PHY 113 A General Physics I 9-9:50 AM MWF Olin 101 Plan for Lecture 19:
PHY 113 A General Physics I 9-9:50 AM MWF Olin 101 Plan for Lecture 10:
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9/21/2012 PHY 113 A Fall 2012 -- Lecture 10 1 PHY 113 A General Physics I 9-9:50 AM MWF Olin 101 Plan for Lecture 10: Chapter 6 -- Newton’s Laws continued 1.Newton’s Laws and centripetal acceleration 2.Newton’s Laws and resistive forces
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PHY 113 A General Physics I 9-9:50 AM MWF Olin 101 Plan for Lecture 10: Chapter 6 -- Newton’s Laws continued Newton’s Laws and centripetal acceleration Newton’s Laws and resistive forces. iclicker exercise: Exam feedback: Too hard Too easy Neutral. - PowerPoint PPT Presentation
Transcript of PHY 113 A General Physics I 9-9:50 AM MWF Olin 101 Plan for Lecture 10:
PHY 113 A Fall 2012 -- Lecture 10 19/21/2012
PHY 113 A General Physics I9-9:50 AM MWF Olin 101
Plan for Lecture 10:
Chapter 6 -- Newton’s Laws continued
1. Newton’s Laws and centripetal acceleration
2. Newton’s Laws and resistive forces
PHY 113 A Fall 2012 -- Lecture 10 29/21/2012
PHY 113 A Fall 2012 -- Lecture 10 39/21/2012
iclicker exercise:Exam feedback:
A. Too hardB. Too easyC. Neutral
PHY 113 A Fall 2012 -- Lecture 6 49/10/2012
Recall: Uniform circular motion:
animation from http://mathworld.wolfram.com/UniformCircularMotion.html
PHY 113 A Fall 2012 -- Lecture 6 59/10/2012
Uniform circular motion – continued
ra ˆ
:ison accelerati lcentripeta theanddirection radial in the
onaccelerati then the, If
2
rv
vvv
c
fi
PHY 113 A Fall 2012 -- Lecture 6 69/10/2012
Uniform circular motion – continued
r
ra
ra
ra
ˆ2
ˆ2
ˆ
2
2
2
rf
rT
rv
c
c
c
Trv 2
In terms of time period T for one cycle:
In terms of the frequency f of complete cycles:πfrv
Tf 2 ;1
PHY 113 A Fall 2012 -- Lecture 6 79/10/2012
Uniform circular motion and Newton’s second law
r
ra
aF
ˆ2
rv
m
c
iclicker exercise:For uniform circular motion
A. Newton’s laws are repealedB. There is a force pointing radially outward from
the circleC. There is a force pointing radially inward to the
circle
PHY 113 A Fall 2012 -- Lecture 10 89/21/2012
http://earthobservatory.nasa.gov/Features/OrbitsCatalog/page1.php
Example of uniform circular motion:
PHY 113 A Fall 2012 -- Lecture 10 99/21/2012
Example of uniform circular motion: Consider the moon in orbit about the Earth
NaMF
smRT
a
s. days.T
mR
kgM
cM
Mc
M
M
20
232
6
8
22
100.2 Law Second sNewton'
/1072.22
10362327 :Moon of period Rotational
1084.3 :Earth ofcenter from Distance
1035.7 :Moon of Mass
PHY 113 A Fall 2012 -- Lecture 10 109/21/2012
Example of uniform circular motion:
ra ˆ2
rv
c
r̂
sinsin
:law second sNewton' ofcomponent (radial) Horizontal
0cos:law second sNewton' ofcomponent Vertical
22
Lmv
rmvmaT
mgT
c
PHY 113 A Fall 2012 -- Lecture 10 119/21/2012
Example of uniform circular motion:
mgnmgn 0:law second sNewton' ofcomponent Vertical
grμvr
mvmgμnμ
rmvmaf
sss
c
max
2
2
:condition Maximum
:law second sNewton' ofcomponent (radial) Horizontal
PHY 113 A Fall 2012 -- Lecture 10 129/21/2012
Curved road continued:
hrmim/s.smgrμv
mrμ
grμv
s
s
s
/29113 /358.95.0
35 5.0 :Example
max
max
PHY 113 A Fall 2012 -- Lecture 10 139/21/2012
Mass on a swing:
mg
T
iclicker exercise:Which of these statements about the tension T in the rope is true?
A. T is the same for all .B. T is smallest for 0.C. T is largest for 0.
LvmmgT
LvmmgT
2
2
:0For
cos
:rope thealongdirection in the laws sNewton'
L
PHY 113 A Fall 2012 -- Lecture 10 149/21/2012
Newton’s law in accelerating train car
ga
maθTmgT
tan
sin :direction Horizontal0cos :direction Vertical
PHY 113 A Fall 2012 -- Lecture 10 159/21/2012
Models of air friction forces
2
air
:ocitieslarger velFor
:s velocitiesmallFor
DvF
bvF
air
mg
bv
mamgbvv
:0 assuming and asdirection up Denoting
mbteb
mgtv
dtdvmmgbv
S
/1)(
:equation aldifferenti olution to
