Class Three Flashcards
closed system
environment cannot contribute matter to it
isolated system
environment cannot contribute energy or matter
open system
environment is free to interact with the system
how can the total energy in a system change
if energy is transferred into or out of a system
temperature vs thermal energy
temperature = intensive
thermal energy = extensive
what is heat (q)
transfer of thermal energy between a system and its environment
what does the zeroth law of thermodynamics state
objects A and B = thermal equilibrium
objects B and C = thermal equilibrium
then A and C must be in equilibrium as well
kinetic energy and temperature equation
what is kb and when is it used
1.38 x 10-23 J/K
used when looking at the relationship with kinetic energy and temperature
three ways heat transfer occurs
conduction
convection
radiation
what conducts heat well
metals
what is convection
heat expanding + becoming less dense than surrounding air → heat rise
what is radiation
heat transfer by absorption of energy carried by light waves
as the temperature of materials increase..
they expand
first law of thermodynamics
total energy of the universe is constant → energy cannot be created or destroyed
equation for first law of thermodynamics
difference in E = Q - W
when is work (W) considered positive
when work is being done by the system on the environment
what is an isobaric process
one that occurs at constant pressure
what is an isochoric process
one that maintains a constant volume
is work done in isochoric processes
no
when does an isothermal process occur
when heat is allowed to pass freely between a system and its environment
in an isobaric process..
W = P (change in V)
in an isochoric process..
W = 0
change in E = Q
in an isothermal process..
change in E = 0
Q = W
what happens in an adiabatic process
no heat is transferred between the system and the environment (all energy is transferred as work)
second law of thermodynamics
entry of an isolated system either stays the same or increases during thermodynamic processes
first law equation for isobaric processes
delta E = Q - (P)(delta V)
which process has delta E = 0
isochoric processes
first law equation for isothermal processes
Q = W
first law for adiabatic processes
delta E = - W
isothermal vs adiabatic
isothermal = temp is constant but heat moves in/out
adiabatic = no heat moves in/out but temp changes
what is density
mass / volume
density of water
1 g / cm3
what is specific gravity
how dense something is compared to water
density of substance / density of water
for which phase does the density change with pressure/temperature
gas, not liquids or gases
density of an ideal gas
mP / nRT
Fgrav formula for fluids questions
Fgrav = pVg
density x volume x gravity
pressure for fluids formula
P = force / area
hydrostatic gauge pressure formula
Pgauge = pfluidgD
g = gravity
D = depth of sheet
incompressible liquids
density is constant (doesn’t increase with depth)
what is buoyancy
net upward fluid force
Archimedes’ Principle
the magnitude of the buoyant force is equal to the weight of the fluid displaced by the object
Archimedes’ Principle formula
FBuoy = pfluidVsubg
floating object in equilibrium on surface equation
wobject = FBuoy
Vsub / V = pobject / pfluid
what does it mean if pobject > pfluid
then the object will float
and fraction of its volume thats submerged = ratio of its density to fluid’s density
Pascal’s law
pressure applied to an enclosed fluid will be transmitted without a change in magnitude to every point of the fluid and to the walls of the container
slow rate equation
f = Av
surface tension ____ as temperature increases
decreases
continuity equation (flow rate)
A1v1 = A2v2
if a tube narrows.. the flow speed ___
increases
4 requirements for an ideal fluid
fluid is incompressible
there is negligible viscosity
flow is laminar
flow rate is steady
the Bernoulli effect
pressure is lower where flow speed is greater
3 ways forces can be applied to an object
tension (stretching)
compression (squeezing)
shear (bending)
stress formula
force / area
tensile/compressive strain formula
change in length / original length
shear strain formula
distance of shear / original length
Hooke’s law
stress and strain are proportional
Young’s modulus
constant of proportionality for tensile/compressive stress
shear modulus
constant of proportionality for shear stress
the stronger the intermolecular bonds, the ____ the modulus
greater
tension/compression formila
delta L = F (original length) / EA
shear formula
X = F (original length) / AG
faster flow speed = ____ pressure
lower
resistivity is ____ proportional to temperature
linearly
