Transcript Force and Motion - University of South Florida

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Force and Motion
Ophir Ortiz and Souheil Zekri
Standard 1:
2. knows that waves travel at
different speeds through different
materials
Why are waves important?
• Waves are
• Waves transmit energy
that topple buildings
during earthquakes
Figure 1: Seismogram
•
Figure 2: Satellite
Our observations from
earth to space are
dependent on waves
received by satellites
Outline
•
•
•
•
Definition of a wave
Characteristics of waves
Examples of waves
Activity
What is a wave?
• Definition: A disturbance traveling through
a medium by which energy is transferred
from one particle of the medium to
another without causing any permanent
displacement of the medium itself
• In simpler terms, a wave may be
described as a ripple or an undulation
Stadium wave
http://www.colorado.edu/physics/2000/waves_particles/stadium_wave.html
Characteristics of Waves
• The characteristics of a waveform are:
• wavelength (period)
• amplitude
• velocity
• frequency
• All periodic (repeating) waveforms have
these common characteristics
Wavelength
• Wavelength is defined as
the distance from one crest
to the next crest.
• The wavelength of an ocean wave:
several meters.
• The wavelength of the electromagnetic wave used in
a microwave oven:
~ 1 centimeter.
Wavelength Applet
Amplitude
Amplitude
A
• The height of the wave is called its amplitude.
• Amplitude relates to loudness in sound (for a sound
wave) and brightness in light (for an
electromagnetic wave).
Velocity
• The velocity of the wave is the measurement of
how fast a crest is moving from a fixed point.
• The speed of sound is about 1000 feet/second.
• The speed of light is
2.99 x 108 meters/second.
Frequency
• The frequency of waves is the rate the crests
or peaks pass a given point. Cycles per second
is also called Hertz.
Frequency = Velocity / Wavelength
Classification of Waves
Mechanical
Electromagnetic
Classification
according to medium
through which wave
travels
Longitudinal
Transverse
Torsional
Classification
according to wave
orientation
Mechanical Waves
• Matter is the
medium
• Sound is a
mechanical wave
Electromagnetic Waves
• Electric and magnetic fields are the
media
• Light is an electromagnetic wave
Longitudinal Waves
• A sound wave is a classic example of a longitudinal
•
wave
As a sound wave moves from the lips of a speaker
to the ear of a listener, particles of air vibrate back
and forth in the same direction and the opposite
direction of energy transport
http://www.glenbrook.k12.il.us/gbssci/phys/Class/sound/u11l1a.html
Transverse Waves
• Disturbance is perpendicular to the direction of
propagation
Perpendicular: Two lines
that meet at a right (90°)
angle
• All electromagnetic waves are transverse. This
includes light.
Transverse Waves
• Particles vibrate at right angles to the direction
of the wave's velocity
Example: waves along a string
PARTICLE
DISPLACEMENT
90°
VELOCITY
http://online.cctt.org/physicslab/content/Phy1/lessonnotes/waves/lessonwaves.asp
Torsional Waves
• waves which twist about a central axis
Tacoma Bridge
Sound Waves
• Sound is a waveform that
travels through matter
• Sound will readily travel
through many materials
• Speed of sound through
air depends on:
– density of the material
– temperature
Material
Air
Velocity
m/s
331
Water
(50°C)
Brass
1540
Aluminum
6400
4490