Chapter 15 Supplement HPS
Harmonic Motion
Motion
 Linear
 Harmonic
 Moves from one
 Motion that repeats
place to
over and over again
another
 Examples
 time, speed,
acceleration
 Examples
 Pendulum
 Swing
 Pedaling on a cycle
Harmonic Motion
Nature
Art / Music
Technology
Pendulum
Light
Cell phones
Heart
Sound
Radio waves
Color in light
waves
Clocks
Electrons
Earth
- 4 oscillators
Evidence of WAVES
 See vibrations
 Makes or responds to sound or lights
 Transmits info through the air w/o wires
 Allows you to “see through” objects
Electromagnetic spectrum
2 Types of Waves
 Transverse


Oscillate perpendicular
to the direction of the
wave
Ex: water
 Longitudinal


Oscillate parallel to the
direction of the wave
Ex: compressional
Properties of Waves
 Amplitude: the height of the wave (m)
 Wavelength: the distance between adjacent crests (m)
 Period: the time it takes for one complete wave to pass a
given point (sec.)
 Frequency: the number of complete waves that pass a
point in one second (1/sec or Hz)
 Speed: the horizontal speed of a point on a wave as it
propagates (m/sec) (frequency x wavelength)
Properties of Waves
Crest
“S”
Trough
Terms
Harmonic motion is a repeated sequence of cycles.
Period – time for 1 cycle. (sec.)
Frequency - # cycles per second. (Hz)
Amplitude – Size of the cycle (degrees, length, voltage, pressure)
Basic characteristics of waves
 Node
 Points where the string
does not move
 Anti-node
 Points where the string
moves the most
What harmonic?
RESONANCE
 These Standing Waves occur at what are
called Natural Frequencies or Harmonics
 Every object, substance and material has
its own Natural Frequencies, where it
“likes” to vibrate
 All Natural Frequencies are multiples of
the Fundamental
Natural Frequency
 Know how it will vibrate
 Know what kind of waves
it makes
 Depends



Tension
length
weight of string
Resonance
 Having the natural
frequency just in tune
with your force
 Each force adds to the
system
 Transfer of Power
 Swing

Each pump adds to the
last and the amplitude
grows
Tacoma Narrows Bridge
 1940 – 4 months after completion
 Destroyed by wind generated resonance
 Mild gale produced an irregular force in
resonance with the natural frequency of
the bridge, steadily increasing the
amplitude of vibration until the bridge
collapsed.
Interference
Patterns on the String
Standing
Wave
Patterns
Calculate
Wavelength?
(λ)
Lab:
v=fλ
 Each Harmonic has a different frequency and
wavelength
 Hz x λ gives the same answer for ALL
Harmonics
 Cycles/Seconds x Meters/Cycle= Meters/Second
which is a value for speed of the Wave on the
string
 If Frequency
, Wavelength
Wavelength
T = 1/f
and if Frequency
Harmonic Motion Graphs
energy / amplitude?
Independent variable:
Dependent variable:
X- axis:
Y-axis:
Damping
What causes the damping in each situation?
Damping
http://physics.bu.edu/~duffy/semester1/c19_damped_sim.html
ENERGY INTERATIONS
•ABSORPTION
•REFLECTION
•DIFFRACTION
•REFRACTION
ENERGY INTERATIONS
•ABSORPTION
•REFLECTION
•DIFFRACTION
•REFRACTION
ENERGY INTERATIONS
•ABSORPTION
•REFLECTION
•DIFFRACTION
•REFRACTION
ENERGY INTERATIONS
•ABSORPTION
•REFLECTION
•DIFFRACTION
•REFRACTION
Chapters 15.3 & 16.1 HPS
Sound & Waves
Range- 20 – 20,000
Hz
HIGH
Hairs
Fluid-Filled
Hearing and
Balance
EAR DRUM
Best Range- 100-2,000 Hz
LOW
 LAB DEMO: FEEL THE AMPLITUDES
(1) FREQUENCY CHANGES and (2)VOLUMES
 Radio loudspeaker is a paper cone that vibrates in
rhythm with an electrical signal. (wavelength)
 Air molecules are set into motion – vibrating into other
molecules. They vibrate from the speakers into the
room – setting the room air molecules into motion
which collide into our eardrum.
Speakers
Lab – Properties of Sound
 Section 1 (Teacher demonstrated LAB)
440.0
 Consonance

Sounds GOOD
441.0
 Dissonance
 Sounds BAD
Answer: BEATS (DISSONANCE)
Results when 2 frequencies are close.
440.0
441.0
Lab DEMO – Properties of Sound
WAVELENGTH
 Section 2 Sound gets louder then softer WHY?
(constructive and destructive interference)
Move speaker forward
IN
PHASES
 OUT
Partially out of Phase
Softer Sound
- High Freq.
- High Pitch
- Waves closer
together
- Low Freq.
- Low Pitch
- Waves farther
apart
Frequency and Pitch
Lab 13.2 – Properties of Sound
 Section 3
Which has a HIGHER Frequency?
Which has a LOWER frequency?
A
B
C
Lab 13.2 – Properties of Sound
 Section 3
Which had a HIGHER Frequency?
Which had a LOWER frequency?
A
B
C
Lab 13.2 – Properties of Sound
 Section 5
 Which wine glass
had a HIGHER
frequency?
 LOWER
frequency?
 What is vibrating?
Lab 13.2 – Properties of Sound
 Section 5
 Which wine glass
had a HIGHER
frequency?
 LOWER
frequency?
 What is vibrating?
WATER
Lab 13.2 – Properties of Sound
 Section 6
 Which bottle had a
HIGHER
frequency?
 LOWER
frequency?
 What is vibrating?
Lab 13.2 – Properties of Sound
 Section 6
 Which bottle had a
HIGHER
frequency?
 LOWER
frequency?
 What is vibrating?
AIR
Air Pressure
 Loud
High
Pressure
 Soft
Low
Pressure
HARMONIC MOTION – is an oscillation in
pressure and the wave produced is a sound
wave.
Decibel Scale (dB)  Measures
 Relates to
amplitude of
the wave
 Most sound
between 0-100
 Every 10dB
increase
sounds about
2xs as loud
loudness
Sound Waves
 Alternating high and
low pressure
 Anything that
vibrates creates
sound waves
 Longitudinal Wave
(air is compressed)
The speed of sound in other
materials is often faster than in air.
No sound in outer space.
 Speed 340 m/s (660 mph)
 Depends on
 Temperature
 Cold / slower
 Hot / faster
 Kind of molecule
 Heavier / slower
 Lighter / faster
 Restoring Force
 Smaller / slower
 Bigger / faster
Speed of
Sound Waves
Supersonic Speed
 Motion faster than sound
 Passenger jet - Concorde
SHOCK WAVE
NOISE !
QUIET
Acoustics
The science and technology of sound
Reflection
Diffraction
Each of these can be done
with a certain degree of
success
Absorption
To stop sound – dense thick wall materials
Concert Halls
 Reverberation – multiple echo
results when waves bounce off
of hard surfaces
 The right amount is good –
sound livelier and richer
 Also causes interference –
could result in “dead spots”
(destructive interference)
Frequency and Sound
 Fundamental
Harmonic (A)
 2nd (B)
 3rd (C)
 4th (D)
(A)
(B)
(C)
Amplitude (cm)
(D)
(E)
 5th (E)
Frequency (Hz)
Understanding Sound Waves
 SONOGRAMS
Freq (Hz)
 Graph that shows
how loud “sound” is
at different freq.
 ULTRASOUND
 High Freq creates
images of body
 WHITE NOISE
 Equal mixtures of
all frequencies
Time (sec)
END
Note Name Frequency C major
C
D flat
D
E flat
E
F
G flat
G
A flat
A
B flat
B
C
264
285
297
317
330
352
380
396
422
440
475
495
528
Yes
Yes
T
u
n
i
n
g
Yes
N
o
t
e
s
C minor D major
Yes
Yes
Yes
Yes
Yes
Yes
Optional Optional
f
o
r
C
h
o
r
d
s
Sound and Music - Chords
 Different notes have different
frequencies
 Chords are combinations of different
notes with specific mathematical
relationships
 Different relationships of the notes will
produce chords with very different
“moods” or “feel”
Note Name
Key Color
Frequency
C
528
B
495
B flat
A
475
440
A flat
422
G
396
G flat
380
F
352
E
330
E flat
D
D flat
C
317
297
285
264
HAPPY BIRTHDAY
Melody
Harmony
Melody
Harmony
C C D C F E
A
A Bb
C C C A F E D
F
C Bb
C C D C G F
Bb
Bb A
Bb Bb A F G F
C
A
TWINKLE, TWINKLE LITTLE STAR
F F C C D D C
Bb Bb A A G G F
Harmony C C A A Bb Bb A
G G F F E E C
C C Bb Bb A A G
C C Bb Bb A A G
Harmony A A G G F F C
A A G G F F C
Melody
F F C C D D C
Bb Bb A A G G F
Harmony C C A A Bb Bb A
G G F F E E C
Melody
Melody
GOD BLESS AMERICA
Melody
F E D E D C
Harmony A C
Harmony
Melody
E
E D E F
Bb A C F G A
Melody
C
E F G C
Harmony C
E
G A Bb D
G F G A
D
G F G F E F
F
E
C
F GA C
G A Bb E A Bb C
D
E
F
Melody
D C Bb A G F
Bb A G F
Harmony
F F E C E D
F F E C
G C
G