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Agenda Logistics: Syllabus and Web Page Clicker Setup Course Overview--the models of 7C Simple Harmonic Motion Review Wave Introduction
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Course webpage http://physics.ucdavis.edu/physics7
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Clicker Setup: Joining Class
1) Turn on your clicker; it scans for classes2) If it doesn’t scan automatically, hit enter
(green button)3) Find 09SS1PHY7C; hit enter4) Display reads “ANS: 09SS1PHY7C;” hit
enter5) When you’ve successfully joined, display
reads “ANS: wait for Q”
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Clicker Setup: Student ID
1) Turn on your clicker
2) Press * to access Setup Menu
3) Scroll to find “ID;” hit Enter (green button)
4) Enter your Student ID so I can give you credit; hit enter
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Check Clicker Setup
When did you take 7B?
a) Spring 09
b) Winter 09
c) Fall 09 or earlier
d) Didn’t take 7B (but took 7A)
e) I haven’t taken any 7-series classes
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Course Overview:Models of 7C Wave Model
Waves in 1, 2, and 3 dimensions Interference
Ray Model Reflection & Refraction Lenses
Field Model Electricity Magnetism
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Simple Harmonic Motion Review
How can we describe the motion of oscillating objects?
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Simple Harmonic Motion (SHM) Constructs Amplitude: maximum distance from equilibrium Period (or frequency): amount of time required to
complete a cycle (or number of cycles per unit time) Equilibrium: position at which all forces acting on the
object sum to zero. Displacement: position of the object relative to
equilibrium Restoring Force: a force that acts on an object that
tends move it toward equilibrium Defining SHM: The restoring force is proportional to the
displacement. Anything missing? xF k x=−
uur r
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Mathematics of SHMy=Displacement
A=Amplitude
T=Period
t
y
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Mathematics of SHMy=Displacement
A=Amplitude
T=Period
t
y
In this image, which numbers, if any, show… Displacement?
1
4
3
5
2
6
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Mathematics of SHMy=Displacement
A=Amplitude
T=Period
t
y
In this image, which numbers, if any, show…
1
4
3
5
2
6
Amplitude?
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Mathematics of SHMy=Displacement
A=Amplitude
T=Period
t
y
In this image, which numbers, if any, show…
1
4
3
5
2
6
Period?
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Mathematics of SHM
y=Displacement
A=Amplitude
T=Period
t
y
y(t) = A sin (2 t/T)???
In this image, what is the mass doing at t=0 seconds?
A
T
T
A
Is the equation correct as is?
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Mathematics of SHM
y=Displacement
A=Amplitude
T=Period
t
y
y(t) = A sin (2 t/T + )
In this image, what is the mass doing at t=0 seconds?
In this image, what value does
have?
T
=phase
y(t) = A sin (2 t/T)?
A
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Introduction to Waves
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
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Questions to consider about waves…
What new constructs are needed to describe waves?
What constructs can I control when I start the wave?
What constructs are set by the medium that carries the wave?
What moves from one end of the machine to the other?
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
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Definition of Wave Waves: A transfer of energy without
bringing along the mass. Particles in the medium get disturbed and
collide, but they stay oscillating about one position; they don’t travel with the wave.
The medium does not effectively move. The disturbance advances, that’s the wave.
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A vibrating object acts as the source of the wave. As a speaker moves through a cycle, it fixes the period and frequency.
t xy(x, t) A sin ( 2 2 )
T
λ= + +
A = Amplitude, controlled by what starts the waveT = Period, how long to get back to where it started = Wavelength, repeat distance in space
T = where f is the frequency
Velocity v = f (note meters per second)
f
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