory of Heat

the average internal energy of a system is proportional to its temperature

Degrees of Freedom

the number of ways a molecule may move, rotate, or vibrate in space

Ideal Gas Assumptions

1) Random motion
2) No collision forces (this makes linear motion)
3) Collisions are perfectly elastic
4) Volume of individual molecules is negligible

Internal Energy

molecular collisions exert more pressure based on their internal energy

Ideal Gas Law is a combination of

Kinetic Theory of Heat + Pressure on a Surface equations

Gay-Lussac’s Law

found increasing temp +1°C increases volume by 1/273

Boyles’ Law

in isothermal transformation, pV = p’V’

Caveats of Ideal Gas Law

1) 3 variables → must hold one constant to have predictable result
2) humid air alters equation
3) gasses not ideal near absolute zero

Rd, Dry Air Gas Constant

Corrected R*/M to adjust to mass of dry air

Dalton’s Law of Partial Pressure

p_total = p₁ + p₂ + p_…

Work

how energy changes as a force acts over a distance

Work-Energy Theorem

work done on/by an object results in a change in the object’s kinetic energy

Work & Heat Differentials

both are inexact differentials

First Law of Thermodynamics

internal energy is external energy (heat) added minus work done by the system

Thermal Capacity

temperature change associated with a change in heat 

Enthalpy

internal energy + work (total heat content of a system)

Joule’s Law:

enthalpy is only a function of temp

Isothermal Transformation Example

hurricane, fog, Karnos cycle

Isochoric Transformation Example

rapid introduction of heat (nuclear bomb), small-scale soundwave

Isobaric Transformation Example

parcel at constant pressure changes volume as the background pressure changes

Cyclic Process Example

boundary layer

Adiabatic Process Example

a parcel rising si a small serios of adiabatic transformations

Important note of Isochoric Process

no work (δQ = 0)

Important note of Adiabatic Process

no heat (dQ = 0)

Poisson Relations

describe state variables for quasi-static adiabatic processes; Tp, TV, and pV

θ under adiabatic process

does not change

Uses for θ

1) traces atmospheric motion
2) heavily depends on temp & pressure
3) θ surfaces show rising motion, also parcels undergoing dry adiabatic transformations
4) constrains work done on/by parcel (because θ must stay constant)