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Some Logistics
Course Webpage: http://physics.ucdavis.edu/physics7
Simple Harmonic Oscillation Review
How can we describe the motion of oscillating objects?
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
Mathematics of SHM
y=Displacement
A=Amplitude
T=Period
t
y
In this image, which numbers, if any, show… Displacement?
1
4
3
5
2
6
Amplitude?
Period?
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?
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
Making Waves
Watch waves How does the motion you are
watching differ from the motion of the mass-spring?
How is it the same? What new constructs are
needed to describe waves? What constructs can I control
when I start the wave? What moves from one end of the
machine to the other?
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
Wave Constructs
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.
Graphing Wavesa) At a particular time (holding position constant)
b) At a particular position (holding time constant)
Mathematics of Harmonic Waves
Displacement (y) is a function of both position along the medium and time. y(x,t)
In space, function repeats every wavelength In time, function repeats every period
t xy(x, t) A sin ( 2 2 )
T
λ= + +
Longitudinal vs. Transverse Wave Polarization
Longitudinal Wave Transverse Wave
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