Floating
and
Sinking
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Explaining Floatability
3.1 Changing Floaters and sinkers

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How much cork could a nail sinker sink if a nail sinker could sink cork?

Key:

a b c d e f g h i j k l m

aİİİbİİcİİİdİİİeİİİfİİgİİİhİİİİ iİİİ jİİİkİİİ lİİİİm

n o pq r s t u v w x y z

nİİİoİİİpİİİqİİrİİİsİİİtİİİuİİİvİİİwİİİxİİyİİz

Observations and Data Table:
Size of Cork
Number of Nails Needed
?
to Sink the Cork
İ
İ
The small cork takes less nails to

sink than the larger cork.

Conclusion:

Big corks are more buoyant because it takesmore ballast to sink them.İ The cork sinks when the nail ballast makes the weight stronger than the buoyant force of the water.

The small cork takes less nails to sink than the larger cork.

Conclusion:

Big corks are more buoyant because it takes more ballast to sink them.

The cork sinks when the nail ballast makes the weight stronger than the

buoyant force of the water.

3.2A Testing Stacia's Hypothesis:

(pp 88-92 modified for organization support only)

The question that comes from the dialogue cartoon on p88 is, "How does the mass of a floating liquid compare with an equal size of water?"

Hypothesis: Alcohol floats because it has less weight than the same volume of water.

(A liquid floats because it has less weight than the the same volume of another liquid.)

Data Table:
Liquid
(equal volumes)
50mL
Weight
Floating Order
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İ
Top #1
İ İ
İ
Bottom #5
İ İ
İ İ
Conclusion:

A liquid floats because it has _________ weight than the same volume of another liquid. (more, less)

3.2B Testing Stacia's Hypothesis: Exploration-4 p89

Question investigated: Will wood or other floaters have less weight than equal volumes of water?

Hypothesis: Wood will float because it has less weight than an equal volume of water. (See notes p 90 "Using an overflow can")

Data Table:
Set Zero on scale
Weight of wood
Weight of an equal volume of water
(Weight of displaced water)
I
zeroed
İ
İ
N
Conclusion:

The hypothesis is correct because wood floats when it has ____ mass than an equal volume of water. (less, more, equal)

Will metal bolts sink because they have more mass than equal volumes of water? (see Exploration 8)

3.3 An Explanation Check - Exploration-5 p91

Question investigated: How does the weight of water displaced affect the floatability of an object?

Hypothesis: A metal bolt sinks because it has more weight than an equal volume of water.

Data Table:
Set Zero on scale
Weight of Bolt
Weight of an equal volume of water
(Weight of displaced water)
ßzeroed
İ
N
N
Conclusion: Metal bolts sink because they have _________ weight for equal volumes of water. (more, less, equal)

ARCHIMEDIES
(ARCHIMEDIES)

3.4

WHILE SITTING IN THE BATH ARCHIMEDIES. . .Solve and Read the text below.

Greek Key:

a b c d e f g h i j k l m

a b c d e f g h i j k l m

n o p q r s t u v w x y z

n o p q r s t u v w x y z

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An educated Greek named archimedieslived in Syracuse on the island of Sicily in the third century B.C. King Hiero II had a beautiful new gold crown made. He suspected the goldsmith hadtaken his gold and mixed it with silver. Archimedies was asked to proove it.

Archimedies was baffled. Then, one day Archimedesnoticed water rose in the

bath as he lowered himself into the water. When the water rose he felt lighter. Archimedes was beside himself.

"eureka!, eureka! ", he shouted as he streaked home

through the streets of Syracuse.

"Eureka!", is Greek for, "I found it." Whathe found was open to many interpetetions Ö The story goes he discovered how to test the purity of gold in King Hiero'snew crown without destroying it.

Solution:

An educated Greek named Archimedies lived in Syracuse on the island of Sicily in the third century B.C. King Hiero II had a beautiful new gold crown made. He suspected the goldsmith had taken his gold and mixed it with silver. Archimedies was asked to proove it.

Archimedies was baffled. Then, one dayArchimedies noticed water rose in the bath as he lowered himself into the water. When the water rose he felt lighter. Archamedies was beside himself. "Eureka!, Eureka! ", he shouted as he streaked home through the streets of Syracuse.

"Eureka!", is Greek for, "I found it." What he found was open to many interpetetions Ö The story goes he discovered how to test the purity of gold in King Hiero's new crown without destroying it.

What do you think Archamedies solution was?

(On page 113 in your book you can see Archamedies solution.)

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3.4B Archimedies

Hypothesis:Liquids with more mass for an equal volume float things better.
Circle the straw below with the correct floating height
Conclusion: Liquids with a larger upward force have _________ mass for equal volumes. (more, Less)

3.5 Why boats Float

.51 Try this: Floating Foil

.52 Try this: Floating Bottles

.

3.5 Why boats Float

.53 Try this: Bobbing Corks

.54 Try this: container-sinker in one volume floater in another

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3.5 Why boats Float

.55 Try this: Mystery Straws
Each silicone sealed straw 

has the same ballast weight. 

Observation 

The small one _______ whileİ 

(sinks/floats)İ 

the larger one _______ 

(sinks/floats) 

Conclusion: 

The larger one _____ because: 

(sinks/floats) 

________________________________________________________ objects, with _______ 

(Large,Small) (bigger, smaller) 

volumes float better.

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3.5 Why boats Float

.56 Try this: Make a Prediction.

Shade in the water level in the second overflow can. Then try it.

A clay ball and the clay boat are made from the same amount of clay as follows:

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Data:

The clay ball displaces _____ mL of water

The clay boat displaces _____ mL of water

Conclusion

Better floaters displace ________ water.

(more, less)

3.5 Why boats Float

Summary cryptogram

Key:

a b c d e f g h i j k l m

a b c d e f g h i j k l m

n o p q r s t uv w x y z

n o p q r s t u v w x y z

Summary:

The activities which you have just finished all show

larger objects float

better than small.If a small

thing sinks then make it larger to float it.

3.6 Application-1

.61swimming and diving)

There are many examples of this in your everyday life. Place one arm behind your chest and the other in front. Breath in and out slowly. Your chest becomes larger when you breath in,smaller when you breath out. Now think of what you do when you want to dive or crawl along a pool bottom. Breathing out air makes your body volume smaller and allows you to sink. This simple idea has been expanded in the technology of making better life jackets. Life jackets all have one thing in common they give the body a larger volume to displace more water. This causes the body to float.

3.6 Application-2:

.62(boats and rafts)

If you are going boating you must have a large enough boat for safe fun. Because larger boats float better. Think of the size and shape of ships which carry heavy cargo. Why must they be so large?

When you build a raft you choose small logs. They are easier to handle but they won't carry much weight. If you hope to float you use many small or large logs. Extra logs give the raft more volume. This allows it to displace more water and float better Water pleasure craft often have floatation devices under seats and behind bulkheads. This bulk foam helps keep the craft afloat in the event of an accident. The foam floatation helps the craft displace more water. Have you heard of plans to raise ship wrecks or seen movies of raising planes lost in the ocean? the air bags float the wreck as they add extra volume.

Summary: Answers

The activities which you have just finished all show

larger objects float better than small.If a small thing sinks then make it larger to float it.

Application-1: (swimming and diving)

There are many examples of this in your everyday life. Place one arm behind your chest and the other in front. Breath in and out slowly. Your chest becomes

larger when you breath in,smaller when you breath out. Now think of what you do when you want to dive or crawl along a pool bottom.

Breathing out air makes your body volumesmaller and allows

you to sink.

This simple idea has been expanded in the technology of making better life

jackets. Life jackets all have one thing in common they give the body

a larger volume to displace more water. This causes the body to float.

Application-2: (boats and rafts)

If you are going boating you must have a large

enough boat for safe fun. Because

larger boats float better. Think of the size and shape of ships which carry

heavy cargo. Why must they be so large?

When you build a raft you choose small logs. They are easier to handle but they

won't carry much weight. If you hope to float you use many small or

large logs. Extra logs give the raft more volume. This allows it to

displace more water and float better

İ

Water pleasure craft often have floatation devices under seats and behind bulkheads. This bulk foamhelps keep the craft afloat in the event of an accident.

The foam floatation helps the craft displace more water.

Have you heard of plans to raise ship wrecks or seen movies of raising

planes lost in the ocean? the air bagsfloat the wreck as they

add extra volume.

3.63 Dancing Mothballs (observation and application)

Method:

Add two large spoons of baking soda to 2L of water. Stir until the soda dissolves.

Add 30-50 mL of vinegar and stir once.

Drop in 4-5 mothballs
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Observations: 

[1] Watch the mothballs for a while 

[2] When a moth ball comes to the surface watch it's motion then, jab it quickly with a pencil. 

[3] Draw arrows near each numbered mothball (1, 2, 3, 4, ) in the pictureİ 

İ 

This will show what the mothball is probably doing.

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Conclusions:

Key:

a b c d e f g h i j k l m

a b c d e f g h i j k l m

n o pq r s t u v w x y z

n o p q r s t u v w x y z

Conclusions: Dancing Mothballs

The mothballs float when they collect many

bubbles to displace more

water.

The mothballs sink when their coat of bubbles is

thin because they displace

less water.

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The mothballs with bubbles float better because the

waterproof bubbles act like a lifejacket causing the

mothballs to displace more

water.

İ

The bubbles floating by themselves throughout the water are not important in

changing the upward push of the liquid because the

mothballs do not go up and down

altogether

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Answers: (Conclusions to Dancing Mothballs)

The mothballs float when they collect many bubbles to displace more water.

The mothballs sink when their coat of bubbles is thin because they displace less water.

The mothballs with bubbles float better because the waterproof bubbles act like a lifejacket causing the mothballs to displace more water.

The bubbles floating by themselves throughout the water are not important in changing the upward push of the liquid because the mothballs do not go up and down altogether

3.71 Why boats Float Part 2 modified p107
First -1
then -2
then-3
then-4
then-5
Data:
İ
Floater
Ballast is changed
for each
Trials
(other floaters and semi-submersible
can also be tried)
Weight? (N)
Weight? (N)
İ İ
İ İ
İ İ
İ

Conclusion: Boats float because the weight of the water displaced is _______________ the weight of the floater. (same as, more than, less than)

This helps explain how to adjust a semi-submersible floating level. When extra ballast is added the rig sinks until the weight of the water displaced is _____________ the weight of the extra ballast.(same as, more than, less than)

This helps explain how a boat can be overloaded also.The mass of a boat causes it to displace water.

3.72 Back to the Straws

Place the weighted straws at the left at the correct floating level in the test tubes. (Notice all the test tubes have the same liquid in them.

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The straw with _________ nails for ballast will displace _________ (more, less) (more, less)

water and _________sink deeper.

(will, will not)