“Drivers’ Ed.” Physics Interesting examples from the Alabama Driver Manual Albert A. Gapud...
-
Upload
dominic-chapman -
Category
Documents
-
view
218 -
download
0
Transcript of “Drivers’ Ed.” Physics Interesting examples from the Alabama Driver Manual Albert A. Gapud...
![Page 1: “Drivers’ Ed.” Physics Interesting examples from the Alabama Driver Manual Albert A. Gapud University of South Alabama gapud@southalabama.edu AAPT-Alabama.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649eb75503460f94bc0b82/html5/thumbnails/1.jpg)
“Drivers’ Ed.” Physics
Interesting examples from the Alabama Driver Manual
Albert A. GapudUniversity of South Alabama
AAPT-Alabama Meeting
Apr 5 2014
![Page 2: “Drivers’ Ed.” Physics Interesting examples from the Alabama Driver Manual Albert A. Gapud University of South Alabama gapud@southalabama.edu AAPT-Alabama.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649eb75503460f94bc0b82/html5/thumbnails/2.jpg)
Issues:
1. Using a seat belt
2. Reducing speed when turning
3. Blind spots
4. Stopping distance
5. Following distance
![Page 3: “Drivers’ Ed.” Physics Interesting examples from the Alabama Driver Manual Albert A. Gapud University of South Alabama gapud@southalabama.edu AAPT-Alabama.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649eb75503460f94bc0b82/html5/thumbnails/3.jpg)
Seat belt• Page 31: Alabama safety belt and child restraint laws
Newton’s Law of Inertia!
Can hurt you…– Consider: If your car hits a wall at 40 mph, you will go
through your windshield at 40 mph.– You keep moving even if the car does not
… unless you make yourself a part of the car.– Also explains why:
• We don’t put things on the dashboard
![Page 4: “Drivers’ Ed.” Physics Interesting examples from the Alabama Driver Manual Albert A. Gapud University of South Alabama gapud@southalabama.edu AAPT-Alabama.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649eb75503460f94bc0b82/html5/thumbnails/4.jpg)
Seat belt• Page 31: Alabama safety belt and child restraint laws
Newton’s Law of Inertia!
Can help you…!– How seat belt locks up!– Clutch lever snaps when belt is jerked– Weighted pendulum tilts when accelerated
![Page 5: “Drivers’ Ed.” Physics Interesting examples from the Alabama Driver Manual Albert A. Gapud University of South Alabama gapud@southalabama.edu AAPT-Alabama.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649eb75503460f94bc0b82/html5/thumbnails/5.jpg)
Reducing speed when turning• Page 22: Reduce speed before making turns.• Centripetal force is required!
– Fc = mv2/R. Reducing v : Required Fc reduced more rapidly.– Usually provided by: static friction.
• Static friction: required for rolling• Coefficient, μs :
– rubber on dry concrete : about 0.8– rubber on wet concrete : about 0.3, less than half!
• Maximum friction = μs N = μs x weight = μs x (1600x 10 N)
• = mv2/R. So max
Example: 90 degree intersection turn: curb radius:
local streets: R = 15 ft = 4.6 m : max v : dry = 6.1 m/s = 14 mph, wet = 3.7 m/s = 8
mph
arterial streets: R = 35 ft = 10.7 m: max v : dry = 9.3 m/s = 21 mph , wet = 5.7 m/s =
13 mph
sm
Rv 16000
![Page 6: “Drivers’ Ed.” Physics Interesting examples from the Alabama Driver Manual Albert A. Gapud University of South Alabama gapud@southalabama.edu AAPT-Alabama.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649eb75503460f94bc0b82/html5/thumbnails/6.jpg)
Mirrors and blind spots• Page 65: Check “blind spot” before changing lanes.• Geometric optics: law of reflection, ray trace
![Page 7: “Drivers’ Ed.” Physics Interesting examples from the Alabama Driver Manual Albert A. Gapud University of South Alabama gapud@southalabama.edu AAPT-Alabama.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649eb75503460f94bc0b82/html5/thumbnails/7.jpg)
Mirrors and blind spots• Page 65: Check “blind spot” before changing lanes.• Geometric optics: law of reflection, ray trace
Blind area on either side due to:
Limited field of view of mirrors
(m.1 and m.2 angled inward)
![Page 8: “Drivers’ Ed.” Physics Interesting examples from the Alabama Driver Manual Albert A. Gapud University of South Alabama gapud@southalabama.edu AAPT-Alabama.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649eb75503460f94bc0b82/html5/thumbnails/8.jpg)
Mirrors and blind spots• Page 65: Check “blind spot” before changing lanes.• Geometric optics: law of reflection, ray trace
Blind area on either side due to:
Limited view of mirrors
(m.1 and m.2 angled outward)
![Page 9: “Drivers’ Ed.” Physics Interesting examples from the Alabama Driver Manual Albert A. Gapud University of South Alabama gapud@southalabama.edu AAPT-Alabama.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649eb75503460f94bc0b82/html5/thumbnails/9.jpg)
Stopping / following distance• Page 38: eye to brain to foot to wheel to road.• Stopping distance: static target (e.g., debris)
– Student exercise? Find reaction time that was used.• tr = 0.74 s
– Student exercise? Find the acceleration (assume constant).• a = -19.4 ft/s2
– Issue with significant digits??
![Page 10: “Drivers’ Ed.” Physics Interesting examples from the Alabama Driver Manual Albert A. Gapud University of South Alabama gapud@southalabama.edu AAPT-Alabama.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649eb75503460f94bc0b82/html5/thumbnails/10.jpg)
Stopping / following distance• Page 37: avoiding rear end collisions
• Comparison: One c.l. per 10 mph vs. 2-sec rules:One c.l. per 10 mph equivalent to: “1.36-sec rule”
2-sec rule equivalent to: “1.47 c.l. per 10 mph”
![Page 11: “Drivers’ Ed.” Physics Interesting examples from the Alabama Driver Manual Albert A. Gapud University of South Alabama gapud@southalabama.edu AAPT-Alabama.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649eb75503460f94bc0b82/html5/thumbnails/11.jpg)
Stopping / following distance• Page 37: avoiding rear end collisions
• How well do these help avoid rear end collisions?Graphed x(t). x1 = x2 means collision.
Other assumptions: same acceleration (deceleration) for the two cars, one shifted by the reaction time.
![Page 12: “Drivers’ Ed.” Physics Interesting examples from the Alabama Driver Manual Albert A. Gapud University of South Alabama gapud@southalabama.edu AAPT-Alabama.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649eb75503460f94bc0b82/html5/thumbnails/12.jpg)
Stopping / following distance• Rules for following distance: comparison
– How do these help, in a typical situation?
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.00
2
4
6
8
10
12
14
16
18
20
22black = your carred = car in front
tr = 0.74 s
1cl/10mph = 1.36 sec
d
ista
nce
, in
ca
r le
ng
ths
time (s)
initial = 55 mphreaction time = 0.74 s
acceleration = 19.6 ft/s2
1 car length = 20 ft
2sec = 1.47 cl/10mph
![Page 13: “Drivers’ Ed.” Physics Interesting examples from the Alabama Driver Manual Albert A. Gapud University of South Alabama gapud@southalabama.edu AAPT-Alabama.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649eb75503460f94bc0b82/html5/thumbnails/13.jpg)
Stopping / following distance• Rules for following distance: comparison
– How do these help, in a typical situation?
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.00
2
4
6
8
10
12
14
16
18
20
22black = your carred = car in front
tr = 0.74 s
+ 2.5 cl
1cl/10mph = 1.36 sec
d
ista
nce
, in
ca
r le
ng
ths
time (s)
initial = 55 mphreaction time = 0.74 s
acceleration = 19.6 ft/s2
1 car length = 20 ft
2sec = 1.47 cl/10mph
+ 5 cl
Separation at stop = d – votr (ft)
or D – (vo/20)tr (cl)
![Page 14: “Drivers’ Ed.” Physics Interesting examples from the Alabama Driver Manual Albert A. Gapud University of South Alabama gapud@southalabama.edu AAPT-Alabama.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649eb75503460f94bc0b82/html5/thumbnails/14.jpg)
Stopping / following distance• Rules for following distance: comparison
– How do these help, in a typical situation?
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.00
2
4
6
8
10
12
14
16
18
20
22black = your carred = car in front
0.54 cl/10mph
tr = 0.74 s
+ 0 cl+ 1 cl+ 2.5 cl
1cl/10mph = 1.36 sec
1sec
d
ista
nce
, in
ca
r le
ng
ths
time (s)
initial = 55 mphreaction time = 0.74 s
acceleration = 19.6 ft/s2
1 car length = 20 ft
2sec = 1.47 cl/10mph
+ 5 cl
Separation at stop = d – votr (ft)
or D – (vo/20)tr (cl)
![Page 15: “Drivers’ Ed.” Physics Interesting examples from the Alabama Driver Manual Albert A. Gapud University of South Alabama gapud@southalabama.edu AAPT-Alabama.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649eb75503460f94bc0b82/html5/thumbnails/15.jpg)
Further Reading: “Car physics”The Isaac Newton School of Driving:
Physics & Your Carby Barry Parker: Professor Emeritus of Physics,
Idaho State University and son of a car mechanic
Mainly a good source of conceptual examples from all fields of physics– Driving, Engines, Electrical system, Brakes,
Suspension & Transmission, Aerodynamics, Collisions
– Racing
– Traffic and Chaos
– Future technologies
(hybrid, fuel cell)
![Page 16: “Drivers’ Ed.” Physics Interesting examples from the Alabama Driver Manual Albert A. Gapud University of South Alabama gapud@southalabama.edu AAPT-Alabama.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649eb75503460f94bc0b82/html5/thumbnails/16.jpg)
Further Reading: “Car physics”Fast Car Physicsby Chuck Edmondson: Professor of Physics, US
Naval Academy, racing enthusiast
More quantitative, detailed treatment, with ultimate goal of fast-car racing: Possible source of student projects?– Finding shift points, shifting properly
– Drag force, gear ratios
– Rounding curves efficiently
– Tires and load transfer
– Steering and suspension
– Future/green technologies
![Page 17: “Drivers’ Ed.” Physics Interesting examples from the Alabama Driver Manual Albert A. Gapud University of South Alabama gapud@southalabama.edu AAPT-Alabama.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649eb75503460f94bc0b82/html5/thumbnails/17.jpg)
Final notes• Many other possible topics• Goal: Show physics in our daily life• Driver’s ed still fresh w/ HS students• “Car physics”: entry point for HS students?
![Page 18: “Drivers’ Ed.” Physics Interesting examples from the Alabama Driver Manual Albert A. Gapud University of South Alabama gapud@southalabama.edu AAPT-Alabama.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649eb75503460f94bc0b82/html5/thumbnails/18.jpg)
Spare slides
![Page 19: “Drivers’ Ed.” Physics Interesting examples from the Alabama Driver Manual Albert A. Gapud University of South Alabama gapud@southalabama.edu AAPT-Alabama.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649eb75503460f94bc0b82/html5/thumbnails/19.jpg)
Stopping / following distance• Rules for following distance: comparison
– How do these help, in a typical situation?
Separation at stop = d – votr (ft)
or D – (vo/20)tr (cl)
Following rule up to t = 0
0 2 4 6 8 10 12 14 16 180
10
20
30
40
50
60
70
80
900.54 cl/10mph 1cl/10mph = 1.36 sec
2sec = 1.47 cl/10mph
black = your carred = car in front
spe
ed
, in
ft/s
distance, in car lengths
initial = 55 mphreaction time = 0.74 s
acceleration = 19.4 ft/s2
1 car length = 20 ft
Here, condition is:
x2 (v=0) > x1 (v=0)