Post on 06-Jul-2018
8/17/2019 3.2 Understanding Pressure in Liquid
1/16
PHYSICS FORM 4PHYSICS FORM 4
20142014
8/17/2019 3.2 Understanding Pressure in Liquid
2/16
Pressure in liquid acts in allPressure in liquid acts in all
directionsdirections
http://rds.yahoo.com/_ylt=A0Je5m1_IJBEtlYABGuJzbkF;_ylu=X3oDMTBjcXBoZjEwBHBvcwMzBHNlYwNzcg--/SIG=1hi6fojg2/EXP=1150382591/**http%3A//images.search.yahoo.com/search/images/view%3Fback=http%253A%252F%252Fimages.search.yahoo.com%252Fsearch%252Fimages%253Fp%253Ddiver%2526fr%253DFP-tab-img-t-t400%2526toggle%253D1%2526cop%253D%2526ei%253DUTF-8%26w=750%26h=563%26imgurl=www.rummelraiders.com%252Fwebbies%252Fcmire%252Fcayman05%252Fdivers%252Fimages%252Fdiver_07.jpg%26rurl=http%253A%252F%252Fwww.rummelraiders.com%252Fwebbies%252Fcmire%252Fcayman05%252Fdivers%252Fpages%252Fdiver_07.htm%26size=49.5kB%26name=diver_07.jpg%26p=diver%26type=jpeg%26no=3%26tt=401,334%26ei=UTF-8
8/17/2019 3.2 Understanding Pressure in Liquid
3/16
Static Fluid PressureStatic Fluid Pressure
The pressure eerted !" a staticThe pressure eerted !" a static
#luid depends onl" upon the#luid depends onl" upon the
depthdepth o# the #luid$ theo# the #luid$ the densit"densit" o#o#
the #luid$ and thethe #luid$ and the acceleration o#acceleration o#
%ra&it"'%ra&it"'
8/17/2019 3.2 Understanding Pressure in Liquid
4/16
Colu(n o# liquid
Sur#ace area$ )
h
*ensit" o# liquid$ + ,%(-.
/ase sur#ace area$ ) (2
*epth$ h (
The colu(n o# liquid eerts a pressure
on the !ase due to its ei%ht
olu(e o# liquid ) h (eter cu!e 3(
.
Mass o# liquid ) h + ,ilo%ra( 3,%
5ei%ht o# liquid ) h + % 6eton 36
Pressure in liquid P = weight of liquid / surface area
= A h ρ g / A
= h ρ g
8/17/2019 3.2 Understanding Pressure in Liquid
5/16
7 The pressure at any point in a liquid
acts equally in all directionsPress
ure in liquid$ P hρ%
h depth o# the liquid
ρ densit" o# theliquid
% %ra&itational #ield
stren%th
8/17/2019 3.2 Understanding Pressure in Liquid
6/16
Pressure at an" point in a liquid isPressure at an" point in a liquid is
due to thedue to the weight of wei
ght of the liquidthe li
quid
above that point above that
point ''
)t the )t the same level same level oror depthd
epth$ the$ the
liquid pressure (ust !eliquid pressure (ust !e thethe samesame$$
h h
P Q
8/17/2019 3.2 Understanding Pressure in Liquid
7/16
) hu%e (etal tan, is used to store a certain ) hu%e (etal tan, is used to store a certain
t"pe o# oil' 5hat is the pressure eerted !"t"pe o# oil' 5hat is the pressure eerted !"
the oil at a depth o# .'8 ( i# the densit" o#the oil at a depth o# .'8 ( i# the densit" o#
the oil is 940 ,%(the oil is 940 ,%(-.-. and % is :'9 6,%and % is :'9 6,%-1'-1'
P h ρ g
= 3.5 x 840 x 9.8
= 8!8" Pa
7#ther exa$%les& 'ext (oo) %age **+*8
7, ho$ewor) fro$ text(oo)& 3. questions! no."! ! - 3 %age *8.
8/17/2019 3.2 Understanding Pressure in Liquid
8/16
)pplications o# pressure in liquids )pplications o# pressure in liquids
Thic,ness o# o# alls o# si((in% pools$ da(sThic,ness o# o# alls o# si((in% pools$ da(s
Window ofWindow of
submarines /submarines /
aquariumsaquariums
http://rds.yahoo.com/_ylt=A9iby4bGLJBE9R0BzweJzbkF;_ylu=X3oDMTBjZmpxdmw3BHBvcwM3BHNlYwNzcg--/SIG=1flap0upo/EXP=1150385734/**http%3A//images.search.yahoo.com/search/images/view%3Fback=http%253A%252F%252Fimages.search.yahoo.com%252Fsearch%252Fimages%253Fp%253Dwall%252Bof%252Bdams%2526ei%253DUTF-8%2526fr%253DFP-tab-img-t-t400%2526x%253Dwrt%26w=326%26h=241%26imgurl=www.esk.qld.gov.au%252Fimages%252Ftourism_somersetdam_wall.jpg%26rurl=http%253A%252F%252Fwww.esk.qld.gov.au%252Fdams_%2526_rivers.htm%26size=11.8kB%26name=tourism_somersetdam_wall.jpg%26p=wall%2Bof%2Bdams%26type=jpeg%26no=7%26tt=112%26ei=UTF-8http://rds.yahoo.com/_ylt=A9ibyiAXLZBEi0kAHNOJzbkF;_ylu=X3oDMTBkdjI4bXVrBHBvcwMyNARzZWMDc3I-/SIG=1eh3qc7ka/EXP=1150385815/**http%3A//images.search.yahoo.com/search/images/view%3Fback=http%253A%252F%252Fimages.search.yahoo.com%252Fsearch%252Fimages%253Fp%253Daquariums%2526ei%253DUTF-8%2526fr%253DFP-tab-img-t-t400%2526b%253D21%26w=340%26h=241%26imgurl=www.aquionics.com.au%252Fgraphics%252Fcom_aqua.jpg%26rurl=http%253A%252F%252Fwww.aquionics.com.au%252Fproducts%252Fcom_aqua.html%26size=14.7kB%26name=com_aqua.jpg%26p=aquariums%26type=jpeg%26no=24%26tt=60,237%26ei=UTF-8
8/17/2019 3.2 Understanding Pressure in Liquid
9/16
Constructions of deep-Constructions of deep-
sea exploring vehiclessea exploring vehicles
*i&ers suit*i&ers suit
http://rds.yahoo.com/_ylt=A9iby4aTLJBEShwBsbeJzbkF;_ylu=X3oDMTBkdjU2cm9hBHBvcwMyMQRzZWMDc3I-/SIG=1fe13g74g/EXP=1150385683/**http%3A//images.search.yahoo.com/search/images/view%3Fback=http%253A%252F%252Fimages.search.yahoo.com%252Fsearch%252Fimages%253Fp%253Ddiver%252Bsuit%2526ei%253DUTF-8%2526fr%253DFP-tab-img-t-t400%2526b%253D21%26w=300%26h=451%26imgurl=www.history.ky.gov%252FKHS_Images%252Fsuit1_b%2526w300.jpg%26rurl=http%253A%252F%252Fwww.history.ky.gov%252FAbout_KHS%252FKHS_News_Hardin_aame.htm%26size=24.6kB%26name=suit1_b%26w300.jpg%26p=diver%2Bsuit%26type=jpeg%26no=21%26tt=961%26ei=UTF-8
8/17/2019 3.2 Understanding Pressure in Liquid
10/16
;plain h" the alu(iniu( can;plain h" the alu(iniu( can
cru(ples hen it is !rou%ht tocru(ples hen it is !rou%ht to
the ocean #loor !ut$the ocean #loor !ut$
It does not cru(ple i# a #eIt does not cru(ple i# a #e
holes are (ade on the canholes are (ade on the can
8/17/2019 3.2 Understanding Pressure in Liquid
11/16
;%'
1' )n air !u!!le is a depth o# . (!elo the sur#ace o# a la,e'
a' 5hat is the pressure o# ater on the
air !u!!le<
3densit" o# ater$ ρ 1000 ,% (+3
P hρ%
------------
!'Calculate the air pressure i# the!u!!le in the sea<
3densit" o# sea ater$ ρ 1280 ,% (-.
)nser=
8/17/2019 3.2 Understanding Pressure in Liquid
12/16
)pplications o# Pressure in )pplications o# Pressure in
>iquids>iquids
Pu!lic ater suppl" s"ste(Pu!lic ater suppl" s"ste(
a'a' The ater is pu(ped up to a aterThe ater is pu(ped up to a ater
stora%e tan, situated hi%her than allstora%e tan, situated hi%her than all
the houses in that area'the houses in that area'
*ue to %ra&itational pull$ ater in the*ue to %ra&itational pull$ ater in thestora%e tan, is (aintained at hi%h pressurestora%e tan, is (aintained at hi%h pressureand this ena!les ater to #lo to theand this ena!les ater to #lo to thehouses o# the consu(ers hich are loer'houses o# the consu(ers hich are loer'
!'!' Fire hose used !" a Fire Fi%hter Fire hose used !" a Fire Fi%hter c'c' The alls o# a da(The alls o# a da(
8/17/2019 3.2 Understanding Pressure in Liquid
13/16
2' The #i%ure shos a da( ith a depth o# 28 (2' The #i%ure shos a da( ith a depth o# 28 (allater allater
a'a' Calculate the ater pressure at theCalculate the ater pressure at the
!otto( o# the da( hen the ater is at!otto( o# the da( hen the ater is at
the (ai(u( le&el
8/17/2019 3.2 Understanding Pressure in Liquid
14/16
ConclusionConclusion
1.1. Pressure in liquid,Pressure in liquid, P P == hh ρ ρ g g
2.2. Liquid PressureLiquid Pressure
i.i. at the same depth actsat the same depth actsequally in all directionsequally in all directions
ii.ii. increases with depthincreases with depth
iii.iii. increases with densityincreases with density
iv.iv. increases with gravitationalincreases with gravitationalstrengthstrength
8/17/2019 3.2 Understanding Pressure in Liquid
15/16
6et class = prepare #or the6et class = prepare #or the
topic=topic=
?)S PR;SS@R; )6*?)S PR;SS@R; )6*
)TMOSPH;RIC PR;SS@R; )TMOSPH;RIC PR;SS@R;
8/17/2019 3.2 Understanding Pressure in Liquid
16/16
'A 1#2
A A 67 A1