Transcript Fund Def - Chemistry at Winthrop University

PHYS 256
Musical Acoustics
Syllabus
http://bohr.winthrop.edu/faculty/mahes/link_to_webpages/cou
rses/phys256/phys256home.html
Textbook
The Physics of Sound,
3/E
Richard E Berg
David G Stork
Richard E. Berg: B.S, M.S, Ph.D; Professor of Physics, University of Maryland.
B.S in Music with emphasis on piano and clarinet.
David G. Stork: B.S, M.S, PhD; Chief Scientist, Ricoh Innovations, Inc.
Accomplished orchestral and chamber timpanist/percussionist.
Instructor
Ponn Maheswaranathan: B.S, M.S, PhD; Professor of Physics, Winthrop
Native of Sri Lanka, Naturalized U.S. citizen
Fundamental Definitions
1.
2.
3.
4.
5.
6.
7.
8.
Position, Length, Distance
Time
Velocity or Speed
Acceleration
Mass
Density
Force
Pressure
Position, Length, Distance
1. Cartesian Coordinate System (x and y)
2. Prefixes
3. Metric System
http://physics.nist.gov/cuu/Units/index.html
Time
1. Time interval can be measured using the
following units: second, minute, hour, day,
month, year, etc.
2. The following smaller units are also used:
millisecond (ms), microsecond (µs).
3. Calculate the period (T) of a 440 Hz tone.
Speed and Velocity
Speed = Distance/Time
Velocity = Speed + Direction.
Speed of sound in air = 345 m/s = 1100 ft/s
Speed of light = 3x108m/s = 186,000 miles/s.
Acceleration
• Acceleration is the rate at which velocity
changes.
v v  v0
a

t
t
Units: m/s2, cm/s2
Acceleration due to gravity = g = 9.8 m/s2.
Mass
Mass is a measure of the amount
of matter contained in an object.
Examples of Mass
A massive supertanker, for instance, is one that contains
an enormous amount of mass. In comparison, a penny
does not contain much mass. Mass is a scalar quantity.
Mass Density
The mass density r is the mass m of a substance
divided by its volume V:
SI Unit of Mass Density: kg/m3
Linear and areal Density
Linear density of stretched wires is important
in the design of stringed instruments.
Linear Density = Mass per unit length.
Areal Density = Mass per unit area.
Force
In common usage, a force is a push or a pull.
Forces can be categorized as,
Contact forces and Non-Contact forces.
Newton's Second Law of
Motion
Newton’s second law is a relationship between acceleration,
forces, and mass.
When a net external force acts on an object of mass m, the
acceleration a that results is directly proportional to the net
force and has a magnitude that is inversely proportional to the
mass. The direction of the acceleration is the same as the
direction of the net force.

a


F
m

SI Unit of Force: : kg · m/s2 = newton (N)


F  ma
Weight
Weight is the force of gravity.
Weight = Mass x Acceleration due to gravity.
On the moon, your weight will be 1/6th of that
of Earth weight, because the acceleration
due to gravity is 1/6th of that of Earth’s.
http://www.splung.com/content/sid/2/page/gravitation
Units
Quantity
SI unit
Vector or Scalar
Pressure
People who have fixed a flat tire know something about pressure.
In colliding with the inner walls
of the tire, the air molecules
(blue dots) exert a force on
every part of the wall surface.
Pressure
The pressure P exerted by a fluid is defined as the magnitude F of the force
acting perpendicular to a surface divided by the area A over which the force
acts:
The SI unit for pressure: newton/meter2 = (N/m2) = pascal (Pa).
Pressure Illustration
Human Ear
Rapid changes in air
pressure cause
vibrations of the
eardrum, which we
hear as sound.