PHY 113 A Fall 2012 -- Lecture 36 112/05/2012
PHY 113 A General Physics I9-9:50 AM MWF Olin 101
Plan for Lecture 36:Review – Part I
1. General advice about how to study2. Some comments on sound and waves3. Review of past exam questions
Review – Part II (Friday)4. Systematic review of PHY 113 topics
PHY 113 A Fall 2012 -- Lecture 36 212/05/2012
PHY 113 A Fall 2012 -- Lecture 36 312/05/2012
Comments on final exam for PHY 113
Date: Thursday, Dec. 13, 2012 at 9 AMPlace: Olin 101Format: Similar to previous exams; covering material in Lectures 1-37, Chapters 1-22 (no time pressure)Focus: Basic physics concepts; problem-solving techniquesBring:
1. Clear head2. Calculator3. Pencils, pens4. Up to 4 equation sheets
PHY 113 A Fall 2012 -- Lecture 36 412/05/2012
iclicker question:What is the purpose of the final exam in PHY 113
A. No purpose – just pain and sufferingB. To improve my grade in the courseC. It is a college tradition that must be
maintainedD. To check that I have actually learned the
materialE. To encourage students to review the course
material and solidify my learning
PHY 113 A Fall 2012 -- Lecture 36 512/05/2012
Comments on waves and sound1. Standing wave resonances for strings or
pipes2. Relationship between wave speed,
frequency, and wavelength3. Doppler effect
PHY 113 A Fall 2012 -- Lecture 36 612/05/2012
ctxytxyctxytxy leftright λ
π2sin),( λπ2sin),( 00
ftxytxtxy leftright π2cosλπ2sin2),(y),( 0
“Standing” wave: (lf=c)
Formation of standing waves; beautiful trigonometric identity: BABABA 2
12
1 cossin2sinsin
PHY 113 A Fall 2012 -- Lecture 36 712/05/2012
.....4,3,2,1 22
sin0
: wavestring ersefor transv shapes spatial Possible
nπxLnA)y(x,
...........4,3,2,1 2
2
2cos2sin :form waveStanding
nLncf
nL
πftλπxAy(x,t)
nnl
PHY 113 A Fall 2012 -- Lecture 36 812/05/2012
Musical scale (chromatic)
harmonic) 2( Hz 880 tension)adjusting(by m/s 440set must string, m 0.5 aon Hz 440 :Afor :Example
...........4,3,2,1 2
:string aon wavesstandingFor
2
1
nfcf
nLncfn
PHY 113 A Fall 2012 -- Lecture 36 912/05/2012
Standing waves in air c=343 m/s:
Hz 660 Hz 220 :A
m 39.0For
...........5,3,1 4
: wavesstanding closed-openFor
Hz 880 Hz 440 :A
m 39.0For
...........4,3,2,1 2
: wavesstandingopen -openFor
3
1
2
1
ffL
nLncf
ffL
nLncf
n
n
PHY 113 A Fall 2012 -- Lecture 36 1012/05/2012
The “Doppler” effect v=sound velocity
observer stationary, source moving
vvvT
ftt
dTvTtvdvt
S
O
S
112
2
1
d
SSO vvvff
toward
awayS
OSO vv
vvff
:Summary
PHY 113 A Fall 2012 -- Lecture 36 1112/05/2012
S
OSO vv
vvff
:effectDoppler sound ofSummary toward
away
R
RSO vv
vvff
: wavesneticelectromagfor effect Doppler
Relative velocity of source toward observer
Hz 104.4 Hz103/301103/301440 m/s103radar For
Hz 482 Hz )343/301/(440 m/s343 soundFor m/s30 and 0 suppose and Hz 440 :Example
5-8
88
SO
O
ROSS
ffv
fvvvvf
PHY 113 A Fall 2012 -- Lecture 36 1212/05/2012
iclicker question:The previous calculation for “radar” Doppler was:
A. Encouraging me to speed because it is impossible to detect such a small frequency difference
B. Full of admiration that Doppler radar equipment can detect such a small frequency difference
C. Not relevant to actual “radar” Doppler -- still need to be careful not to speed
iclicker question:The fallacy in the previous analysis was
A. Incorrect value of fs
B. Incorrect value of v (speed of light)C. Calculator error
PHY 113 A Fall 2012 -- Lecture 36 1312/05/2012
R
RSO vv
vvff
: wavesneticelectromagfor effect Doppler
Relative velocity of source toward observer
Hz 102 Hz103/301103/3011020 m/s103radar For
m/s30 suppose Hz; 1020 :sfrequencieradar Typical
38
898
9
SO
RS
ffv
vf
PHY 113 A Fall 2012 -- Lecture 36 1412/05/2012
PHY 113 A Fall 2012 -- Lecture 36 1512/05/2012
PHY 113 A Fall 2012 -- Lecture 36 1612/05/2012
Review questions from Exam 4:
PHY 113 A Fall 2012 -- Lecture 36 1712/05/2012
Review questions from Exam 4:
PHY 113 A Fall 2012 -- Lecture 36 1812/05/2012
Review questions from Exam 4:
PHY 113 A Fall 2012 -- Lecture 36 1912/05/2012
Review questions from Exam 4:
PHY 113 A Fall 2012 -- Lecture 36 2012/05/2012
Review questions from Exam 3:
PHY 113 A Fall 2012 -- Lecture 36 2112/05/2012
Review questions from Exam 3:
PHY 113 A Fall 2012 -- Lecture 36 2212/05/2012
Review questions from Exam 2:
PHY 113 A Fall 2012 -- Lecture 36 2312/05/2012
Review questions from Exam 2:
PHY 113 A Fall 2012 -- Lecture 36 2412/05/2012
Review questions from Exam 2: