bMechanicsbofbFluidsb
Chapterb2:bFluidbStaticsb
7b
©b2017bCengagebLearning®.bMaybnotbbebscanned,bcopiedborbduplicated,borbpostedbtobabpubli
clybaccessiblebwebsite,binbwholeborbinbpart.b
SolutionsbforbSectionsb2.1b–b2.4.2
1.bThebforcebshownbisbpartiallybduebtobabpressurebactingbuniformlyboverbthebareabofb100bcm2.
bThe
pressurebisbnearest:
(D)b346bkPa
Thebpressurebisbduebtobthebnormalbcomponentbofbthebforcebactingbonbthebarea.bWe
have
2
4
2
4000bNcos30
346b000bN/mbbbborbbb346bkPa
100b10bbm
F
p
A
−
°
=
=
=
×
2.bThebpressurebonbtheblowerbsurfacebofbthebcylinderbisb20bkPa.bIfbthebvariationbofbpressurebi
nbthe
verticalbdirectionbisbgivenbby
/
2400bPa/m,
pbz
∂b∂b=b−
bthebpressurebonbthebupperbsurfacebisbnearest:
(A)b19.52bkPa
Becausebthebvariationbisbconstant,bthebchangebinbpressurebcanbbebwrittenbas
upper
2400bPa/mb0b2bm
480bPa.bbbb
20
0b48
19b52bkPa
,.
.
.
p
p
z
p
z
Δb=b∂
Δb=b−
×
=b−
∴
=
−
=
∂
3.bAbwater-
wellbdrillerbmeasuresbthebwaterblevelbinbabwellbtobbeb20bftbbelowbthebsurface.bThebpoint
onbthebwellbisb250bftbbelowbthebsurface.bThebpressurebatbthebpointbisbestimatedbtobbe:
(C)b688bkPa
UsingbEq.b2.4.4,bthebpressurebis
3
2
9810bN/m
(250
20)bft
0.3048bm/ft
688b000bN/mbbbborbb688bkPa
p
=bγbh
=
×
−
×
=
Or,bwebcouldbusebEnglishbunitsbasbfollows:b
2
14b350b101b3
62b4b(250
20)
14b350blb/ft
Then,
, 685bkPa
14b7b144
,
.
.
,
.
.
p
γ bh
×
=
=
×
−
=
=
×
Thebdifferencebbetweenbthebtwobnumbersbisbduebtobthebaccuracybofbthebnumbersbused:b
14.7,b9810,b62.4,bandb101.3.b
DOWNLOADbTHEbTestbBankbforbMechanicsbofbFluidsbSIbEditionb5thbEdition
bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbPotter
nursytestbank.store
bMechanicsbofbFluids,b4thbEditionb
Chapterb2:bFluidbStaticsb
8b
©b2017bCengagebLearning®.bMaybnotbbebscanned,bcopiedborbduplicated,borbpostedbtobabpubli
clybaccessiblebwebsite,binbwholeborbinbpart.b
4.bTobcalculatebthebpressurebinbthebstandardbatmospherebatb6000bm,btheblapsebratebisbusedb(s
eebEq.
2.4.8).bThebpercentageberror,bconsideringbthebpressurebfrombTablebB.3binbthebAppendixbtobbe
morebaccurate,bisbnearest:
(B)b0.13b%
Equationb2.4.8byields
9b81b0b0065b287
0
atm
0
288b2
0b0065b6000
101b3
47b15bkPa
288b2
Chapterb2:bFluidbStaticsb
7b
©b2017bCengagebLearning®.bMaybnotbbebscanned,bcopiedborbduplicated,borbpostedbtobabpubli
clybaccessiblebwebsite,binbwholeborbinbpart.b
SolutionsbforbSectionsb2.1b–b2.4.2
1.bThebforcebshownbisbpartiallybduebtobabpressurebactingbuniformlyboverbthebareabofb100bcm2.
bThe
pressurebisbnearest:
(D)b346bkPa
Thebpressurebisbduebtobthebnormalbcomponentbofbthebforcebactingbonbthebarea.bWe
have
2
4
2
4000bNcos30
346b000bN/mbbbborbbb346bkPa
100b10bbm
F
p
A
−
°
=
=
=
×
2.bThebpressurebonbtheblowerbsurfacebofbthebcylinderbisb20bkPa.bIfbthebvariationbofbpressurebi
nbthe
verticalbdirectionbisbgivenbby
/
2400bPa/m,
pbz
∂b∂b=b−
bthebpressurebonbthebupperbsurfacebisbnearest:
(A)b19.52bkPa
Becausebthebvariationbisbconstant,bthebchangebinbpressurebcanbbebwrittenbas
upper
2400bPa/mb0b2bm
480bPa.bbbb
20
0b48
19b52bkPa
,.
.
.
p
p
z
p
z
Δb=b∂
Δb=b−
×
=b−
∴
=
−
=
∂
3.bAbwater-
wellbdrillerbmeasuresbthebwaterblevelbinbabwellbtobbeb20bftbbelowbthebsurface.bThebpoint
onbthebwellbisb250bftbbelowbthebsurface.bThebpressurebatbthebpointbisbestimatedbtobbe:
(C)b688bkPa
UsingbEq.b2.4.4,bthebpressurebis
3
2
9810bN/m
(250
20)bft
0.3048bm/ft
688b000bN/mbbbborbb688bkPa
p
=bγbh
=
×
−
×
=
Or,bwebcouldbusebEnglishbunitsbasbfollows:b
2
14b350b101b3
62b4b(250
20)
14b350blb/ft
Then,
, 685bkPa
14b7b144
,
.
.
,
.
.
p
γ bh
×
=
=
×
−
=
=
×
Thebdifferencebbetweenbthebtwobnumbersbisbduebtobthebaccuracybofbthebnumbersbused:b
14.7,b9810,b62.4,bandb101.3.b
DOWNLOADbTHEbTestbBankbforbMechanicsbofbFluidsbSIbEditionb5thbEdition
bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbPotter
nursytestbank.store
bMechanicsbofbFluids,b4thbEditionb
Chapterb2:bFluidbStaticsb
8b
©b2017bCengagebLearning®.bMaybnotbbebscanned,bcopiedborbduplicated,borbpostedbtobabpubli
clybaccessiblebwebsite,binbwholeborbinbpart.b
4.bTobcalculatebthebpressurebinbthebstandardbatmospherebatb6000bm,btheblapsebratebisbusedb(s
eebEq.
2.4.8).bThebpercentageberror,bconsideringbthebpressurebfrombTablebB.3binbthebAppendixbtobbe
morebaccurate,bisbnearest:
(B)b0.13b%
Equationb2.4.8byields
9b81b0b0065b287
0
atm
0
288b2
0b0065b6000
101b3
47b15bkPa
288b2
