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GET LESS WET
By Tilman Guenther,
7
Orefield Middle School
Mrs.Kakaley
Grade:
PROBLEM STATEMENT
If you have to go a certain distance through the
rain, at what speed and body posture will you get
the least wet?
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Run like the wind!
Lean forward and run Become Superman!!
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BACKGROUND INFO
Formulas
What is Rain?
Distance / Time = Speed
[cm]
[sec] [cm/s]
Water density = 1g / cm3
Rain is Condensation of
atmospheric water vapor
that falls under gravity.
Volume = mass / Density
[cm3]
[g]
[g/cm3]
Rain intensity
Drizzle
1 mm/day
Light Rain
2.5 mm/hour
Mod. Rain
10 mm/hour
Heavy Rain
50 mm/hour
Violent Rain
>50 mm/hour
Rain volume [cm3]
------------------------------Area [cm2] x Time [sec]
HYPOTHESIS
If having to go a certain distance through
the rain, then running and slightly leaning
forward will get you the least wet.
VARIABLES
Controlled:
Distance
Independent: Speed
Independent: Posture
Wind is not something
that I added to the
test.
Dependent:
Weight
SETUP EXPLANATION
Overflow
Water uptake
Motor and
Pulling
system
Water Bin
Water pump
MATERIALS
Setup Materials:
Work bench 1.5m
Water basin 1m x 0.2m
Track 1.2m
Rail car for track
Frame to hold basins
Model Human (absorbent)
Twine
Motor & control
Garden hose to refill
Testing Materials:
Rain gauge
Timer
Scale / balance to determine wetness
BUILDING THE RAIN TUNNEL
SETUP
PROCEDURE
4. Weigh Model
1.
Turn on Rain
2. Wait five
minutes
5. Set Variables
6. Run Test
3. Test Rainfall
7. Weigh Model
8. Record Data
Test Rainfall every
5 runs
Run# Posture
[deg]
Speed
[cm/s]
Time Wetness
[sec]
[g]
Wetness vs. Speed (Posture: 0)
1
0
6.24
10.00
12
0
6.50
9.69
6
0
6.55
9.60
2
0
12.80
4.89
8
0
13.00
4.83
13
0
13.00
4.82
9
0
18.70
3.36
3
0
19.50
3.21
14
0
19.80
3.17
15
0
25.50
2.46
10
0
26.20
2.39
4
0
26.50
2.37
16
0
30.90
2.03
11
0
31.00
2.03
5
0
31.50
1.99
9.86
10.01
9.64
5.93
4.86
5.01
3.46
3.66
3.17
2.64
3.30
3.66
2.13
2.80
2.58
• Tested five postures
three times at five
different speeds
• Performed 85 runs total
• Carried out 26
calibration runs
DATA TABLES
Run#
Posture
Speed
Time
Wetness
[deg]
[cm/s]
[sec]
[g]
Wetness vs. Speed (Posture: 0)
1
0
6.24
10.00
9.86
12
0
6.50
9.69
10.01
6
0
6.55
9.60
9.64
2
0
12.80
4.89
5.93
8
0
13.00
4.83
4.86
13
0
13.00
4.82
5.01
9
0
18.70
3.36
3.46
3
0
19.50
3.21
3.66
14
0
19.80
3.17
3.17
15
0
25.50
2.46
2.64
10
0
26.20
2.39
3.30
4
0
26.50
2.37
3.66
16
0
30.90
2.03
2.13
11
0
31.00
2.03
2.80
5
0
31.50
1.99
2.58
7
0
32
-45
6.05
10.40
20.93
27
-45
6.18
10.10
18.99
49
-45
6.31
9.97
19.89
50
-45
12.20
5.12
11.60
28
-45
12.50
5.04
15.98
33
-45
12.80
5.10
13.11
51
-45
18.50
3.39
8.49
29
-45
18.80
3.34
9.83
34
-45
19.70
3.18
7.75
52
-45
25.50
2.50
6.47
35
-45
25.70
2.45
6.07
36
-45
26.30
2.38
6.19
30
-45
26.50
2.37
5.99
31
-45
29.80
2.11
4.89
53
-45
31.40
2.00
5.96
Wetness vs. Speed (Posture: -45)
Wetness vs. Speed (Posture: -22)
70
-22
5.93
10.60
15.99
42
-22
6.16
10.20
14.64
65
-22
6.17
10.20
16.61
43
-22
12.20
5.13
8.06
66
-22
12.20
5.15
9.45
71
-22
13.00
4.84
9.21
67
-22
18.50
3.40
7.09
72
-22
19.30
3.26
5.92
83
-22
19.80
3.16
5.97
68
-22
25.30
2.48
5.00
84
-22
25.80
2.43
5.11
73
-22
25.80
2.44
4.76
85
-22
27.90
2.25
4.69
74
-22
30.40
2.07
4.64
69
-22
30.70
2.05
4.49
Wetness vs. Speed (Posture: 22)
37
22
6.32
9.95
17.29
60
22
6.35
9.91
17.73
54
22
6.52
9.66
16.77
38
22
12.70
4.93
9.11
61
22
13.00
4.84
7.19
55
22
13.10
4.00
9.70
62
22
19.40
3.32
5.06
56
22
19.80
3.17
6.22
39
22
20.30
3.09
5.50
63
22
25.90
2.42
3.67
57
22
26.60
2.36
3.72
40
22
27.20
2.29
3.62
41
22
28.70
2.19
2.72
59
22
30.70
2.04
3.49
64
22
31.00
2.00
3.41
Wetness vs. Speed (Posture: 45)
44
45
6.11
10.30
25.11
22
45
6.33
9.94
22.40
17
45
6.53
9.64
20.86
23
45
12.40
5.07
11.98
45
45
12.40
5.07
11.51
18
45
13.10
4.79
9.73
46
45
18.50
3.39
7.55
24
45
19.30
3.25
7.50
19
45
19.70
3.18
6.22
47
45
25.50
2.47
5.28
25
45
26.20
2.39
5.11
20
45
26.90
2.34
4.61
21
45
31.10
2.02
4.08
26
45
31.10
2.09
4.04
48
45
32.40
1.94
4.19
75
0
147.00
0.42
1.78
76
0
174.00
0.36
1.77
77
0
98.70
0.63
1.64
78
0
116.00
0.54
1.54
79
0
53.50
1.17
2.06
80
0
100.00
0.63
2.19
81
0
58.30
1.00
2.40
82
0
112.00
0.56
1.88
58
RAINFALL CALIBRATION
Calibration Runs
120
Volume
85.034 gram
Surface area 34.6 cm2
60 sec
Rainfall Amount [g]
100
80
60
40
20
0
1
3
5
7
9
11 13 15 17 19 21 23 25
Run #
Pre-Calibrations
Calibrations between tests
Rain intensity
WETNESS COMPARED TO SPEED
(CONSTANT POSTURE)
Wetness versus Speed
12
Wetness [g]
10
8
6
4
2
0
0
50
100
Speed [cm/s]
150
WETNESS COMPARED TO SPEED
OBSERVATIONS
(CONSTANT POSTURE)
Observations:
1. The faster you go the
less wet you get
2. This is true until a
certain point; if you go
any faster, you will still
get wet equally
Wetness versus Speed
12
10
8
6
4
2
0
0
50
100
150
WETNESS COMPARED TO POSTURE
(CONSTANT SPEED)
Wetness vs. Posture
12
Wetness [g]
10
8
6
4
2
0
-45
-30
-15
0
Posture [deg]
15
30
45
WETNESS COMPARED TO POSTURE
(CONSTANT SPEED)
2. If you need to lean,
lean forward
12
10
Wetness [g]
Observations:
1. When you don’t lean,
you will get the least
wet
Wetness vs. Posture
8
6
4
2
0
-45
-30
-15
0
15
Posture [deg]
30
45
ANALYSIS
Top Wetness
Variables:
1. Top Surface area
------ Constant
2. Time & Speed of run ------ Variable (distance constant)
3. Rainfall Intensity
------ Constant
The longer you stay in the rain, the wetter
you will get from the top
Wetness
Speed (= 1 / time)
ANALYSIS
Front Wetness
Variables:
1. Distance
2. Front surface area
3. Rainfall Density
------ Constant
------ Variable
------ Constant
As long as you do not stand still, distance
is connected directly with wetness
Wetness
Speed
ANALYSIS CONCLUSION
Wetness
Wetness
Speed
Look familiar??
Speed
Wetness versus Speed
12
10
Wetness
8
6
4
2
0
Speed
0
50
100
150
ANALYSIS CONCLUSION
My Java simulation rain
calculator application
CONCLUSION
The purpose of my experiment was to
discover what speed and posture will get you the
least wet when running though the rain. My
original hypothesis was that running and slightly
leaning forward is the option to get the least wet
but I was wrong, fast speed is good, but leaning
causes more wetness. The only error that
occurred was when the holes where the rain came
out were clogged but I realized this in time and
no harm was done. If I did this again I would test
additional variables such as wind speed and
direction, rain droplet size, and rain intensity.
BIBLIOGRAPHY
Background
Water
"Why raindrops are different sizes." USGS. USGS, 8 Feb. 2011. Web. 23
Oct. 2011.
http://ga.water.usgs.gov/edu/raindropsizes.html
Physic book (hypertextbook.co,)
Building the rain tunnel
No refs found!
Lots of experimentation
Similar experiments (not as good Thorough
Savage, Adam, and Jamie Hyneman. Mythbusters: Running in the Rain
MiniMyth. Discovery Channel, 2003.
Discovery videos. Web. 24 Oct. 2011. <http://dsc.discovery.com/videos/
mythbusters-running-in-the-rain-minimyth.html>.