fluida

1. Pesawat dapat terbang karena mengalami gaya angkat yang bebas pada sayapnya.
A. Fluida Statis
B. Viskositas Fluida
C. Fluida Dinamis
139
Fluida
Bab
6
Hasil yang harus Anda capai:
menerapkan konsep dan prinsip mekanika klasik sistem kontinu dalam
menyelesaikan masalah.
Setelah mempelajari bab ini, Anda harus mampu:
+:FC6=@6=C967:FH6CL6B:C6E6E:G6K6H96E6HH:F76C+:G6K6H
96E6H H:F76C @6F:C6 B:C6A6B 6L6 6C@6H L6C 7:G6F
6L6 6C@6H
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696CL6 E:F7:966C @:8:E6H6C 6AF 96F ;AI96 I96F6 9 6H6G G6L6E 9:C6C
9 76K6= G6L6E
+FCGE H:FG:7IH B:FIE6@6C 6EA@6G 96F E:FG6B66C
:FCDIAA
6A6B 767 C C96 6@6C 7:A6?6F H:CH6C ;AI96 GH6HG 96C ;AI96
9C6BG
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G:=6F =6F
Sumber: www.chez.com
menganalisis hukum-hukum yang berhubungan dengan fluida statis dan
dinamis serta penerapannya dalam kehidupan sehari-hari.

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A. Fluida Statis
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1. Tekanan
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Gambar 6.1
Tekanan yang
dilakukan seorang anak
terhadap meja.
w
A
h
140 Mudah dan Aktif Belajar Fisika untuk Kelas XI
%
P
:H:F6C6C
% H:@6C6C )B E6G86A
6L6 )
AI6G 796C H:@6C B
2. Tekanan Hidrostatik
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7:FG M6H 86F 7:FB6GG6 ?:CG
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Gambar 6.2
Tekanan hidrostatik
pada dasar tabung.
AD6BBIA6:B6G=6CL69:C6CB:C8:AIE@6CCL6@:
96A6B6F
(:C6E6CL6BI@96E6H7:F?6A6C96H6GE:FBI@66C
6F
%:A6G@6C9:C6C76=6G6BC96G:C9F86F6@:F?696F
J:CHIFB:H:F96CEE6EHDH
Tes Kompetensi Awal

3. A B C
D
B
h2
Fluida 141
@:96A6B6C M6H 86F B
E:F8:E6H6C F6JH6G BG
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#
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C
A
h1
air
Gambar 6.4
Pipa U diisi dua zat cair berbeda,
tekanan di A sama dengan
tekanan di B.
Aktivitas Fisika 6.1
Tekanan Hidrostatik
Tujuan Percobaan
Memahami tekanan hidrostatika
Alat-Alat Percobaan
1. Sebuah ember
2. dua buah gelas plastik bening
Langkah-Langkah Percobaan
1. Isilah ember dengan air.
2. Jawablah pertanyaan berikut sebelum melakukan percobaan.
a. Apa yang akan terjadi jika sebuah gelas plastik dicelupkan perlahan ke
dalam air dalam keadaan terbalik? Jelaskan apa yang akan terjadi, berikut
alasannya.
b. Lakukan hal yang sama, namun dengan gelas yang diberi lubang pada
dasar gelasnya. Jelaskan apa yang akan terjadi, berikut alasannya.
3. Buktikanlah jawaban Anda dengan melakukan percobaan.
4. Buatlah hukum tentang tekanan menurut versi Anda, berdasarkan jawaban
dan hasil percobaan yang Anda peroleh.
5. Bandingkanlah dengan hukum hidrostatika yang telah Anda pelajari.
6. Buatlah kesimpulan dari percobaan tersebut.
Contoh 6.1
.:7I6=H:BE6H6F7:F7:CHI@@I7IGB:BA@E6C?6CFIGI@

5. 8B9G

6. AH:F6F
B6GG6?:CG6F

7. @B
%@6

8. BGH:CHI@6CA6=
6
H:@6C6C=9FDGH6H@E69696G6F@I7IG
7
6L6=9FDGH6H@E69696G6F@I7IG96C
8
6L6=9FDGH6H@E696HH@L6C7:F?6F6@

9. B96FE:FBI@66C6F
Gambar 6.3
Tekanan hidrostatik pada titik A,
B, dan C adalah sama.
h

10. +6966B76F7:F@IHG:7I6=EE67:F7:CHI@=IFI;09G9:C6C6F
8B
6F 6@EE6G:7:A6=@F9G7:CGC9:C6C

11. 8BG:HC8B
.:7:A6=
7:CGC @6C6C 9G BCL6@ H6C6= 9:C6C

12. 8B G:HC 8B
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BCL6@ E:F7:966CHC6F6CH6F6EE6@6C6C96CEE6@F
1
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13. 8B
7:CGC

14. 8B
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8B
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7:CGC BCL6@
Q

15. Q

16. Q
8B
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8B
3. Hukum Pascal
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piston
zat cair
Gambar 6.5
Tabung Pascal
F2
A2
p2
p1 F1
A1
P
142 Mudah dan Aktif Belajar Fisika untuk Kelas XI
h3
h2
B
h { 1
bensin
minyak
tanah
air
A
Contoh 6.2
hB
hA
s = 60 cm
1
@:H6=I

17. AH:F

18. B

19. @B

20. BG

21. B
'

22. 8B

23. B

24. B

25. B

26. B
6
%

29. @BQ

30. BGQ

31. B

34. +6
7
%

37. +6Q

38. B

40. )
8
%

43. @BQ

44. BGQ

45. B

47. +6
%

49. +6Q

50. B

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57. )96C6L6=9FDGH6HGE696HH@696A6=

59. )
Gambar 6.6
Prinsip kerja dongkrak hidrolik.

60. F2
F1
Sumber: Republika, 19 November 2005
Fluida 143
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74. )
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75. Q

78. Q

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Tokoh
Douglas Dean Osheroff
(1945 – sekarang)
Douglas Dean Osheroff dilahirkan
pada tahun 1945. Setelah
menyelesaikan pendidikan
sarjananya di California Institute Of
Technology, ia pindah ke Cornell
University untuk mengambil gelar
doktor. Di sana, ia bertemu dengan
David M. Lee dan Robert C.
Richardson. Bersama dua koleganya
tersebut, ia melakukan penelitian
selama bertahun-tahun sampai
menemukan satu fenomena yang
menghebohkan dunia ilmiah, yaitu
superfluiditas. Superfluiditas
tersebut terjadi ketika helium-3
didinginkan mendekati suhu nol
mutlak (–273,15°C). Pada suhu
tersebut, helium-3 tidak lagi
memiliki viskositas dan friksi
sehingga dapat meluap dari sebuah
cangkir datar melalui pori-pori yang
teramat kecil. Fenomena lainnya
adalah helium-3 ini dapat melawan
gaya gravitasi Bumi. Atas penemuan-nya
ini, Osherhof bersama kedua
rekannya mendapat hadiah Nobel
pada tahun 1996.
Contoh 6.3
Gambar 6.7
Pengangkat hidrolik
menerapkan Konsep Hukum
Pascal.

85. Gambar 6.8
Berkurangnya berat benda
di dalam zat cair disebabkan
oleh gaya ke atas yang
dikerjakan oleh zat cair.
Gambar 6.9
Perahu dapat terapung di atas air
karena massa jenisnya lebih kecil
dari massa jenis air.
4. Hukum Archimedes
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(G6A@6C 76AD@ H:FG:7IH B:BA@ 7:F6H

86. ) @:BI96C 76AD@ 9B6GI@@6C
@:96A6B7:?6C6L6C7:FG6F)-
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BG6ACL6 B:C?69 )
(:CIFIH C96 6E6@6= L6C B:CL:767@6C
7:F@IF6CCL6 7:F6H 76AD@ H:FG:7IH :F@IF6CCL6 7:F6H 76AD@ @:H@6
9B6GI@@6C @: 96A6B 6F 9G:767@6C DA:= 696CL6 6L6 H:@6C @: 6H6G 96F
6F
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.( -# %# # $! # (')( :G6FCL6 6L6 F8=B:9:G
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Contoh 6.4
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89. 8B7:F696996A6B6F
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1
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6F
8B

92. @B
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95. 8BQ

96. PB

97. BG
6L6@:6H6G6L6F8=B:9:G
6F

100. @B

101. BGQ

102. PB

103. )
144 Mudah dan Aktif Belajar Fisika untuk Kelas XI
#
C# P

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6L6 F8=B:9:G )
C B6GG6 ?:CG ;AI96 @B
E:F8:E6H6C F6JH6G BG
JDAIB: ;AI96 L6C 9EC96=@6CJDAIB: 7:C96 L6C H:F8:AIE B
6 7
w air
35 N
50 N
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B6GI@@:96A6BM6H86FB:CL:767@6C7:C9696E6HB:C6EICB:A6L6C
6H6I H:C:A6B
a. Benda Mengapung
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9G:7IHB:C6EIC
6A6B@:6966CC7:F6H7:C966L6@:6H6G96F
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1
#
#
#
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JDAIB: 7:C96 G:AIFI=CL6 B
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C

105. Gambar 6.10
Penyelam dan ikan-ikan
dapat melayang di air.
Tahukah Anda, mengapa
ikan dan penyelam dapat
melayang dalam air?
Ingatlah
Fluida 145
b. Benda Melayang
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H:FG:7IH H96@ G6BE6 B:CL:CHI= 96G6F H67IC B6@6 7:C96 9@6H6@6C
B:A6L6C
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1
#
#
#
#
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?:CG M6H 86F 696A6= G6B6
c. Benda Tenggelam
:C96 H:C:A6B H:F?69 @6F:C6 6L6 7:F6H 7:C96 L6C A:7= 7:G6F
96FE696 6L6 H:@6C @: 6H6G
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1
#
#
#
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86F L6C 9EC96=@6C L6HI 96E6H 9HIAG@6C 76=K6
P
%69?@6B6GG6?:CG7:C96A:7=7:G6F96FE696B6GG6?:CGM6H86F
7:C96 6@6C H:C:A6B
Gambar 6.11
Batu tenggelam dalam air
karena massa jenis batu lebih
besar daripada massa jenis air.
Contoh 6.5
.:7I6=7:C96?@67:F6969I96F67:F6HCL6

106. )
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7:C96H:FG:7IHG:DA6= DA6=B:C?69)
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8BH:CHI@6CA6=
B6GG6?:CG7:C96H:FG:7IH

107. BG
1
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108. ):F6H7:C9696F+6F)
6F

109. @B
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+I96F6P+6F

110. )P))
6L6F8=B:9:G
)

111. @B

112. BG
Q

113. PB

115. 8B
(6GG67:C96
I96F6 +

116. )

117. BG
@

120. G:=C6B6GG6?:CG7:C96696A6=

124. 8B
8B
%69B6GG6?:CG7:C96H:FG:7IH696A6=8B

125. benda fluida mengapung

126. benda fluida melayang

127. benda fluida tenggelam

128. Gambar 6.12
Balon udara merupakan
salah satu penerapan
Hukum Archimedes.
6 7
Gambar 6.13
(a) Hidrometer di dalam raksa.
(b) Hidrometer di dalam air.
Gambar 6.15
B
A
Dua molekul zat cair yang
berbeda posisi memiliki gaya
kohesi yang berbeda.
5. Penerapan Hukum Archimedes
+:C:F6E6C #I@IB F8=B:9:G 96E6H C96 ?IBE6 96A6B @:=9IE6C
G:=6F =6F
DCHD=CL6F6@HE:F6=I@6E6AA6IH96C76ADCI96F6
+69696G6F
CL6 G:BI6 ?:CG @:C96F66C A6IH B:CIC6@6C EFCGE =I@IB F8=B:9:G
696C@6E6A97I6H7:FDC666F96E6HB:BC96=@6CJDAIB:6FA6IHA:7=
7:G6F G:=C6 B6GG6 ?:CG @6E6A B:C?69 A:7= @:8A 96C 6L6 6C@6H DA:=
6F A6IH G:B6@C 7:G6F
6F @:H:F6C6C C 96E6H 9@:H6=I E:CL:767 @6E6A
A6IH L6C B:BA@ B6GG6 G6C6H 7:G6F 96E6H H:F6EIC E696 E:FBI@66C 6F
+FCGE #I@IB F8=B:9:G ?I6 9IC6@6C E696 E:C:F76C6C 76ADC
I96F6
6ADC I96F6 96E6H H:F6C@6H ?@6 B6GG6 ?:CG 96F @:G:AIFI=6C 76ADC
I96F6 H:FG:7IH A:7= @:8A 96FE696 B6GG6 ?:CG I96F6
1DAIB: 6G 96A6B
76ADC I96F6 =6FIG 9E:F7:G6F 6H6I B:CIC6@6C 6G L6C B6GG6 ?:CGCL6
A:7=@:8A96FE696B6GG6?:CGI96F6AI6F66F76ADCH:FG:7IH96E6HH:F6C@6H
:HC6C 76ADC @:H@6 H:F76C 96E6H 96HIF 9:C6C B:C6B76=@6C
6G @: 96A6B 76ADC I96F6
(6GG6 7:76C L6C 96E6H 96C@6H DA:= 76ADC
I96F6 696A6=
146 Mudah dan Aktif Belajar Fisika untuk Kelas XI
I
P
:H:F6C6C
B6GG6 7:C96 @
JDAIB:7:C96B
I B6GG6 ?:CG I96F6 @B
B6GG6 ?:CG 6G @B
#I@IB F8=B:9:G ?I6 9B6C;66H@6C E696 =9FDB:H:F L6HI 6A6H
ICHI@B:CI@IFB6GG6?:CGM6H86F
)- B:CIC?I@@6CG:7I6=
=9FDB:H:FL6CH:F6EIC96A6BM6H86F
1DAIB:=9FDB:H:FG6B69:C6C
JDAIB: M6H 86F L6C 9EC96=@6C DA:= 766C =9FDB:H:F L6C H:F8:AIE
(:A6AI E:FG6B66C =I@IB F8=B:9:G 96E6H 9I@IF B6GG6 ?:CG M6H 86F
H:FG:7IH 9:C6C A6CGIC B:A=6H G@6A6 E696 =9FDB:H:F
6. Tegangan Permukaan
/6=I@6=C96L6C9B6@GI99:C6CH:6C6CE:FBI@66CM6H86F
+:FC6=@6= C96 B:A=6H G:F6C6 L6C 96E6H 7:F?6A6C 9 6H6G 6F
(:C6E6 G:F6C6 H:FG:7IH 96E6H B:A6@I@6CCL6 /:6C6C E:FBI@66C
M6H86FH:F?69@6F:C6696CL6@D=:GL6HI6L6H6F@ B:C6F@6CH6FE6FH@:A
G:?:CG
DCHD=L6CB:C6B76F@6C696CL6H:6C6CE:FBI@66C696A6=
76ADC L6C H:F7I6H 96F 6F G67IC
C96 7G6 B:B7I@H@6CCL6 9:C6C
86F6B:C8:AIE@6C H6C6C C96 @: 96A6B 6F G67IC H:FG:7IH A6AI 7I6HA6=
AC@6F6C 9:C6C ?6F ?:BEDA 96C H:AIC?I@ C96 B6@6 6@6C H:FA=6H 6F
G67IC L6C B:B7:CHI@ 796C 96H6F
+:F=6H@6C)-
6B76FH:FG:7IHB:CIC?I@@6C6L6@D=:G
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(DA:@IAB:C6A6B6L6
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BDA:@IA H:FG:7IH 7:F696 96A6B @:G:B76C6C
:F7:96 9:C6C BDA:@IA
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G6?6
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E:FBI@66C M6H 86F G:E:FH G:A6EIH HEG
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26A6IEIC B6GG6
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H:F6EIC @6F:C6 696CL6 H:6C6C E696 E:FBI@66C 6F
Gambar 6.14
Serangga dapat berjalan di atas
air karena adanya tegangan
permukaan.

129. F
A B
m V
V
A B
w1
w2
Fluida 147
+:F=6H@6C G:?IBA6= H:H:G6C :B7IC E6 L6C ?6HI= 9 6H6G FIBEIH
/:H:G6CH:FG:7IH6@6C7:F7:CHI@G:E:FH7DA6 7DA6@:8A
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P
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G:766 7:F@IH
IG6=6
'
'
AI6G
P
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0CHI@A:7=B:B6
=6B;:CDB:C6H:CH6CH:6C6CE:FBI@66CA6@I@6CA6=@HJH6G!G@6
7:F@IH C
Gambar 6.16
Tetesan air yang jatuh
ke atas rumput.
Pembahasan Soal
Sebuah benda terapung di atas per-mukaan
air yang berlapiskan minyak.
Sebanyak 50 % volume benda berada
di dalam air dan 30 % di dalam minyak.
Jika massa jenis minyak = 0,8 g/cm3
maka massa jenis benda tersebut
adalah ....
a. 0,62 g/cm3
b. 0,68 g/cm3
c. 0,74 g/cm3
d. 0,78 g/cm3
e. 0,82 g/cm3
Soal UMPTN Tahun 1993
Pembahasan:
Benda dalam keadaan setimbang,
maka gaya berat benda sama dengan
gaya angkat Archimedes oleh air dan
minyak.
mbg = FA (air) + FA (minyak)
b b
V g = a a
V g + m m
V g
b
= a
a V
V
b
+ m
b
= (1 g/cm3)(50 %) +
(0,8 g/cm3)(30 %)
= 0,74 g/cm3
Jawaban: c
Aktivitas Fisika 6.2
Tegangan Permukaan
Tujuan Percobaan
Memahami fenomena tegangan permukaan
Alat-Alat Percobaan
1. Panci berisi air
2. Jarum
3. Kertas tisu
4. Minyak pelumas
5. Detergen
Langkah-Langkah Percobaan
1. Ambil jarum yang sudah diolesi minyak pelumas, kemudian simpan jarum
tersebut di atas kertas tisu.
2. Letakkan jarum dan kertas tisu secara perlahan-lahan di atas permukaan air.
3. Amati yang terjadi pada jarum dan kertas tisu tersebut.
4. Taburkan detergen secara perlahan-lahan di sekitar jarum yang terapung,
kemudian amati yang terjadi pada jarum tersebut.
5. Dari hasil Aktivitas Fisika 6.2, lakukanlah diskusi tentang hasil kegiatan tersebut
bersama teman dan guru Fisika Anda. Kemudian, presentasikan hasil diskusi
tersebut.
Gambar 6.17
Tegangan permukaan air sabun
pada kawat.
s
1
2
30 % minyak
50 % air

130. .:76H6C@6K6H97:C@D@@6CG:E:FH=IFI;0
:BI96C
@6K6H@:8A+,L6C7:FB6GG6

131. 9E6G6CE696@6K6H
H:FG:7IHG:E:FHE6966B76F
.:A6C?IHCL6@6K6H @6K6H
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@:8A +, B:C6A6B 6L6 H6F@ @: 6H6G
6F H:F?69
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B6GG6G:7:F6H

132. F6B
%@6E6C?6C@6K6H+,

133. 8B=HICA6=H:6C6CE:FBI@66CA6EG6CG67ICH:FG:7IH
$C6HA6EG6CG67ICB:BA@E:FBI@66CL6HI9:E6C96C7:A6@6C
1
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6L6@:76K6=696A6=
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+@+

134. @7

135. @ 7
air
raksa
148 Mudah dan Aktif Belajar Fisika untuk Kelas XI
@:H6=I
@

136. Q

137. P@

138. Q

139. P@
BG

140. 8B

141. B
(6@69E:FDA:=
@ 7

142. @

143. @ BG

144. B

145. )B
Gambar 6.18
(a) Meniskus cekung
(b) Meniskus cembung
P Q
0,2 gram
Kata Kunci
• gaya Archimedes
• kapilaritas
• melayang
• mengapung
• meniskus cekung
• meniskus cembung
• tegangan permukaan
• tekanan hidrostatik
• tenggelam
Contoh 6.6
Tugas Anda 6.1
Tegangan permukaan dapat dikatakan
sebagai kecenderungan permukaan
zat cair untuk berkontraksi (mengerut).
Menurut Anda, bagaimanakah sifat
tegangan permukaan zat cair ketika zat
cair tersebut dipanaskan?
:H@6 ?6FIB L6C 7:F696 9 6H6G @:FH6G HGI 9 A:H6@@6C G:86F6
E:FA6=6C A6=6C 9 6H6G E:FBI@66C 6F ?6FIB 96C HGI 6K6ACL6 6@6C
H:F6EIC 9 6H6G E:FBI@66C 6F
.:G66H @:BI96C @:FH6G HGI 6@6C
B:CL:F6E 6F G:=C6 B:C?69 76G6= 96C H:C:A6B G:96C@6C ?6FIB
H:H6E H:F6EIC 6@76H 696CL6 H:6C6C E:FBI@66C
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6
FA
F Fk
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Fk
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a. Meniskus Cembung dan Meniskus Cekung
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146. pipa kapiler
air raksa
Gambar 6.19
Gejala kapilaritas pada pipa
kapiler.
cos
A B
y
Gambar 6.20
Pada keadaan setimbang, gaya
tegangan permukaan di titik A
sama dengan di titik B.
Fluida 149
)# L6C H:F?69 @6F:C6 6L6 @D=:G L6C A:7= 7:G6F 96FE696 6L6
69=:G
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147. N
.:76A@CL6 GI9IH @DCH6@ E696 B:CG@IG 8:B7IC 696A6= GI9IH
HIBEIA

148. N
b. Kapilaritas
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1 #
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Tes Kompetensi Subbab A
-'*($!()0'0(/%$*
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150. @B96CHCCL6
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152. 8B
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8B
b
air
air raksa
2,5 cm
B A
6
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154. 8B =6FIG
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156. 8B96CAI6GE:C6BE6C
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158. 8B
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6L6

160. ) 7:F6E6@6= 6L6 L6C 7:@:F?6 E696
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B. Viskositas Fluida
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1. Hukum Stokes
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%@6 7:C96 L6C 7:F:F6@ 96A6B ;AI96 H:FG:7IH 7:F7:CHI@ 7DA6
7:G6FCL6 6L6 .HD@:G 9FIBIG@6C G:766 7:F@IH
(
D:;G:C1G@DGH6GICHI@:F766
(686B!AI96
),-/0-
3
.
6 7
150 Mudah dan Aktif Belajar Fisika untuk Kelas XI
. * P
:H:F6C6C
6L6 .HD@:G )
@D:;G:C JG@DGH6G )GB
?6F ?6F 7DA6 B
* @:8:E6H6C F:A6H; 7DA6 H:F=696E ;AI96 BG
+:F=6H@6C )-
.:7I6= @:A:F:C 9?6HI=@6C 9 96A6B
H67IC L6C 7:FG GI6HI ;AI96
%@6 @:A:F:C H:FG:7IH 9?6HI=@6C @:
96A6BH67ICL6C7:FG;AI969:6A)-
H96@6@6CH:F?69
E:FI76=6CF:GIAH6C6L66@76H:G:@6C;AI96
@6CH:H6E?@6@:A:F:C
9?6HI=@6C @: 96A6B H67IC L6C 7:FG ;AI96 H96@ 9:6A )-
6@6CH:F?69E:FI76=6CF:GIAH6C6L6L6C7:@:F?6
#6AH:FG:7IH
9@6F:C6@6C 696CL6 E:C6FI= 6L6 :G:@6C
Sumber: Physics, 1993
(0%!
F

161. Q

162. P

163. Q

164. P

167. Q

168. P
6F6= Q

169. P
+A6GB696F6=
Q

170. P
H=A6A@D=DA

171. Q

172. P
*A.

174. Q

175. P
AG:FC

177. Q

178. P
096F6

180. Q

181. P
#9FD:C

184. Q

185. P
06E6F

189. Q

190. P
Gambar 6.21
(a) Sebuah kelereng dijatuhkan
ke dalam fluida ideal.
(b) Sebuah kelereng dijatuhkan
ke dalam fluida tak ideal.
.:7I6=76AD@L6CJDAIB:CL6B96CB6GG6?:CGCL6

192. @B 9B6GI@@6C @: 96A6B BCL6@ L6C
B6GG6?:CGCL6

194. @B
6
66B6C6@6=EDGG7:C96
7
#HICJDAIB:7:C96E696E:FBI@66CBCL6@
8
#HIC 6L6 F8=B:9:G L6C 7:@:F?6 E696
7:C96H:FG:7IH

195. FA
Fs
w = mg
Fluida 151
+696 )-
6L6 6L6 L6C 7:@:F?6 E696 @:A:F:C 696A6=
6L67:F6H@:A:F:CL6C9B76CDA:=6L6.HD@:G96C6L6F8=B:9:G
+:CB76C6C6L6H:FG:7IHH:FIG7:FA6C?IHG:FC9:C6C:F6@@:A:F:C
+696G66HH:FH:CHI6L6L6C7:@:F?6G:B76CG:=C6F:GIAH6CG:AIFI=6L6
H:FG:7IH 6@6C G6B6 9:C6C CDA
%@6 7:C96 7:F:F6@ 9:C6C @:8:E6H6C
B6@GBIB L6C H:H6E @:8:E6H6CCL6 C 9G:7IH %(# (#!
.:86F6
B6H:B6HG @:8:E6H6C H:FBC6A 96E6H 9HIFIC@6C 96F FIBIG FIBIG 7:F@IH

196. #PPG

197. G #P P

198. 0CHI@ 6L6 @: 6H6G F8=B:9:G
f #
0CHI@ 6L6 .HD@:G
G *H
:F6H7:C961#
#
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696A6=
(
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P
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7
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f B6GG6 ?:CG ;AI96 @B
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vt @:8:E6H6C H:FBC6A 7:C96 BG
@D:;G:C JG@DGH6G )GB
Contoh 6.7
.:7I6=@:A:F:CL6C7:F?6F ?6F

199. 8B9?6HI=@6C@:96A6BBCL6@E:AIB6GL6C
7:F69696A6BH67IC
/:CHI@6CA6=@:8:E6H6CH:FBC6AL6C986E6@:A:F:C?@6
B6GG6?:CGBCL6@

201. @B@D:;G:CJG@DGH6GBCL6@

202. Q

203. P+6 GB6GG6?:CG
@:A:F:CQ

204. @B96CE:F8:E6H6CF6JH6G

205. BG
1

206. 8BQ

207. PB
bQ

208. @B
f

210. @B

211. BG

212. Q

213. P+6 G
Gambar 6.22
Gaya-gaya yang bekerja pada
kelereng di dalam fluida.
Kata Kunci
• gaya stokes
• kecepatan terminal
• viskositas

214. Tes Kompetensi Subbab B
-'*($!()0'0(/%$*
:8:E6H6CH:FBC6AL6C986E6DA:=G:H:H:GBCL6@
@BL6C?6HI=9I96F6 I96F6
@B 696A6=

215. BBG
#HICA6= ?6F ?6F
H:H:G6CBCL6@H:FG:7IH?@6
Q

216. P@BG
turbulen
laminer
Sumber: Dokumentasi Penerbit
v2
152 Mudah dan Aktif Belajar Fisika untuk Kelas XI

217. B

219. +6 G
#HICA6=@:8:E6H6CB6@GBIB@:8:E6H6CH:FBC6A
96F G:7I6= 7DA6 76?6 7:F96B:H:F BB L6C
9?6HI=@6C96A6BG:?:CGBCL6@
@B
L6CB:BA@@D:;G:CJG@DGH6G
@BRG
(6GG6
?:CG76?6

221. @B
C. Fluida Dinamis
6A6B ;AI96 L6C 7:F:F6@ ;AI96 9C6BG G:H6E E6FH@:A E696
;AI96 H:FG:7IH B:BA@ @:8:E6H6C ICHI@ G:H6E EDGGCL6
*A:= @6F:C6
HI ;AI96 9C6BG 96E6H 96B76F@6C G:766 B:96C @:8:E6H6C *
%@6 ACH6G6C E6FH@:A HH@ E696 ;AI96 96B76F@6C 6@6C 9E:FDA:=
GI6HI ACH6G6C L6C 9C6B6@6C 6FG 6AF6C
6A6B ;AI96 9C6BG 696 9I6
6FG 6AF6C L6HI !# !# 96C !# ())!#
AF6C A6BC:F 696A6=
6AF6C ;AI96 L6C @:8:E6H6C 6AF6C E696 G:H6E HH@ E696 ;AI96 H:FG:7IH
H96@7:FI76=H:F=696EK6@HI
96EIC6AF6CHIF7IA:C696A6=6AF6C;AI96
L6C @:8:E6H6C 6AF6C G:H6E HH@ E696 ;AI96 H:FG:7IH 96E6H 7:FI76=
)-
B:C6B76F@6C 6AF6C 6G6E FD@D@
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96EIC 6G6E E696 766C
6H6G 7:FEIH6F EIH6F 96C G:H:FIGCL6 B:CL:76F @: G:6A6 6F6=
AF6C
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+:F=6H@6C )-

222. +696 6B76F H:FG:7IH 9AI@G@6C :BE6H
6FG 6AF6C E6FH@:A E6FH@:A ;AI96
+6FH@:A E6FH@:A ;AI96 E696 G:H6E
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6FG6AF6CL6CA6C
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L6C G6B6 ?I6 H96@ 696 6L6 :G:@ 6CH6F6 A6EG6C 6AF6C ;AI96 L6C
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B:G@EIC 696 H:@6C6C
1. Persamaan Kontinuitas
+:F=6H@6C)-
+6966B76FH:FG:7IHM6H86FB:A6AIG:7I6=
EE6E696E:C6BE6C
9:C6C@:8:E6H6C6AF6C*
B:CI?I@:E:C6BE6C
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?IBA6= M6H 86F L6C B:C6AF B:A6AI E:C6BE6C
6@6C G6B6 9:C6C
?IBA6= M6H 86F L6C B:C6AF B:A6AI E:C6BE6C
1DAIB: M6H 86F E696
E:C6BE6C
G6B6 9:C6C JDAIB: M6H 86F E696 E:C6BE6C
Gambar 6.23
Aliran laminer dan aliran
turbulen pada asap rokok.
*H
Q

223. BGQ

225. @BP

227. @B
BG
%69@:8:E6H6CH:FBC6A@:A:F:C696A6=BG
Gambar 6.24
Garis aliran A–B–C, D–E–F,
P–Q–R, dan X–Y–Z merupakan
garis aliran laminer.
A
D
P
X
B
E
Q
Y
CF
R
Z
v1
A1
A2
s1
s2
Gambar 6.25
Fluida mengalir pada
penampang yang berbeda.

228. Ingatlah
Informasi
untuk Anda
Information for You
Fluida 153
'
'
*
( * (
0CHI@ G:A6C K6@HI L6C G6B6 6@6C 9E:FDA:=
*
* P
.:7I6=EE6L6CAI6GE:C6BE6CCL6
8B96C
8B96AF6F
+696E:C6BE6CL6C
7:G6FA6?I6AF6C6FCL6696A6=BG
:F6E6@6=A6?I6AF6C6FE696E:C6BE6CL6C@:8A
1
@:H6=I
8B
Q

229. PB
8B
Q

230. PB
*
BG
:C6CB:CIC6@6CE:FG6B66C9:7H6F9E:FDA:=
*
*

231. QBGBG
6H6I
P
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B
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*
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BG
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*
9:7HM6H86F9E:C6BE6C
BG
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-.)* 4

232. 96C -.)* 4
9C6B6@6C %'#
$#(#)('
Contoh 6.8
Aktivitas Fisika 6.3
Persamaan Kontinuitas
Tujuan Percobaan
Mengamati dan memahami persamaan kontinuitas
Alat-Alat Percobaan
1. Dua buah selang yang berdiameter 1 cm atau lebih dengan panjang masing-masing
2 meter
2. Dua buah ember
3. Plastik tebal.
Langkah-Langkah Percobaan
1. Tutuplah salah satu ujung selang dengan plastik tebal yang telah dilubangi.
Diameter lubang plastik ±0,5 cm.
2. Sambungkan kedua selang pada kran yang aliran airnya sama besar.
3. Jawablah pertanyaan berikut.
a. Untuk posisi kedua selang sama, semburan air pada selang manakah yang
paling jauh?
b. Apa yang akan terjadi jika dalam selang waktu yang sama, setiap air selang
dialirkan pada ember yang berukuran sama?
4. Tulislah kesimpulan dari percobaan tersebut.
5. Buatlah Hukum Kontinuitas menurut versi Anda berdasarkan percobaan yang
telah Anda lakukan.
6. Bandingkan dengan Hukum Kontinuitas yang sudah Anda pelajari.
Prinsip utama dari persamaan
kontinuitas adalah pada selang
waktu yang sama, debit fluida akan
sama.
Seorang penyelam pemula sedang
menarik napas pada kedalaman L
untuk berenang ke atas. Dia
mengabaikan instruksi untuk
mengeluarkan napas secara perlahan-lahan
selama menuju ke permukaan.
Selama perjalanan ke atas, tekanan
udara luar pada tubuhnya berkurang
hingga mencapai tekanan atmosfer.
Tekanan darahnya juga berkurang
sampai normal kembali. Oleh karena ia
tidak membuang napas, ketika sampai
ke permukaan terdapat perbedaan
antara tekanan udara di dadanya
dengan di dalam paru-parunya.
Perbedaan tekanan ini dapat
mengakibatkan paru-parunya pecah.
Selain itu, tekanan darahnya turun
drastis sehingga udara pun masuk ke
dalam jantungnya. Hal ini dapat
mengakibatkan kematian bagi
penyelam tersebut.
A novice scuba diver takes enough air
from his tank to fully expand his lung
at depth L and swimming to the
surface. He ignores instructions and
fails to exhale during his ascent. As he
ascends, the external pressure on him
decreases, until it reaches the
atmosphere pressure at the surface. His
blood pressure also decreases, until it
become normal again. However,
because he does not exhale the air
pressure in his lungs remain at the
value it had at depth L. This pressure
difference can explode his lungs.
Besides that, his blood pressure
decrease drastically which then
carries the air to the heart. This two
things can kill that novice diver.
Sumber: Fundamentals of Physics, 2001

233. 2. Hukum Bernoulli
+696 7:?6C6 7:F=I7IC6C E:FBI@66C M6H 86F E696 G:H6E H:BE6H
6@6C G6B6 HC
#6A H:FG:7IH 7:FA6@I E696 M6H 86F L6C 96B
%69
?@6 M6H 86F H:FG:7IH 7:F:F6@ @:6966C H:FG:7IH H96@ 6@6C H:F?69
+:F=6H@6C )-
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B6@6 HC E:FBI@66C M6H 86F E696 EE6 EE6 96C EE6 6@6C
G6B6
)6BIC HC E:FBI@66C M6H 86F E696 G:H6E EE6 6@6C 7:F7:96
?@6 M6H 86F H:FG:7IH B:C6AF @: @6C6C
C96 H:A6= B:C:H6=I 76=K6 @:A6?I6C M6H 86F E6AC 7:G6F H:F96E6H
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.:86F6B6H:B6HGE:FG6B66CL6CB:C6B76F@6C6AF6C;AI96E696
6B76F H:FG:7IH 696A6=
C
Gambar 6.26
Fluida mengalir.
Gambar 6.27
B
Perbedaan ketinggian fluida
mengalir.
Sumber: World Book Encyclopedia
A
v
154 Mudah dan Aktif Belajar Fisika untuk Kelas XI
)' -/
'
% *( P
0G6=6 HDH6A L6C 9IC6@6C ICHI@ B:C6AF@6C ;AI96 96F @:6966C
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234. P

235. %
%
*
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9G:7IH ?I6 '#
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Tokoh
Daniel Bernoulli
(1700–1782)
Daniel Bernoulli adalah putra dari
Johan Bernoulli, lahir di kota Basel
dan bekerja sebagai dosen
Matematika di Universitas Basel.
Pamannya seorang matematikawan
di Universitas tersebut yang pernah
menciptakan materi baru dalam
teori probabilitas, analisis geometri,
dan kalkulus variasi. Bernoulli
berhasil menciptakan prinsip
hidrodinamika dan perhitungan
aliran fluida. Selain itu, Bernoulli
sangat berperan dalam
mengembangkan teori probabilitas,
kalkulus, dan persamaan diferensial.
p1
A1
h1
p2
h2
v1 t
v2 t

236. pipa venturi
gaya angkat (F1)
gaya berat (F2)
Fluida 155
%
*
@DCGH6C P

237. :F96G6F@6CE:FG6B66C:FCDIAA9@:H6=I76=K6H:@6C6C996A6B
;AI96 L6C 7:F:F6@ 9E:C6FI= DA:= @:8:E6H6C 6AF6C ;AI96 H:FG:7IH
3. Penerapan Hukum Bernoulli
a. Alat Penyemprot Nyamuk
+:F=6H@6CA6= )-
L6C B:BE:FA=6H@6C G:7I6= 6A6H
E:CL:BEFDH CL6BI@
A6H H:FG:7IH B:CIC6@6C EFCGE #I@IB
:FCDIAA
%@6 E:CG6E EDBE6 9H:@6C I96F6 6@6C B:C6AF 9:C6C
@:8:E6H6C HC 96C @:AI6F B:A6AI AI76C G:BEH E696 H67IC I96F6
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J:CHIFB:C?69F:C96=
#6AH:FG:7IHB:CL:767@6C86F6CD76HCL6BI@96E6H
C6@ @: 6H6G B:A6AI EE6 J:CHIF 96C B:CL:B7IF @:AI6F 7:F86BEIF I96F6
b. Daya Angkat pada Sayap Pesawat Terbang
/6=I@6= C96 L6C B:CL:767@6C E:G6K6H 96E6H H:F76C +:G6K6H
96E6H H:F76C @6F:C6 696CL6 96L6 6C@6H E696 G6L6E
6L6 6C@6H E696
E:G6K6HH:F76C?I6B:CIC6@6CEFCGE#I@IB:FCDIAA
:CHI@766C
6H6GG6L6EE:G6K6HL6C8:B7ICB:CL:767@6C696CL6E:F7:966CA6?II96F6
E696 766C 6H6G 96C 766C 76K6=CL6 G:E:FH 96B76F@6C DA:= 6FG 6FG
6L6 E696 )-
AF6C I96F6 E696 766C 6H6G G6L6E 7:F:F6@ A:7=
8:E6H 96FE696 766C 76K6=CL6
(:CIFIH #I@IB :FCDIAA H:@6C6C E696
766C 6H6G E:G6K6H B:C?69 A:7= @:8A 96FE696 H:@6C6C E696 766C 76K6=
G6L6E
+:F7:966C H:@6C6C CA6= L6C B:B7I6H 696CL6 6L6 6C@6H @: 6H6G
L6C 7:G6FCL6 96E6H 9HIAG@6C G:766 7:F@IH
P
%
P %
P
*
P
*
P
*
P*
P
:F96G6F@6C-.)*4 96E6H96C6AGG76=K6?@6E:G6K6H
7:F:F6@ A:7= 8:E6H B6@6 6@6C B:C=6GA@6C 6L6 6C@6H L6C A:7=
7:G6F EIA6
:C6C 9:B@6C G:B6@C AI6G E:C6BE6C G6L6E G:B6@C
7:G6F EIA6 6L6 6C@6HCL6
Contoh 6.9
.:7I6=E:G6K6HH:F76C9:C6CAI6GE:C6BE6CG6L6E

238. B7:F:F6@G:=C6
B:C=6GA@6CE:F7:966C@:8:E6H6C6AF6CI96F6E696766C6H6GG6L6EE:G6K6H96C
766C76K6=CL6L6CB6GC B6GC7:G6FCL6

239. BG96C

241. BG
:F6E6@6=
7:G6F6L66C@6HE696G6L6E?@6B6GG6?:CGI96F6
@B
1
@:H6=I

242. B*

243. BG
*

245. BG
@B
P
* *
Q
@BQ

246. BQ4

247. BGP

249. BG5

251. )
%696L66C@6HE696G6L6EE:G6K6HH:FG:7IH696A6=

253. )
F
Gambar 6.28
Alat penyemprot nyamuk.
Gambar 6.29
Garis arus fluida ideal pada sayap
pesawat terbang.

254. c. Karburator
6F7IF6HDF B:FIE6@6C 6A6H E:C86BEIF 76=6C 76@6F 96C I96F6
+:C86BEIF6C H:FG:7IH 7:FHI?I6C ICHI@ B:BE:FBI96= E:B76@6F6C
6F7IF6HDF H:F9F 6H6G H6C@ @6F7IF6HDF E:A6BEIC EE6 J:CHIF 96C
E:CL:BEFDH I96F6 #$.!
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d. Pipa Venturi
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=6FIG 9A:H6@@6C B:C96H6F G:=C6
:C6C B:CIC6@6C
=I@IB :FCDIAA 9E:FDA:=
h
Gambar 6.30
Karburator pada motor.
156 Mudah dan Aktif Belajar Fisika untuk Kelas XI
% % * * P
6F E:FG6B66C @DCHCIH6G 9E:FDA:=
*
P
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255. 9E:FDA:=
*
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E:F7:966C HC F6@G6 B
E:F8:E6H6C F6JH6G BG
p1 v1 p2 v2
h2 h1
Gambar 6.31
Pipa venturi.
karburator
Sumber: www.firetrucks.uw.hu

256. .1 .2
v1 v2
B
2
Fluida 157
e. Venturimeter dengan Manometer
)-
B:CIC?I@@6CJ:CHIFB:H:FL6C9A:C@6EB6CDB:H:F
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A
Gambar 6.32
Venturimeter yang dilengkapi
manometer.
v2
h
C D
aliran gas
A
v1
p1
Gambar 6.33
Pipa pitot
h
B
tekanan tinggi
tekanan rendah
1

257. Tes Kompetensi Subbab C
-'*($!()0'0(/%$*
158 Mudah dan Aktif Belajar Fisika untuk Kelas XI
% * %
% % * P

258. :96H:@6C6C6CH6F6HH@
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% % P
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259. @:-.)*4

260. 9E:FDA:=
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* P
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E:F7:966C HC 6F F6@G6 B
:F6HG:7I6=E:G6K6HL6CB:BA@AI6GHDH6AG6L6E

261. B696A6=

264. )
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766C 76K6= G6L6E

265. BG
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H:FG:7IH

266. 8B#HIC76CL6@CL66FL6C96E6H
9H6BEIC96A6BK6@HI
?6B
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@:8:E6H6C6AF6CI96F696H6G96C976K6=G6L6E

267. BG96C

268. BG(6GG6?:CGI96F6E696@:HC6C
HI
@B
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270. 8B 96C

271. 8B
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272. 8BG
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8BE696B6CDB:H:F
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@:8A696A6=
Kata Kunci
• aliran turbulen
• aliran laminer
• hukum Bernoulli
• manometer
• persamaan kontinuitas
• venturimeter

273. Fluida 159
Rangkuman
/:@6C6CB:FIE6@6C7:G6F6L6L6C7:@:F?6E696
GI6HIE:FBI@66C9769:C6CAI6G6L6
,
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(
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J:CHIFB:H:F9:C6CB6CDB:H:F96C
;
EE6EHDH

274. B:B76=6G 96C6E
Refleksi
B:B76=6G
Setelah mempelajari bab ini, Anda tentu dapat
mengetahui konsep tekanan pada zat cair, hukum-hukum
yang berlaku baik pada zat cair yang diam maupun pada
zat cair yang bergerak. Dari materi-materi yang ada pada
bab ini, bagian manakah yang menurut Anda paling sulit
160 Mudah dan Aktif Belajar Fisika untuk Kelas XI
dipahami? Coba Anda diskusikan dengan teman atau
guru Fisika Anda.
Dalam bab ini, dijelaskan pula beberapa manfaat
dari konsep yang dibahas. Coba sebutkan manfaat yang
Anda peroleh setelah mempelajari materi pada bab ini.
Peta Konsep
(0%!
!AI96.H6HG !AI96C6BG
/:@6C6C#9FDGH6HG
#I@IBF8=B:9:G
/:6C6C+:FBI@66C
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!AI96$9:6A
+:FG6B66CDCHCIH6G
+:FG6B66C:FCDIAA
O 6L6C@6H+:G6K6H
O /67IC1:CHIF
O +E6+HDH
+:FG6B66C1G@DGH6G
B:C=6GA@6C
96EA@6G@6C E696

275. Fluida 161
%(%$($.($./01*2*#,(%*#/,/!*'-'*($,!0'0(/%$*
.:@:EC B6H6 I6C AD6B ?@6 98:AIE@6C 96A6B
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A

276. 8BB:C6A6B6L6@:
6H6GG:7:G6F
%@698:AIE@6C96A6B;AI96
9:C6C
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277. 8BB:C6A6B6L6F8=B:9:GG:7:G6F
+:F76C9C6C@:9I66L6H:FG:7IHL6HI
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6

279. @B 9

282. @B
7

284. @B :

286. @B
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287. @B
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288. 8BG:=C6E:F7:966CE:FBI@66C6FF6@G6
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289. 8B
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290. 8B
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291. 8B
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294. 8B696A6=
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297. )B96CB6GG6
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299. @BE6C?6C,
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300. B 9

301. B
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302. B :
B
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303. B
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6

325. 8B 9
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8B :

327. 8B
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329. 8B
1 m x
P
45 cm
v A1 A2
h
v1
P1
v2 P2
Tes Kompetensi Bab 6

330. .:7I6= AD6B 7:F7:CHI@ 7DA6 7:F?6F ?6F

331. 8B
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339. @B96C@D:;G:CJG@DGH6GI96F6

340. Q

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343. PB 9
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344. PB
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346. PB
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347. PB
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162 Mudah dan Aktif Belajar Fisika untuk Kelas XI
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