Transcript Introduction to Modern Physics PHYX 2710

Physics of Technology
PHYS 1800
Lecture 19
Introduction
Section 0
Fluids
Lecture 1
Slide 1
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Fluids
Lecture 19 Slide 1
PHYSICS OF TOF
ECHNOLOGY
- PHYS 1800
PHYSICS
TECHNOLOGY
ASSIGNMENT SHEET
Spring 2009Spring
Assignment
Sheet
2009
Date
Day
Lecture
Feb 16
M
Presidents Day
17
Tu
Angular Momentum (Virtual Monday)
18
W
Review
19
H
Test 2
20
F*
Static Fluids, Pressure
Feb 23
M
Flotation
25
W
Fluids in Motion
27
F*
Temperature and Heat
Mar 2
M
First Law of Thermodynamics
4
W
Heat flow and Greenhouse Effect
6
F*
Climate Change
Mar 9-13
M-F
Spring Break
Mar 16
M
Heat Engines
18
W
Power and Refrigeration
20
F*
Electric Charge
Mar 23
M
Electric Fields and Electric Potential
25
W
Review
26
H
Test 3
27
F*
Electric Circuits
Mar 30
M
Magnetic Force Review
Apr 1
W
Electromagnets
3
F
Motors and Generators
Apr 6
M
Making Waves
8
W
Sound Waves
10
F*
E-M Waves, Light and Color
Apr 13
M
Mirrors and Reflections
Introduction
Section
0 Lecture 1 Slide 2
15
W
Refraction and Lenses
17
F*
Telescopes and Microscopes
Apr 20
M
Review
22
W
Seeing Atoms
24
F
The really BIG & the really small
INTRODUCTION TO Modern Physics PHYX 2710
May
1
F
Final Exam: 09:30-11:20am
Chapter
No Class
8
5-8
5-8
9
9
9
10
10
10
No Classes
11
11
12
12
13
9-12
13
14
9-12
14
15
15
16
17
17
17
1-17
18 (not on test)
21 (not on test)
Homework Due
-
6
7
8
-
9
10
11
No test week
12
Fall 2004
* = Homework Handout
*Homework Handout
Physics of Technology—PHYS 1800
Spring 2009
Fluids
Lecture 19 Slide 2
Physics of Technology
PHYS 1800
Lecture 19
Fluids and Thermodynamics
Introduction
Section 0
Lecture 1
Slide 3
An Aside Into Atoms
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Fluids
Lecture 19 Slide 3
Describing Motion and Interactions
Position—where you are in space (L or meter)
Velocity—how fast position is changing with time (LT-1 or m/s)
Acceleration—how fast velocity is changing with time (LT-2 or m/s2)
Force— what is required to change to motion of a body (MLT-2 or kg-m/s2 or N)
Inertia (mass)— a measure of the force needed to change the motion of a body (M)
Energy—the potential for an object to do work. (ML2T-2 or kg m2/s2 or N-m or J)
Work is equal to the force applied times the distance moved. W = F d
Kinetic Energy is the energy associated with an object’s motion. KE=½ mv2
Potential Energy is the energy associated with an objects position.
Gravitational potential energy PEgravity=mgh
Spring potential energy PEapring= -kx
Lecture
1 Slide
4 in another object (MLT-1 or kg-m/s)
Momentum—Introduction
the potentialSection
of an 0object
to induce
motion
Angular Momentum and Rotational Energy— the equivalent constants of motion for rotation (MT-1 or
kg/s) and (MLT-2 or kg m/s2 or N)
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Fluids
Lecture 19 Slide 4
A MUCH Closer Look at Collisions
Look
here
carefully!
Introduction
Section 0
Lecture 1
Slide 5
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Fluids
Lecture 19 Slide 5
Compression on an Atomic Scale
Bonds between atoms in a compressed solid can be treated as
compressed springs.
+
+
+
+
Ultimately the forces come from electrostatic interactions
between electrons and protons (and a little quantum mechanics).
+
+
Section 0
Lecture 1
Slide 6
+
+
Introduction
Fspring=-k Δx
+
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Fluids
Lecture 19 Slide 6
Matter is made up of atoms…
• The Atomic Theory, a cornerstone
of modern science, was proposed
by an early Greek thinker,
Democritus (c.460 BC - c.370
BC).
• 2400 year later, Feynman
deemed this the most important
notion in science
Introduction
Section 0
Lecture 1
Slide 7
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Fluids
Lecture 19 Slide 7
So begins the quest to see atoms…
• What is an atom?
• What do atoms look like?
• How do atoms move?
• How big is an atom?
Introduction
Section 0
8
• Slide
How
can you see atoms?
Lecture 1
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Fluids
Lecture 19 Slide 8
The case for the existence of atoms…
• Strong opposition to atomic theory:
(1860s) Lord Kelvin
• The Periodic Table: (1871) Mendeleyev
• Statistical Mechanics: (1890s)
Boltzmann
• X-Rays: (1895) Röntgen
• Quantum Theory: (1913) Bohr and
Einstein
Introduction
Section 0
Lecture 1
Slide 9
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Fluids
Lecture 19 Slide 9
By listing the elements in order of increasing atomic mass, Mendeleev
organized the elements into a table with elements of similar properties
aligned into columns. This is called the periodic table.
Introduction
Section 0
Lecture 1
Slide 10
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Fluids
Lecture 19 Slide 10
Trying to see atoms…
Optical image
STM Image
(5 X mag)
(3,000,000 X
mag)
SEM Image
STM Image
(300,000 X
mag)
(24,000,000
mag)
Introduction
Section 0
Lecture 1
Slide 11
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Magnified images of semiconductor chip.
Physics of Technology—PHYS 1800
Spring 2009
Fluids
Lecture 19 Slide 11
Examples of STM images…
• Pt (100)
with
vaccancies
• Si (111) 7x7
reconstructi
on
Introduction
Section 0
• Annealed
Lecture 1 Slide 12
decanethiol
film on
Au(111)
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Fluids
• Si (111) with
Lecture 19 Slide 12
Applications of knowledge on the atomic scale…
• Feynman: “Plenty
of room at the
bottom”
– Inevitability of small
– Interface of
quantum mechanics
with applications
Introduction
Section 0
Lecture 1
Slide 13
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Fluids
Lecture 19 Slide 13
Engineering Nanomachines
Introduction
Section 0
Lecture 1
Slide 15
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Fluids
Lecture 19 Slide 15
Designer Molecules
Introduction
Section 0
Lecture 1
Slide 16
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Fluids
Lecture 19 Slide 16
Introduction
Section 0
Lecture 1
Slide 17
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Fluids
Lecture 19 Slide 17
States of Matter
Introduction
Section 0
Lecture 1
Slide 18
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Fluids
Lecture 19 Slide 18
States of Matter
Introduction
Section 0
Lecture 1
Slide 19
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Fluids
Lecture 19 Slide 19
Understanding the
behavior of fluids
and
UNIT TWO
thermodynamics
is
Fluids
and Heat
crucial to
understanding
engines and energy
utilization.
Introduction
Section 0
Lecture 1
Slide 20
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Fluids
Lecture 19 Slide 20
UNIT TWO
Fluids and Heat
Introduction
Section 0
Lecture 1
Slide 21
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Fluids
Lecture 19 Slide 21
Physics of Technology
PHYS 1800
Lecture 19
Fluids
Introduction
Section 0
Lecture 1
Slide 22
Introduction
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Fluids
Lecture 19 Slide 22
Pressure
explains...
Introduction objects
Section 0 Lecture 1
floating
and moving fluids
Slide 23
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Fluids
Lecture 19 Slide 23
Dennison’s Laws of Fluids
• When push comes to shove, fluids are just like
other stuff.
• Pascal’s Principle: Pressure extends uniformly in all
directions in a fluid.
• Boyle’s Law: Work on a fluid equals PΔV
• Bernoulli’s Principle: Conservation of energy for fluids
Introduction
Section 0
Lecture 1
Slide 24
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Fluids
Lecture 19 Slide 24
Physics of Technology
PHYS 1800
Lecture 19
Fluids
Introduction
Pascal’s
Lecture 1 SlidePrinciple:
25
Pressure extends uniformly in
all directions in a fluid.
Section 0
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Fluids
Lecture 19 Slide 25
Pressure and Pascal’s Principle
Why does a small woman
wearing high-heel shoes
sink into soft ground more
than a large man wearing
large shoes?
Introduction
Section 0
Lecture 1
Slide 26
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Fluids
Lecture 19 Slide 26
Pressure
• The man weighs more, so he exerts
a larger force on the ground.
• The woman weighs less, but the
force she exerts on the ground is
spread over a much smaller area.
• Pressure takes into account both
force and the area over which the
force is applied.
– Pressure is the ratio of the force to
the area over which it is applied:
– Units: 1 N/m2 = 1 Pa (pascal)
– Pressure is the quantity that
determines whether the soil will
yield.
Introduction Section 0 Lecture 1 Slide
INTRODUCTION TO Modern Physics PHYX 2710
F
P
A
27
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Fluids
Lecture 19 Slide 27
Pressure and Force
• Fluids don’t support unconfined
forces
• So consider a piston in a
confined cylinder
• Force is spread over the full area
of the piston
• We call this pressure, P=F/A
(ML-1T-2 or kg/m-s2 or N/m2 or Pa)
• Work is ΔW=F Δd
or in
the case
of0 fluids
Introduction
Section
Lecture 1
ΔW = (P A) Δd = P ΔV
Slide 28
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Fluids
Lecture 19 Slide 28
Pascal’s Principle
• What happens inside a
fluid when pressure is
exerted on it?
• Does pressure have a
direction?
• Does it transmit a force
to the walls or bottom of
a container?
Introduction
Section 0
Lecture 1
Slide 29
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Fluids
Lecture 19 Slide 29
Pascal’s Principle
• Fluid pushes outward uniformly in all
directions when compressed.
• Any increase in pressure is transmitted
uniformly throughout the fluid.
• Pressure exerted on a piston extends
uniformly throughout the fluid, causing
it to push outward with equal force per
unit area on the walls and the bottom of
the cylinder.
• This is the basis of Pascal’s Principle:
– Any change in the pressure of a
fluid is transmitted uniformly in all
directions
throughout
fluid.
Introduction Section
0 Lecture 1the
Slide
30
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Fluids
Lecture 19 Slide 30
•
•
•
•
•
•
•
Gas molecules lack strong interactions.
Pressure is understood as resulting from
momentum transfer to the container walls
through unbalanced collisions
Pressing on one surface adds force and
hence imparts impulse to the gas
That impulse is taken up as added collisons
(pressure) on other surfaces
The random nature of the motion of gas
particles assures that the force is distributed
evenly to all surfaces
For fixed walls, a decrease in V results in an
increase in P
For expandable walls (like a balloon) the
volume “appears elsewhere to make up for
the lost volume
Introduction
Section 0
Lecture 1
Pascal’s Principle for
Gases
Slide 31
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Fluids
Lecture 19 Slide 31
•
•
•
•
+
Section 0 + Lecture 1
+
+
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
+
Physics of Technology—PHYS 1800
Spring 2009
Pascal’s Principle
for Liquids
+ + + + + +
+ + + + + +
Introduction
+
+ + + + + +
•
Liquid molecules have strong interactions.
Liquids do not compress much
Pressure is understood as resulting from
momentum transfer to the container walls
through unbalanced spring forces
Pressing on one surface adds force that is
transferred to other springs
The network nature of the forces on the particles
assures that the force is distributed evenly to all
surfaces
For expandable walls (like a balloon) the volume
“appears elsewhere to make up for the lost
volume
For fixed walls, a small decrease in V (a
compression) results in a large increase in P
For solids, you can think of the strong forces
holding the atoms in there equilibrium positions,
equivalent to fixed walls
+ + + + + +
•
•
•
+
+
Slide
+ 32
+
+
+
Fluids
Lecture 19 Slide 32
Physics of Technology
Next Lab/Demo:
Rotational Motion
Fluids
Thursday 1:30-2:45
ESLC 46
Ch 8 and 9
Next Class:
Monday 10:30-11:20
BUS
Slide 33318 room
Read Ch 9
Introduction
Section 0
Lecture 1
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Fluids
Lecture 19 Slide 33