TakeQuiz
• Units• 32.174lbm*ft/s2 perlbf• 2.20462lbmperkg• 3.28084ftperm
• HWreview• Problem1• Reviewtheproblem,andyourapproach.
• Aloneorwithyourneighbor,organizetheproblem• Breakitup• Whataretheparts?• Whatisthemainidea?• Whatisthe“supportingcast”
HW—Problem1• Bigpicture
• Oneequation,1unknownf(v)• Putinf(v)=0form
• SubtractPfrombothsides• Usesolver:cellforV,cellforf(V)
• Supportingcast• Othervariables:P,R,T,a,b• Units:
• ConvertTtoK• Useconsistentunits:cm3,mol,bar,K• Choosegasconstant:Wikipedia
• CellsforP,R,T,a,b• CellforV• Cellforf(V)• GuessV=RT/P(idealgaslaw)• Solver:
• setcell[f(v)]toavalueof[0]• bychangingcell[V].
HW—Problem1• Bigpicture
• Oneequation,1unknownf(v)• Putinf(v)=0form
• SubtractPfrombothsides• Usesolver:cellforV,cellforf(V)
• Supportingcast• Othervariables:P,R,T,a,b• Units:
• ConvertTtoK• Useconsistentunits:cm3,mol,bar,K• Choosegasconstant:Wikipedia
• CellsforP,R,T,a,b• CellforV• Cellforf(V)• GuessV=RT/P(idealgaslaw)• Solver:
• setcell[f(v)]toavalueof[0]• bychangingcell[V].
Thisproblemisessentiallythesameastheproblemswedidinclass1equationin1unknown
Theequationisslightlyharderandhasafewotherknownparameters.
Problemthatarise:(1) Beverycarefulenteringtheformula;checkparentheses,signs(2) Beverycarefulwithunits;writethemalloutonpaperfirst
(3) Writeeachknownparameterwithunitsinadifferentcell(don’t“hardcode”thevalues)
HW—Problem3• Bigpicture
• Two2unknowns:x1,T• Putinf(v)=0form• Nosingleapproach
• Approach• Listallvariables:y1,y2,x1,x2,P,T,P1
s,P2s
• (TreatA,B,Casknownparameters)• 8variables
• Listallequations/values(weshouldget8)• Wecouldsolve8equationsin8
unknowns,butthatisoverkill• Massagetheequations
• 7and8areknownvalues• Solve3fory2.• Insert5and6into1and2• Replacex2 with1-x1 in1and2
• Nowwehave2equationsin2unknowns.
• BestWay• Writeoutall8equations,butonlyusethe
solverfor2equationsin2unknowns.Noalgegraneeded.
y1P = x1Ps1 (T )
y2P = x2P22 (T )
y1 + y2 = 1
x1 + x2 = 1
P s1 = P 2
1 (T ) = exp
A1 �
B1
T + C1
�
P s2 = P 2
2 (T ) = exp
A2 �
B2
T + C2
�
y1 = 0.33
P = 120kPa
1
2
3
4
5
6
78
HW—Problem3
y1P = x1Ps1 (T )
y2P = x2P22 (T )
y1 + y2 = 1
x1 + x2 = 1
P s1 = P 2
1 (T ) = exp
A1 �
B1
T + C1
�
P s2 = P 2
2 (T ) = exp
A2 �
B2
T + C2
�
y1 = 0.33
P = 120kPa
1
2
3
4
5
6
78
