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FLUID STATICSDr. Novia ST., MT.NIP. 19731105 200003 2003

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The application of Newton’s law of motion

can be applied to uid at rest

F ! m " a

For a simple uid at rest# the pressure is

the same in all directions There are no shear stress in a uid at rest

Introduction

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Consider a small bloc$ of uid that is part ofa lar%e mass of uid at rest in a %ra&it'(eld"

Since the uid is at rest# there are are noaccelerations# and the sums of the force onan' part of the uid in an' direction is )ero"

The *asic +,uation of FluidStatics

 ∆y

z=0

z= ∆z

 ∆z

 ∆x

z y

x

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Considr !" z dir#!ion, o$$osi! !o !"dir#!ion o% &ravi!y.

 T" %or#s !"a! a#! on !" s'a(( )(o#* o%+id in !" z dir#!ion ar !" $rssr%or#s on !" !o$ and )o!!o'- and !" %or#o% &ravi!y a#!in& on !" 'ass o% ('n!.

 T"ir s' is

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Dividin& /x /y /z, &iv

i'i! !o /z a$$roa#" zro

*A-./+T-IC +0UATI.N

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Ideal 3ases

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2-+SSU-+ F.-C+S .NSU-FAC+S

2ressure 4 Surfacearea ! constant

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*U.5ANC5 

"

y

x

z

(oa!in& )(o#* o% 4ood

*uo'ant Force6 The &erticalcomponent of thepressure force

inte%rated around theentire sureface of aoatin% bod'7

Cos 8 !9 top: !19  bottom

(

Di'ana

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Prssr sa((y ar 'asrd )y (!!in&!"' a#! a#ross so' ara and o$$osin&

!"' 4i!" i!"r &ravi!y %or# or !" %or#o% a #'$rssd s$rin&

ravi!y6%or# '!"od Mano'!r

2-+SSU-+ /+ASU-+/+NT

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/anometer is open to the atmosfer at A

3AS D

C

*

A ; ft

9 ft

9

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r:a*an soa( 2.17 ; 2.39, 2.

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-+F+-+NC+S

1. C. . an*o$(is, Trans$or! Pro#ss and >ni!?$ra!ions, @disi *63, Prn!i#6Aa((, In#.,@n&(4ood C(iBs, N4 rsy, 1993

2. . . Ao((and dan . ra&&, (id (o4 %or C"'i#a(@n&inrs, @disi *62, @d4ard rno(d, ondon, 1995

3. . . M#Ca), . C. S'i!" dan P. Aarrio!, >ni!?$ra!ions o% C"'i#a( @n&inrin&, @disi *65,M#ra46Ai(( oo* Co. In#., N4 Eor*, 1993