# 05notes.ppt - Oak Ridge Schools by wulinqing

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```									 General Physics
Oak Ridge HS
Mr. M. Perkins • Ms. C.J. Pina
Monday, August 17, 2009
Introductions and Notecards

Last Name, First Name                                 Period
City, State, Zip
Your lunch period (4th or 5th)
Current math class
Extracurricular activities (sports, music, arts)
One thing I should know about you is…
Science Autobiographies
 1st Paragraph –
Tell me about yourself, where you were born, brothers
and sisters, favorite color, what you want to be when
you finish high school.

 2nd Paragraph –

 3rd Paragraph –
Tuesday, August 18, 2009

LAB: Designing an Experiment
 Next, set up your lab book as follows
 Date in the upper right corner
 Title centered at the top of the page
 Add the following, starting from the left margin below
the title
Partners: (the people at your table)
Objective: To design an experiment to collect and
analyze data on poppers.
Materials: (leave blank for now… allow two lines)
Procedure:
Wednesday, August 19, 2009
Investigate – Setting up your notebook
 3a) Table – Length of string varies, mass the same
Make a general statement about what happens to the pitch
you hear as you change the length of the vibrating string.

 5a) Table – Mass varies, length of string the same
Look over you data. Increasing the mass tightens the string
and increases its tension. Make a general statement (write a
sentence) about what happens to the pitch as you change
the tension on the string.
Physics Talk: Changing the Pitch
To produce sound, something must vibrate.
 You
 observed the vibration of the string as it produced
sound.
 investigated two of the variables, ___________ and
___________ that affect the pitch of the sound
Physics Talk
 Shortening the string (increased / decreased / didn’t
change) the pitch.

 When you added mass to the mass hanger on the end
of the string, you (increased / decreased / didn’t
change) the pitch.

 This is because increasing the mass (increases /
decreases / doesn’t change) the tension of the string.
Physics Talk
 Combining the two results, you can say that
(increasing / decreasing) the tension or
(increasing / decreasing) the length of the string
will increase the pitch.
Checking Up (p. 487)
1. What happens to the pitch of the sound produced by
a string when its tension is increased?
2. When you decrease the length of a string in an
instrument, how does the pitch of the sound you
hear change?
3. What effect did adding mass to the mass hanger have
on the string in the Investigate?
4. How is sound produced in a percussion instrument?
What Do You Think Now?
 How do guitarists or violinists today make different
sounds?
 If someone were pretending to play a guitar (for
example, the air guitar), how would the player position
his or her fingers to make the highest pitch notes?

You investigated the effects of changing the length of the
string and the tension of the string have on the pitch
of the sound produced.
How do you now think that these musicians make
sounds with different pitches? Use evidence from your
Essential Questions (p.489)
Complete in your science notebooks, then we’ll discuss
as a class.
 What does it mean?
A violin is less than 0.5 m long. A bass fiddle is more
than 1.5 m long. Which instrument do you expect to be
able to play notes with a lower pitch and why?
 How do you know?
What experiment can be conducted to demonstrate
that higher pitch sounds can be produced by either
shortening the length of a vibrating string or by
increasing the tension of a vibrating string?
Essential Questions (p.489)
Complete in your science notebooks, then we’ll discuss
as a class.
 Why do you believe?
How might the length of the string and the tension of
the string relate to the properties of the wooden bars
in these instruments?
 Why should you care?
List some examples where vibrating strings show up in
musical instruments. Describe how a drum produces
sound. How will what you learned in this section help
you with your challenge of creating sound?
What do you think?
 How does water move to make a wave?
Investigate
complete sentences
 1a)
 1b)
 1c)
 1d)
Divide and Conquer
Three roles:
 Director – responsible for having the textbook,
reading it aloud, and giving instructions to the other
group members.
 Recorder – responsible for writing everything in the
science notebook and sharing results with the group at
a later time.
 Worker – responsible for doing what the director tells
them and telling the recorder what to record.
Investigate
PART B: Producing Transverse Waves on a Spring (1-8)

 1a)                                        5a)
 2a)                                        TABLE 6a-b, 7 a-c
 2b)                                        7d)
 2c)                                        Skip 9
 2d)
 2e)
 3a)
Investigate
Periodic Waves (B: 10-15)
 10a)
 11a)
 11b)
 12a)
 TABLE 13a-b
 SKIP 14
 15a-c)
Investigate
PART C: Producing Longitudinal (Compressional)
Waves on a Spring
complete sentences
 1. Show calculation of the speed of compressional wave
 TABLE 1a)
 1b)
 1c)
 1d)
Investigate
PART D: Using a Wave Viewer
complete sentences
 4a)
Physics Talk
 Waves Transfer Energy
Copy the following sentences in your science notebook.
_________
1. A __________ is a transfer of energy with no net
wave
transfer of mass.
2. The energy moving along the spring came from
arms
chemical energy stored in your _______.
3. Energy is always ____________ .
conserved
medium
4. The coiled spring is the _____________ through
which the wave travels and through which energy is
transferred.
Physics Talk
5. For water waves, the medium is __________________.
the surface of water
6. As waves pass each other, they ______ as they pass.
travel
Then they continue to ________ as if the other wave
Physics Talk
 Vocabulary
Write the definitions to the following in your science
notebooks.
1. periodic wave
2. crest                      8. transverse wave
3. trough                     9. compressional wave
4. amplitude                  10. standing wave
5. wavelength                 11. node
6. frequency                  12. antinode
7. period
Physics Talk
 Draw and label a diagram showing the parts of a wave.
Include
 wavelength
 amplitude
 crest
 trough
Physics Talk
 Draw and label the parts of a standing wave with three
antinodes and four nodes. Label the nodes and
antinodes, as well as the wavelength.
Physics Talk
 For the sound wave below, label compressions and
rarefactions. Also, graph the compressions as crests
and rarefactions as troughs of the wave.
Physics Talk
 ( Compressional / Transverse ) waves on a coiled
spring are similar to sound waves in air.
 Sound is transferred through air by ______________ it
and __________________ it.
 The speed of a wave is found by the following formula
speed = distance traveled / time elapsed
 In symbols,
v = d/ t
Interference
 When two waves travel through the same space,
INTERFERENCE occurs.
 The AMPLITUDE of the wave may be determined
from the SUPERPOSITION of the individual
amplitudes.
Types of Interference
 If the amplitudes are in the SAME direction
(aligned), the amplitudes are added and the
interference is said to be CONSTRUCTIVE.

 If the amplitudes are in OPPOSITE directions, the
amplitudes are subtracted and the interference is
said to be DESTRUCTIVE.
Constructive Interference
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Constructive Interference
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The amplitude of the superposition is
GREATER than that of the two original
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Destructive Interference
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Destructive Interference
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The amplitude of this wave is LESS
than that of the two original waves
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Destructive Interference
 If the amplitudes of the waves are equal in magnitude
and out of phase by half a wavelength (/2),
perfect destructive interference occurs.
Destructive Interference
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/2

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
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Destructive Interference
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superposition is
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Demonstration with
Sound Waves
 Constructive and destructive interference with stereo
sound.
Wave Pulses
 Wave pulses pass through one another, interfering
constructively or destructively during the time they
occupy the same space.

 Demonstration with slinkys or ropes.
Wave Pulses
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Wave Pulses
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Wave Pulses
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Wave Pulses
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Wave Pulses
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Wave Pulses
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