SAIL AWAY
MOTION AND FORCES
Institute Of Electrical And Electronics Engineers, Phoenix Section
Teacher In Service Program / Engineers In The Classroom (TISP/EIC)
“Helping Students Transfer What Is Learned In The Classroom To The World Beyond”
SEPTEMBER 2011
AZ Science Lab
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Copyright Notice
This presentation includes material copied from these web sites:
KQED – Quest, Physics Of Sailing,
http://www.kqed.org/quest/television/the-physics-of-sailing
The Internet Encyclopedia Of Science – Archimedes’ Principle,
http://www.daviddarling.info/encyclopedia/A/Archimedes_principle.html
Pitara Kids Network - Scientists Find More on the Eureka Man,
http://www.pitara.com/discover/eureka/online.asp?story=107
Forces & Moments, http://www.univie.ac.at/cga/teach-in/forces.html
Dr. Carlson’s Science Theater, The Bernoulli Effect – Episode 17,
http://web.ics.purdue.edu/~mjcarlso/ST/ST017_The_Bernoulli_Effect.m4v
This presentation may only be used free of charge and only for
educational purposes, and may not be sold or otherwise used
for commercial purposes
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What Do We Know About Boats?
6
What’s a Boat?
How Many Types of Boats Are There?
What’s a Sail Boat?
Are Sail Boats Important Today? – In the Past?
What Are Some Sail Boat “Pros” and “Cons”?
A Boat is a Vehicle That Floats on the Water
AND
We Control Its Speed and Direction
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What We’re Going to Do
4
Archimedes
Forces and Moments
Parts of a Boat
Design a Boat
Build & Test a Boat
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Metric System Simplified
• Key metric units are: the centimeter, gram, and second (cgs)
the meter, kilogram, and second (mks)
• Prefixes simplify quantity manipulation
kilo = 1,000
milli = 1/1000th
= 0.001
mega = 1,000 kilo
= 1,000,000
micro = 1/1000th milli
= 0.000001
giga = 1,000 mega
= 1,000,000,000
nano = 1/1000th micro
= 0.000000001
tera = 1000 giga
= 1,000,000,000,000
pico = 1/1000th nano
= 0.000000000001
UNIFYING CONCEPT
1 cc of a liquid = 1 ml of the liquid
1 ml (1 cc) of water weighs 1 gram.
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WHY THINGS FLOAT:
ARCHIMEDES PRINCIPLE
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What Keeps the Boat UP
And the Anchor DOWN?
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Density
1
• Which of these pairs is more dense:
1. A small rock or a large wad of crumpled paper?
2. A Styrofoam cup or a ceramic cup?
3. A boat that floats or a boat that sinks?
• The density, ρ (“rho”), of a material is defined as its mass, m, divided by its
volume: mass per unit of volume (g/cc):
DEFINITION
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Let’s Look At Some Densities
Substance
1. Gold
2. Lead
3. Steel
4. Aluminum
5. Ironwood
6. Sea Water
7. Water
8. Ice, Icebergs
9. Woods
• Cherry
• Oak
• Pine
• Balsa
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Which of these materials float in water?
Density: kg/m3
g/cc
19,300.
19.30
11,340.
11.34
7,800.
7.80
2,700.
2.70
1,200.
1.20
1,030.
1.03
1,000.
1.00
920.
0.92
630.
560.
500.
160.
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0.63
0.56
0.50
0.16
9
Archimedes
Archimedes of Syracuse
(287 BC – c. 212 BC)
Greek mathematician,
physicist, engineer, inventor,
and astronomer
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Archimedes Principle – Buoyancy
Kg
Kg
Volume =
3000 cc
7
7
3
3000 g of
water
kg
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Buoyancy And Archimedes’ Principle
Any object, wholly or partly immersed in a
fluid, is buoyed up by a force equal to the
weight of the fluid that the object
displaces.
Or
In Simpler Terms . . .
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Buoyancy And Archimedes’ Principle
An object with a greater density
than the fluid sinks,
AND
An object with a lesser density
than the fluid floats.
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Why Some Objects Float
ρObject
Weight
(Gravity)
(density of the object)
1
mObject
(mass of the object)
vObject
(volume of the object)
ρfluid
Original water level
(density of the fluid)
Buoyancy
“because they’re less dense than water”
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How Does This 97,000 Ton Warship Float?
1
The shape of the hull ensures 97,000 tons of water is displaced while the water level on
the outside of the hull is well below any dangerous line
By Archimedes Principle, the aircraft carrier floats
because it is less dense than water!
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FORCES
&
MOMENTS
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What are Some Common
Forces?
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What Is A Force?
In physics, a force is any external agent that
causes a change in the motion of a free body, or
that causes stress in a fixed body
Or
In Simpler Terms . . .
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What Is A Force?
It can also be described as a push or pull that
can cause an object with mass to change its
speed or direction ( to accelerate ) or which can
cause a flexible object to deform.
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Some Forces That Act on Boats
•
•
•
•
•
•
Moving water (water currents, waves)
Gravity
Buoyancy (Archimedes Law)
Wind
Friction or Drag (water, air)
Righting Force
All these forces are acting on a boat at the same time!
These forces usually create “Moments” that act on the boat.
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What’s a “Moment”
DEFINITION
A Force Acting Over a Distance
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What’s a “Moment”
Balance happens when the moments
are EQUAL
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IEEE/EIC AZ Science Center Workshop
Turning Moments and Forces
Left
Moment
Force (Weight)
Right
Moment
Force
Force
Distance
Distance
Left Moment
Exp #
1
2
3
4
5
6
=
Distance
Right Moment
Force (Weight)
Distance
Law of Moments:
F1 = Left Force
F2 = Right Force
D1 = Left Distance
D2 = Right Distance
Formula:
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IEEE/EIC AZ Science Center Workshop
Turning Moments and Forces
Left
Moment
=
Right
Moment
Force
Force
Distance
Distance
Left Moment
Right Moment
Exp #
Force (Weight)
Distance
Force (Weight)
Distance
1
2
3
4
5
6
1
5
1
5
Law of Moments:
F1 = Left Force
F2 = Right Force
D1 = Left Distance
D2 = Right Distance
Formula:
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IEEE/EIC AZ Science Center Workshop
Turning Moments and Forces
Left
Moment
=
Right
Moment
Force
Force
Distance
Distance
Left Moment
Right Moment
Exp #
1
Force (Weight)
1
Distance
5
Force (Weight)
1
Distance
5
2
3
4
5
6
2
5
1
10
Law of Moments:
F1 = Left Force
F2 = Right Force
D1 = Left Distance
D2 = Right Distance
Formula:
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IEEE/EIC AZ Science Center Workshop
Turning Moments and Forces
=
Left Moment
Right Moment
Exp #
1
2
Force (Weight)
1
2
Distance
5
5
Force (Weight)
1
1
Distance
5
10
3
4
5
6
3
5
1
15
Law of Moments:
F1 = Left Force
F2 = Right Force
D1 = Left Distance
D2 = Right Distance
Formula:
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IEEE/EIC AZ Science Center Workshop
Turning Moments and Forces
Left
Moment
=
Right
Moment
Force
Force
Distance
Distance
Left Moment
Right Moment
Exp #
1
2
3
Force (Weight)
1
2
3
Distance
5
5
5
Force (Weight)
1
1
1
Distance
5
10
15
4
5
6
4
5
2
10
Law of Moments:
F1 = Left Force
F2 = Right Force
D1 = Left Distance
D2 = Right Distance
Formula:
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Where Do You Find “Moments”?
• Some Places Where Moments are at work:
 Boats
o See – Saw
o Swing Set
o Lever
o Airplanes
o You and Me
o This Building
Almost anywhere a force is at work!
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Calculating a “Moment”
MOMENT = FORCE X DISTANCE
Force2
Force1
distance1
Moment2 = ?
Moment1 = Force1 x distance1
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distance2
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EQUAL FORCES
MOMENT = FORCE X DISTANCE
60 kg*
60 kg*
1 meter
1 meter
What are the moments?
*
The actual FORCE due to gravity is 600 Newtons
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EQUAL MOMENTS
MOMENT = FORCE X DISTANCE
60 kg*
30 kg*
1 meter
2 meters
What are the moments?
*
The actual FORCES due to gravity are 600 Newtons and 300 Newtons
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1
UNEQUAL MOMENTS
60 kg*
30 kg*
1 meter
1 meter
WhatIthappens
Rotates!now?
*
The actual FORCES due to gravity are 600 Newtons and 300 Newtons
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FLEXIBLE BODY
Force = 600 Nt
1 meter
Force = 300 Nt
2 meters
60 kg
30 kg
What are the moments?
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Moments on a Boat
(Stability)
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What Does It Mean To Be Stable?
Stability is the tendency
of an object to return to
its original state after it is
slightly moved.
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Major Parts of a Sail Boat
Hull
Keel
Rudder
Sail
Mast
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Boats in 3D!
Right Side View
Front View
Pitch Axis
Roll Axis
Yaw Axis
What Forces might
be at work in each
of these axes?
Bird’s Eye View
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1
The Keel Balances Roll Forces on a Boat
Wind
(W)
Weight of keel
righting the
boat
(G)
Wave force
tipping boat
(S)
Waves
(S)
Gravity force on
Keel
Keel
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Buoyancy force
righting the
boat
(A)
Wind force
tipping boat
(W)
Buoyancy force
on Boat
Height of mast
Depth of keel
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Ballast Stones – Roll
• Ballast is dead weight
added in the bottom of
the boat hull
• Ballast can be used in
sailboats in place of a
heavy keel to provide a
moment of force to resist
the overturning ROLL
forces from the sail
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Using The Sailor’s
Body As An
Additional
Counterweight for
ROLL stability!
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Ballast – Works for Pitch, Too!
• Wind and waves can cause
the bow of a boat to dive
into the water
• Ballast can also be used to
tune the motion of the boat
in the PITCH axis.
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Heavy
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Effects of Ballast Placement – Pitch
3
With NO Wind
Wind
Wind
Ballast
Ballast
Weight
With Wind Blowing
Wind
Wind
Ballast
Ballast
Wind
Wind
Ballast
Ballast
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Rudder – Directional Control (Yaw)
• In basic form, a rudder is a flat
sheet of material attached
with hinges to the craft's
stern, tail or aft end
• A rudder operates by
redirecting the water past the
hull, thus imparting a turning
moment to the craft
Modern ship rudder
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Rudder – Directional Control
(Cont')
Rudder
Keel
The rudder steers the boat
Without a rudder a sail boat will not move
in a straight line!
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Rudder – Direction (Yaw)
Wind
Bird’s Eye View
Water Flow
Around Boat
Ocean Waves
Turning Forces
From Wind & Waves
Rudder Force
to Stop Turn
Distance
to Rudder
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Distance
to Sail
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Capturing the Wind Force
An Old Square
Rigger
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A Modern
Catamaran
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A Modern Sailing
Yacht
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Capturing the Wind Force
• The wind force on the boat is due to the pressure of the wind on the sail
• The force is proportional to the wind speed and Pressure (W) and the sail
area
a
2m
Wind Pressure (W)
Sail
a
2m
Wind Pressure (W)
2a
4m
Sail
Sail Area = a x a = (a2)
= 2 x 2 = 4 sq. m
Force ~ W x a2 = W x 4 Nt.
Sail Area = 2a x 2a = 4a2
= 4x x = 16 sq. m
Force ~ W x 4a2) = W x 16 Nt.
= 4 x (W x 4) Nt.
2a
4m
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Drag Is The Friction Between The
Water or Wind And The Boat
WIND
FORCE ON
SAIL
FORWARD
MOTION OF
BOAT
DRAG FROM WATER & WIND
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Controls Summary
Roll
Keel / Ballast
Pitch
Keel / Ballast
Yaw / Direction Rudder, Keel
Speed
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Sail, Drag
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Parts Of A Sailboat
Fill in the Blanks
5
All sailboats have five basic
components:
• The Hull supports the mast,

rudder, and cargo.
• The Mast

supports the sails.

• The Sail catches the wind
and provides the force to move
the boat.
• The Keel or Ballast stabilizes

the hull in roll and pitch.
• The Rudder is used to steer

the boat.
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Hull
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Design a Boat
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Elements Of A Sail Boat Design
• Float:
– Buoyancy → Density → Archimedes → Hull
• Not tip – Be stable:
– Righting Moment → Keel or Ballast
• Speed:
– Wind Force → Wind Speed and Area → Sail and Mast
• Go Straight:
– Balanced Forces → Steering → Rudder
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Engineering Trade-Offs
Speed
Sails / Drag
Direction
Stability
Rudder / Sails
Hull / Ballast / Keel
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Forces on Sail Boats
WIND
EXERTS
FORWARD
FORCE ON
SAIL
SAIL PUSHES
BACK ON WIND
Weight
SAIL PULLS ON
MAST AND PULLS
BOAT FORWARD
DRAG FROM WATER
RESISTS FORWARD
MOTION OF BOAT
Buoyancy
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Design a Boat
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Build and Test a Boat
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Materials for Boat Building
Water Bottles
Barbeque Skewers
Tooth Picks
Foam Core Boards
Rubber Bands
Clear Tape
Plastic Sheets
Twist Ties
Gravel
Construction Paper
String
Aluminum Foil
Plastic Food Wrap
Paper Clamps
Twist Ties
Tools for Boat Building
Pencil
Paper
Scissors
Paper Punch
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The Objectives
Design and Build a sail boat that:
A. Goes Straight
B. Goes Fast
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The Design Guide
• Page 1 – Hints
• Page 2 – Your design
– Plan your concept. Consider stability, speed, direction, cargo capacity
– Use the design Triangle: Stability, Speed, Direction
– Include all the parts: hull, mast, sail, keel, rudder
• Page 3 – Testing: Stability, Direction, Speed
– Test and adjust as you go
– Observe what others are doing to “fix” their problems
• Page 4 – Record your observations
– What worked -- What didn’t work
– What discoveries did you make
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The Rules!
•
•
•
•
•
•
•
•
Work in teams of two
You can use any of the materials laid out on the tables
Keep in mind that all your parts will be exposed to water
Your design has to operate in the test pool for at least three
minutes without falling apart
It may have to carry a load of steel washers from one end of the
pool to the other
Be sure to watch the tests of the other teams and observe how
their different designs worked
After testing your first design, see if you can improve the design to
overcome the deficiencies you noted
Make and test as many different sail boat designs as you have time
for
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Let’s Build
And Test
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Sail Away
Review
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What We’ve Done
Archimedes
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What We’ve Done
Archimedes
Forces and Moments
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What We’ve Done
Archimedes
Forces and Moments
Parts of a Boat
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What We’ve Done
Archimedes
Forces and Moments
Parts of a Boat
Design a Boat
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What We’ve Done
Archimedes
Forces and Moments
Parts of a Boat
Design a Boat
Build & Test a Boat
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Questions?
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SAIL AWAY
MOTION AND FORCES
Institute Of Electrical And Electronics Engineers, Phoenix Section
Teacher In Service Program / Engineers In The Classroom (TISP/EIC)
“Helping Students Transfer What Is Learned In The Classroom To The World Beyond”
SEPTEMBER 2011
AZ Science Lab
79