VISUAL PHYSICS School of Physics University of Sydney Australia
-
Upload
kiona-estes -
Category
Documents
-
view
16 -
download
0
description
Transcript of VISUAL PHYSICS School of Physics University of Sydney Australia
![Page 1: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/1.jpg)
VISUAL PHYSICSSchool of PhysicsUniversity of SydneyAustralia
![Page 2: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/2.jpg)
goldm1 V1
goldm2 V2
m V
gold = m1 / V1 = m2 / V2
m = V V = m /
![Page 3: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/3.jpg)
pressure !!!
![Page 4: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/4.jpg)
A
F
![Page 5: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/5.jpg)
![Page 6: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/6.jpg)
Gauge and absolute pressures
Pressure gauges measure the pressure above and below atmospheric (or barometric) pressure.
Patm = P0 = 1 atm = 101.3 kPa = 1013 hPa = 1013 millibars = 760 torr = 760 mmHg
Gauge pressure Pg
Absolute pressure P
P = Pg + Patm
0
100
200
300
400
![Page 7: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/7.jpg)
![Page 8: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/8.jpg)
0
100
200
300
400
![Page 9: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/9.jpg)
Impact of a molecule on the wall of the container exerts a force on the wall and the wall exerts a force on the molecule. Many impacts occur each second and the total average force per unit area is called the pressure.
![Page 10: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/10.jpg)
![Page 11: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/11.jpg)
The pressure in a fluid can be defined as the ratio of the force exerted by the fluid to the area over which it is exerted. To get the pressure at a point you need to take the limit as this area approaches zero. Because of the weak cohesive forces between the molecules of the fluid, the only force that can be applied by the fluid on a submerged object is one that tends to compress it. This means the force of the fluid acts perpendicular to the surface of the object at any point.
![Page 12: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/12.jpg)
p0 pressure acting at on surface
h
Liquid – uniform density
A
Weight of column of liquid F
![Page 13: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/13.jpg)
(0,0)h
ph
p0
(0,0)h
ph
p0
p0’
Linear relationship between pressure and depth.If the pressure at the surface increases then the pressure at a depth h also increases by the same amount.
![Page 14: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/14.jpg)
![Page 15: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/15.jpg)
h
The pressure exerted by a static fluid depends only upon the depth of the fluid, the density of the fluid, and the acceleration of gravity
ph = p0 + g h
Static pressure does not depend upon mass or surface area of liquid and the shape of container due to pressure exerted by walls.
![Page 16: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/16.jpg)
Cloudy / rainsunshine
![Page 17: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/17.jpg)
![Page 18: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/18.jpg)
?
![Page 19: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/19.jpg)
A
D
CB
h
![Page 20: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/20.jpg)
hpatm
patm
B
A
C
![Page 21: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/21.jpg)
h2
h1
F1F2
A1 A2
oil
![Page 22: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/22.jpg)
A sharp blow to the front of an eyeball will produce a higher pressure which is transmitted to the opposite side
![Page 23: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/23.jpg)
Another example is the pressure exerted by a growing tumour. This increased pressure is transmitted down the spinal column via the cerebrospinal fluid, and may be detected lower in the spinal cavity which is less invasive than trying to detect it in the brain itself.
tumor
Increased pressure transmitted down spinal cord
![Page 24: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/24.jpg)
![Page 25: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/25.jpg)
Partially submerged floating
![Page 26: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/26.jpg)
Floating: partially submerged
Weight of object < weight of fluid that can be displaced by object
Volume of displaced water < volume of object
Weight of liquid displaced by partially submerged object = weight of object
Water displaced
![Page 27: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/27.jpg)
Floating: fully submerged
Weight of object = weight of fluid displaced by object
Volume of displaced water = volume of object
Water displaced
Static equilibrium
Some fish can remain at a fixed depth without moving by storing gas in their bladder.
Submarines take on or discharge water into their ballast tanks to rise or dive
![Page 28: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/28.jpg)
Sinks
Weight of object > weight of fluid displaced by object
Volume of displaced water = volume of object
Water displaced
![Page 29: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/29.jpg)
A steel ship can encompass a great deal of empty space and so have a large volume and a relatively small density.
Volume of water displaced
Weight of ship = weight of water displaced
![Page 30: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/30.jpg)
Volume of water displaced. This volume is not necessarily the volume present.
Weight of ship = weight of water displaced
The buoyant force is equal to the weight of the water displaced, not the water actually present. The missing water that would have filled the volume of the ship below the waterline is the displaced fluid.
![Page 31: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/31.jpg)
h
F
topbottom
Object partially submerged
A
o
h
F
topbottom
Object fully submerged
A
ow
FLOATING: weight of object = buoyant force
FB
FG
+
![Page 32: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/32.jpg)
![Page 33: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/33.jpg)
?water
oil
![Page 34: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/34.jpg)
Flift + FB
FG
a = 0m
Flift + FB = FG
![Page 35: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/35.jpg)
Cohesion: attractive forces between “like” molecules
F = 0F
Net force on molecule at surface is into bulk of the liquid
FT
Surface of any liquid behaves as though it is covered by a stretched membrane
![Page 36: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/36.jpg)
pull up on surface push down on surface
restoring forces
![Page 37: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/37.jpg)
Which shape corresponds to a soap bubble?
Surface of a liquid acts like an elastic skin minimum surface potential energy minimum
surface area for given volume
![Page 38: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/38.jpg)
FLOATING NEEDLENot a buoyancy phenomena
FG
FT
Surface tension acts along length of needle on both sides
Length of needle, L
Equilibrium FT = FG
FT = 2 T L
Coefficient ofsurface tension T
![Page 39: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/39.jpg)
k = 0.70 N.m-1
x = 3410-3 m
radius of ringR = 2010-3 m
mass of ring m = 7.0 10-4 kg
Fspring = Fe = k x
FT + FG
ring
![Page 40: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/40.jpg)
FLOATING NEEDLENot a buoyancy phenomena
FG
FT
Surface tension acts along length of needle on both sides
Length of needle, L
Equilibrium FT = FG
FT = 2 T L
Coefficient ofsurface tension, T
![Page 41: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/41.jpg)
Why can an insect walk on water?
FT = T L = 2 R TFG
FT
Surface tension force actsaround the surface of the leg
For one leg
FG = mg / 6
FT cos
![Page 42: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/42.jpg)
![Page 43: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/43.jpg)
stationary wall
L
Flow of a viscous fluid
low speed
high speed
plate moving with speed v
X
Z
linear velocity gradient
vz = (d / L) v
vz = (v / L) d
d
vz = 0
vz = v
![Page 44: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/44.jpg)
Flow of a viscous newtonain fluid through a pipeVelocity Profile
Adhesive forces between fluid and surface fluid stationary at surface
Parabolic velocity profile
Cohesive forces between molecules layers of fluid slide past each other generating frictional forces energy dissipated (like rubbing hands together)
![Page 45: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/45.jpg)
Poiseuille’s Law: laminar flow of a newtonian fluid through a pipe
volume flow rate Q = dV/dt
Q = dV/dt
R
L
p1 p2
p = p1 - p2
Q = dV = p R4
8 Ldt
parabolic velocity profile
p1 > p2 pressure drop along pipe energy
dissipated (thermal) by friction between
streamlines moving past each other
![Page 46: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/46.jpg)
Velocity of particle - tangent to streamline
streamlines
Streamlines for fluid passing an obstacle
v
![Page 47: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/47.jpg)
Velocity profile for the laminar flow of a non viscous liquid
![Page 48: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/48.jpg)
A1
A2
v1
v2
![Page 49: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/49.jpg)
A1
A2
v1
v2
A1
v1
Low speedLow KEHigh pressure
high speedhigh KElow pressure
Low speedLow KEHigh pressure
![Page 50: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/50.jpg)
y1
y2
x1
x2 p2
A2
A1v1
v2
p1
X
Y
time 1
time 2
m
m
![Page 51: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/51.jpg)
high speedlow pressure
force
force
![Page 52: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/52.jpg)
velocity increasedpressure decreased
low pressurehigh
pressure(patm)
high velocity flow
![Page 53: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/53.jpg)
1
5
Same speed and pressure across river
faster flow (streamlines closer together) low pressure
slow flow(streamlines further apart) high pressure
![Page 54: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/54.jpg)
v small v smallv large
p large p large
p small
![Page 55: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/55.jpg)
artery
External forces causes artery to collapse
Flow speeds up at constrictionPressure is lowerInternal force acting on artery wall is reduced
![Page 56: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/56.jpg)
(1) Point on surface of liquid
(2) Point just outside hole
v2 = ? m.s-1
y1
y2
![Page 57: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/57.jpg)
(1)
(2)
F
m
h
v1 = ?
![Page 58: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/58.jpg)
C
B
A
D
yA
yB
yC
![Page 59: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/59.jpg)
Ideal fluid
Real fluid
![Page 60: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/60.jpg)
![Page 61: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/61.jpg)
![Page 62: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/62.jpg)
![Page 63: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/63.jpg)
![Page 64: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/64.jpg)
leg
lung
leg
lung
armhead
heart
arm
trunk
![Page 65: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/65.jpg)
![Page 66: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/66.jpg)
Floating ball
![Page 67: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/67.jpg)
Lift FL
drag FD
Resultant FR
C
D
BA
![Page 68: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/68.jpg)
low pressure region
high pressure region
rotational KE of eddies heating effect increase in internal energy temperature increases
Drag force dueto pressure difference
motion of air
motion of object
![Page 69: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/69.jpg)
low pressure region
high pressure region
rotational KE of eddies heating effect increase in internal energy temperature increases
Drag force dueto pressure difference
NO CURVEDrag force is opposte to the direction of motion
![Page 70: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/70.jpg)
Tear drop shape for streamlining
![Page 71: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/71.jpg)
t t
vTvT
v v
Object falling from rest Object thrown down with initial speed v0 > vT
![Page 72: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/72.jpg)
![Page 73: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/73.jpg)
low pressure region
high pressure region
Drag force dueto pressure difference
v
v
flow speed (high) vair + v reduced pressure
flow speed (low) vair - v increased pressure
vair (vball)
Boundary layer – air sticks to ball (viscosity) – air dragged around with ball
MAGNUS EFFECT
![Page 74: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/74.jpg)
Golf ball with backspin (rotating CW) with air stream going from left to right. Note that the air stream is deflected downward with a downward force. The reaction force on the ball is upward. This gives the longer hang time and hence distance carried.
The trajectory of a golf ball is not parabolic
![Page 75: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/75.jpg)
![Page 76: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/76.jpg)
lift
![Page 77: VISUAL PHYSICS School of Physics University of Sydney Australia](https://reader033.fdocuments.in/reader033/viewer/2022051416/568134e5550346895d9c1ae9/html5/thumbnails/77.jpg)
Direction plane is moving w.r.t. the air
Direction air is moving w.r.t. plane
low pressure drag
attack angle
lift
downwashhuge vortices
momentum transfer
low pressure
high pressure