Physics Energy and Waves Class Notes

, Week 1 :S t a t i c fluids reading
I




phases states
-
of matter:



solias:definite shape, specific volume



liquids:definite volume, shape depends on container



gases:n e it h e r a definite shape for specific vo l u m e , molecules move to fill container
they are in



plasmas:neither definite shape nor wome




density:

per unit
v olume of substance
density object
is the mass a
or




defined as 1 *,
=



=density, m m a ss , V
=




volume,
=




units
vg/m3
=




Swater 19/cm3 =
100
=




kg/m3

of
density reveals phase st r u c t u re : density gases (liquids solids
+
+




pressure:


p E, F force applied to an A a re a thati s perpendicular to the force, units 1Pa =I N ma
=




pressure, area,
= -



P
=



=




WO mb (millibar) 1
=



x
10
4
Pa


fluid pressure has no direction:s c a l a r quantity

forces due to defined directions: perpendicular
pressure have well
always exerted to a surface


RO2



4 round
c1kg, legs dieg
=



m 4.8 c m
=




C) pressure each
leg exerts on carpet

41kg
=
4 =




1.2549/leg
F 10.25kg 9.8 MIS2 wo.4 5 N
=




mg
=
x
=




m2
M(2.4 100) 0.0018096
=

Acrae 12
=
=
=




p E
=
=


2
06 55510.8 pa
=




four
b) total pressure on the carpet
by all
legs

4 1 9.8 401.8N
=




F mg
=




C11kg
=
=



m =




A
=
Mr2 i(2.4 w0)2
=
=
0.0 0 1 8 0 9 6 m r
=




E 618096
=




p 5 5 5 0 9.5
=



=




pressure depth
+




p M
=




P pressure,
=

m mass,
=




g gravity,
=
A a re a
=




supporting
v vo l u m e
m eV, 2
density,
=




mass,
=




m
=
=




V A U,
=



v vo l u m e ,
=
c ross-sectional
A: area, U=depth



m e
=


An


p eA19
=




- > p =heg/pressure are to the weighto f any fluid)

atmospheric pressure:


1atmosphere (atm) Pa t m =



1.0 1
=


1 0 5 N/m2 l o1 k Pa
=




favg ig =




n g
=




pascal's principle:


force
pressure: per unita re a



Pascal's Principle:a change in pressure applied an
to enclosed said is transmitted undiminished to all portions of the fluid and to the walls of its container



hydraulic systems:p , P2, =

E =
work:f orce times distance moved
1100 49

⑤
R05 de 20d,
=




m 1160
=




bg d -zoc
i((2001) 2)2
9.8
Fz 1 1 6 0
=
=




Az
=
=




F211368 N
=

, *
z

-
168
F1 =




F1
=
2842
= =
100 28.4N
=




gauge pressure, absolute pressure, and pressure measurement



for it
garge pressure pressure
-

relative atmospheric
to
pressure positive for pressures above atmospheric pressure, and negative values below



absolute pressure:t h e of
atmospheric
sum
garge pressure and pressure



Pabs Pg =

+


Patm


in
* cases fluids
most absolute pressure of cannotb e negative

↳ smallesta bsolute pressure is 0, pulling --, pushing t



LD
Pg = -Patm (smahest)

manometer:U-shaped tube, both ends open to atmosphere (pressure pushes down on both sides
equally concerning out
it



Lo pressure
deeper on one side:
greater

↳is one side open
(Pg=egh)
to atm: ideal for measuring Page

1.0mmHg (millimetres mercury) 1 3 3 Pa
=




systolic pressure:maximum blood pressure


diastolic pressure:m i n i m u m blood pressure



example 11.7:



ff1 1.0g/mL
=




n?=




Paarge 18
mmHg 13342 239446
=



= =




Pg e 9 h
=




2394
100kg12 9.8 M/S2 h
=

=
=




h 0.244m
=




barometer:device thatm easures atmospheric pressure




Week 1 :Lec ture questions




L 1.1 :
Density

1) T
D
-



o

2) ice X



3)
*ice 11 mice m re a d =




> Me
a) rank
highestt o m a ss
lowest
M3
M1=




b) V 3 >Ve = V,
rank from highestt o
lowestvolume:




C) rank from highestt o
lowest
density:11782=13




11.2 water
density
One litre (= rocm = re m x wa m
100cm3)
=

of water has m=
lky

a) density of water in
ag,m3: 10o
bgim?


b) density of water in
glans:Iglan3

, 11.3 safe
Density a
of




Lorter = 1.2m




(thickness 4 a n
=




0.0 4
=


m




a) density of metal safe metal=7870 kg/m3
average

Linner -(0.04 x2) 1.1 2 m
=



1.2
=




Vinner (1.12)3
=

1.4 0 5 m3
=




Usage (1.2)
=
=
1.728m3


Parg mmair-Mrsafe-voir
=




Prietal (Usafe-Vair)
Parg
=




-
r safe



7870 yy1m3 =
(1728 1.405)
-




Parg
=




1.728



Parg 1471.1 Ug1M3
=




b) World the safe float?N o , itw i l l sinn because the
density is
greater than thato f water




11.4 Pressure

--




-
a)

I A
all
D




rank the pressures exerted
by the block:4a)Pb>4c




21.8 Uniform connected fluids




it---.* Im
P, Patm
=


Di P2
=




P, Patm =




+egh

P, W 1 0 0
=


1000
+

9.8
= 0.6 m
x




Pa 2 07.2
P, 207180 uPa
=
=




21.9 measuring gas pressure with a
mercury manometer



frg 13.6 g/m2
=




10
=




↳Iam
Pgas Patm
=



-fgU

Pgas 101300Pa-13.6 20" Rysm3 9.8m/S2 0.1 m
=

=
x =




Pgas=87972P0 8 8 uPa
=




the amounto f
we have to calculate pressure from the


the gas
acting
is on
mercury
Pgas Patm-Pe
=




11.10 non-uniform Gwids:
density of an unknown liquid in a manometer



eg egr 2V ?Vs
E->
->
= =




funknown=? mag
->

meg

:"Ira
=

=




ewater-woongim 1,(4) 1000
=


(5)

12 1250kg/m3
=