Download The Properties of a Physical Body

The Physics of Sound:
Background Principals Necessary to the
Understanding of Sound and Waves
Part One:
The Properties of a Physical Body
Concepts Covered in this Package:
Mass, Weight, Inertia, Elasticity and Mediums
Unit: Sound and Waves
Background Principals Part One: The Physical Properties of a Body
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A
Allll A
Arrtt B
Beeggiinnss W
Wiitthh IIttss M
Maatteerriiaallss .. .. ..
“Aboriginal music, both traditional and modern, is unique. It has always underlined the
tactile bond between the instrument and the musician. All art begins with its materials.
Creating a drum, tuning it and caring for it teaches the drummers to recognize the basic
physical qualities that they must understand and the skills that they must master.
“Just as sharing knowledge binds musicians to their cultural and geographical world,
constant practice binds them to the physical world. The drum maker and the drummer
might or might not be the same person, but always they are one spirit. They must know
the materials’ unique qualities and the sounds they make – in short, they must know the
physics with which they work to develop their craft. The modern powwow drum’s sound
that Gabe prefers is far deeper than a traditional powwow drum’s higher pitch. Drum
makers achieve both sounds because they have manipulated a few basic physical
qualities. Yet, those small differences have developed over thousands of years; through
many generations of cultural evolution.”
Clealls (Dr. John Medicine Horse Kelly) and Andrew Tracy, Native Drums Website
T
Too U
Unnddeerrssttaanndd aann IInnssttrruum
meenntt iiss ttoo R
Reessppeecctt IItt .. .. ..
“Before it is a celebration, a religious ritual, a social practice or an art, Aboriginal music
– all music – is a set of practical skills musicians learn so they can understand their
instruments. This knowledge is an important part of respecting Natural Law: a way of
living that means so much to Native cultures and communities. To become one with an
instrument is to respect it. The honour the listeners pay the instrument radiates through
the community. Thus, the skills a musician seeks are both a personal pursuit and a means
of connecting with the community. Our cultural rules are precise, but, music crosses
cultural lines. Songs, dances and stories embrace the full continent; what the Eastern
North American Anishinabe call Turtle Island.”
Clealls (Dr. John Medicine Horse Kelly) and Andrew Tracy, Native Drums Website
Unit: Sound and Waves
Background Principals Part One: The Physical Properties of a Body
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The Properties of a Physical Body
Concepts Covered in this Package:
Mass, Weight, Inertia, Elasticity and Mediums
Introduction
Scientists know that the disembodied strains of music that reach our ears, drifting
invisibly in the air around us, are the result of the same laws of physics that govern our
lives and movements in the natural world. In short, music itself is subject to the same
forces that keep the Universe in balance and affect our very lives. Therefore, the “how”
and “why” of music is in harmony with the laws of physics. These laws enable us to
create the sounds that for many thousands of years have inspired musicians and listeners
alike.
The Properties of a Physical Body
Consider now, the physics of items that musicians have used to create musical sound.
Among them are the skin of the drum, the strings and box of the violin, the long tube of
the flute, the pebbles and hide of the rattle as well as the air with which all these parts are
in contact. The following are the basic qualities possessed by every physical body:
Mass, Weight, Inertia, Elasticity, (occupies a) Medium.
Mass, Weight, Inertia, Elasticity and Medium
Mass is how much matter an object contains. The most common measurements are the
gram (g) and the kilogram (kg).
Weight refers to how much force gravity exerts on an object’s mass, that is, the
downward pull that keeps the body connected to the earth’s surface. The mass of an
object will always remain constant, but its weight can change if this gravitational pull
changes. In outer space, for example, an object keeps its mass, but becomes weightless.
Its innate essence remains the same regardless of its interactions with other influences.
“Both scientific and Aboriginal teachings embrace this principle. The forces that change
our true nature are not external. They must come from within.”
Clealls (Dr. John Medicine Horse Kelly), “Secrets of Sound,” Native Drums Website)
Unit: Sound and Waves
Background Principals Part One: The Physical Properties of a Body
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Formula for Weight:
-
W=mxg
W = weight, m = mass (in kg) and g = gravitational acceleration (m/s2)
Weight is measured in Newtons (Newton = kg. m/s2)
Gravitational acceleration on earth: g = 9.8 m/ sec2)
Inertia is that property of a body that resists changes in its motion. If an object is at rest
it will remain at rest, and if in uniform motion along a straight line, it will remain in that
motion until an outside force or forces acts upon it.
So, inertia raises two possibilities:
1. If an object is not moving it will stay perfectly still until something makes it
move.
2. If an object is moving in a straight line it will keep going forever unless
something makes the object change its velocity or direction.
Elasticity is that property of an object that allows an outside force to deform it from its
original state without breaking it. It then allows the object to return to its original state
once the outside force has been removed. When anything produces a sound, elasticity
plays an important role. However, elasticity does not apply to media such as air.
The medium is the material through which vibrations move from one place to another.
Medium comes from the Latin word medius, which means “middle.” So, think of a
medium as the middle, or go-between, for bringing vibrations from an instrument to your
ears. It can be a liquid, such as water; or a gas, such as air. All musical instruments –
drums, stringed instruments, flutes and others – produce the vibrations we hear as sound.
The music is the sound source and air is the medium, just as for humpback whales the
medium is water.
Unit: Sound and Waves
Background Principals Part One: The Physical Properties of a Body
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Test Your Understanding About
the Properties of a Physical Body:
*To read more about the examples of native drums used below, see “Real Life Applications
of Science: Excerpts from the Native Drums Website”.
1. Which has more mass?


A large powwow drum (played by several people at once)
A “single head” hand drum
2. Which would weigh more?


A body on Earth (g = 9.8 m/s2)
A body on Mars (g = 3.7 m/s2)
3. Which is NOT an example of a box drum in equilibrium?


A box drum suspended from the ceiling, not in use.
A box drum being played.
4. The hand drum used by First Peoples is typically made by stretching a thin piece
of animal skin over a very thin plank of wood bent into a circular frame. Which
part of this hand drum best exemplifies the property of elasticity?


The thin piece of animal skin stretched over the thin plank of wood.
The thin plank of wood bent into a circular frame.
5. Which of the following would result in NO SOUND:



A hand drum placed in an airtight container with ABSOLUTELY NO AIR;
A hand drum placed in an airtight container with LOTS OF AIR;
A hand drum placed in an airtight container with JUST A BIT OF AIR.
6. Which of the following would result in the LOUDEST SOUND:



A hand drum placed in an airtight container with ABSOLUTELY NO AIR;
A hand drum placed in an airtight container with LOTS OF AIR;
A hand drum placed in an airtight container with JUST A BIT OF AIR.
Unit: Sound and Waves
Background Principals Part One: The Physical Properties of a Body
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7. True or False: Sound needs a medium through which to travel. Without a
medium, no sound exists.


True
False
*Check your answers. Correct answers located on last page.
Unit: Sound and Waves
Background Principals Part One: The Physical Properties of a Body
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Real Life Applications of Science:
Excerpts from the Native Drums Website
Powwow Drums
-
-
In the Plains region, drum groups use large, coffee table-size drums during powwow
ceremonies. The group has numerous members all of whom play the powwow drum
at the same time.
The powwow brings all peoples together. It is also a symbol of First Peoples’
solidarity and a way for Native people to express their cultural heritage.
Hand Drums
-
Many First Nations use hand drums for various occasions and ceremonies.
One example is the “single head” hand drum that Mi’kmaq First Peoples of
Canada’s maritime provinces use.
-
Another example is the octagonal-shaped hand held drums that various nations use.
-
Ojibwe First Peoples traditionally used hand drums. They make the drum heads of
deer or moose hide, and use birch bark for the body. Over time, they began
participating in powwow events, and now create and use the larger Plains-style
drums as well.
-
The Tlingit of the Northwest Coast region of Canada, use ornately decorated hand
drums that they paint with their crests and totems on the inside, where it will not be
worn off by the constant beating with a drum stick.
Other coastal peoples, including the Haida, Tsimshian, Kwakw’aka’wakw and the
Coast Salish also ornately paint their crests and totems on their hand drums. But,
they usually paint the drum heads on the outside using very durable paints that can
withstand constant drumming.
-
A special type of hand drum is the water drum, used mainly by Haudenosaunee and
Ojibwe Peoples.
-
Inuit and Inuvialuit First Peoples use very large hand drums with handles. A
variety of materials are used for the construction of these drums, such as the skin of
deer, caribou and mountain sheep, as well as the intestines of whale or walrus. Antler
and bone are used for the drum beaters.
During the past century however, cloth and nylon have sometimes been used instead
Unit: Sound and Waves
Background Principals Part One: The Physical Properties of a Body
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of animal skins to construct the drumheads. These drums usually do not carry the
same sacred significance as skin drums.
Box Drums
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Some First Nations in the Northwest Coast region use huge box drums. This drum
resembles a large, flat, wooden box and is often made of red cedar. These drums do
not have a membrane like the powwow and hand drums. To play the drum, it is
suspended from the ceiling, and pounded only with a fist wrapped in cedar bark.
Drummers have to find just the right spot to make these drums resonate.
Suggested Reading:
“Aboriginal Music and Physics,” by Clealls (Dr. John Medicine Horse Kelly) and
Andrew Tracy, “Secrets of Sound,” Native Drums Website
Unit: Sound and Waves
Background Principals Part One: The Physical Properties of a Body
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Answers
1.
2.
3.
4.
5.
6.
7.
A large powwow drum (played by several people at once)
A body on Earth
A box drum being played
The thin piece of animal skin stretched over the thin plank of wood.
A hand drum placed in an airtight container with ABSOLUTELY NO AIR
A hand drum placed in an airtight container with LOTS OF AIR
True
Unit: Sound and Waves
Background Principals Part One: The Physical Properties of a Body
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