Announcements

1

• Announcements
• Physics lecture today 4 PM Professor Brian
  Matthews from U. Oregon Tolerance and
  Intolerance in Protein Structure and Function
• Third exam on Chaps. 15-20 Tuesday, Nov. 25th
• Bring
• Equation sheet (8.5? x 11?)
• Calculator
• Clear head
• Extra problem solving session ?
• Sunday night 10-11 PM ?
• Monday evening 6-7 PM ?
• Other ?

2

• Advice for preparing for exam
• Review lecture notes and text chapters
• Prepare equation sheet
• Work problems using equation sheet and calculator
• From homework
• From previous exams
• From on line quizes
• Topics
• Simple harmonic motion resonance
• Wave motion, standing waves, sound waves
• The physics of fluids
• Thermodynamics the ideal gas law

3
Simple harmonic motion resonance
Hookes law

Simple pendulum
4
The notion of resonance Suppose
F-kxF0 sin(Wt) According to Newtons
second law
5
Physics of a driven harmonic oscillator
driving frequency
natural frequency
(mag)
(W2rad/s)
w
6
The phenomenon of wave motion
The wave equation
position time
7
The wave equation Solutions y(x,t) f
(x vt)
function of any shape
Moving pulse Periodic wave
wave vector not spring constant!!!
8
Superposition of waves
Standing wave
9
Constraints of standing waves ( ? 0 )
10
The sound of music String instruments (Guitar,
violin, etc.)
? Couples to sound in the air
11
Sound waves Longitudinal waves propagating in a
fluid or solid
12
Periodic sound wave In terms of pressure
Sound intensity (energy/(unit time unit
area)) Decibel scale
13
Wind instruments (standing waves in air)
14
The Doppler effect
vsound velocity observer moving, source
stationary
observer
source
vS0
d
15

• The physics of fluids.
• Fluids include liquids (usually incompressible)
  and gases (highly compressible).
• Fluids obey Newtons equations of motion, but
  because they move within their containers, the
  application of Newtons laws to fluids introduces
  some new forms.
• Pressure Pforce/area 1 (N/m2) 1
  Pascal
• Density r mass/volume 1 kg/m3 0.001 gm/ml

Note In this chapter P?pressure (NOT MOMENTUM)
16
Density r mass/volume Effects of the
weight of a fluid
P(yDy)
rgDy
y
P(y)
Note In this formulation y is defined to be in
the up direction.
17
For an incompressible fluid (such as mercury)
r 13.585 x 103 kg/m3
(constant)
Example
r 13.595 x 103 kg/m3
18
Buoyant force for fluid acting on a solid
FBrfluidVdisplacedg
FB - mg
0 rfluidVsubmergedg - rsolidVsolidg 0
A
Dy
mg
19
Bouyant forces the tip of the iceburg
Sourcehttp//bb-bird.com/iceburg.html
20
Effects of the weight of a compressible fluid
on pressure.
y-y0(mi)
P (atm)
21
Energetics of fluids
Dx1 v1D t Dx2 v2D t A1 Dx1 A2 Dx2 m r
A1 Dx1
K2 U2 K1 U1 W12 ½ mv22 mgh2 ½ mv12
mgh1 (P1 A1 Dx1 P2 A2 Dx2)
?P2 ½ rv22 rgh2 P1 ½ rv12 rgh1
22
Bernoullis equation P2 ½ rv22 rgh2
P1 ½ rv12 rgh1 Example
Suppose we know A1, A2, r, P, y1, y2
P ½ rv22 rgy2 P0 ½ rv12 rgy1
23
Thermodynamic statement of conservation of energy
First Law of Thermodynamics
DEint Q - W
Work done by system
Heat added to system
Internal energy of system
24
How is temperature related to Eint? Consider an
ideal gas ? Analytic expressions for physical
variables ? Approximates several real
situations Ideal Gas Law P V n R T
temperature (K)
volume (m3)
gas constant (8.31 J/(mole??K))
pressure (Pa)
number of moles
25
Review of results from ideal gas analysis in
terms of the specific heat ratio g º CP/CV