Chapter 19. Vibrations and Waves . There are two ways to transmit information and energy in our universe:. Particle Motion and Wave Motion . Vibration -. Wiggle in time. Light and Sound Both are vibrations of different kinds. Wave -. Wiggle in space . 1. VIBRATION OF A PENDULUM.
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Vibrations and Waves
Wiggle in time
Light and Sound
Both are vibrations of
Wiggle in space
Demo - Metronome
Demo - Bowling ball pendulum
Video - Three Bowling Balls
Video - Swinging Examples
Demo - Pendulum with extra mass
Time to swing depends on the length but not the mass of the pendulum.
When the oscillation is small, the motion is called simple harmonic motion and can be described by a simple sine curve.
cycles per second
Hertz (Hz)2. WAVE DESCRIPTION
A - Amplitude
Distance a wave travels during one vibration
- meters or feetWavelength (l)
particles or waves.
Demo – Waves on a rope
A disturbance moves through the medium.
Elements of the medium vibrate.
(a) cuts it in half
(b) increases it by the square of 2
(d) doubles it
The average speed of anything is defined as
For a wave, if the distance traveled is a wavelength (l), then the time to travel this distance is the period (T ). Then
Demo - Complete Bell Wave Machine
Note: v is dictated by the medium.
(must change medium to change v)
f is dictated by the source.
(must change the source to change f )
Video - Slinky Longitudinal Waves
Rarefactions are regions of low density.
Compressions (condensations) are regions of high density.
l is the distance between successive rarefactions or successive compressions.
Example: sound in air
(c) source of the sound
(a) the frequency
(b) the wavelength
(c) the amplitude
(d) the period
(e) the medium of transmission
A skipper on a boat notices wave crests passing his anchor chain every 5 seconds. If the wave crests are 15 m apart, what is the speed of the water waves in m/s?
(c) density holes
Video - Superposition of Waves
Slide - Interference
There is maximum vibration at an antinode.
l is twice the distance between successive nodes or successive antinotes.
Refers to the change in frequency when there is relative motion between an observer of waves and the source of the waves
When a source of waves and an observer of waves are getting closer together, the observer of the waves observes a frequency for the waves that is higher than the emitted frequency.
When a source of waves and an observer of waves are getting farther apart, the observer of the waves observe a frequency for the waves that is lower than the emitted frequency.
(a) is greater than what the source emits
(b) is less than what the source emits
(c) is the same as what the source emits
(a) because the plane breaks through the sound barrier
(b) when the plane reaches the speed of sound
(c) by the plane traveling faster than the speed of sound
(d) by the plane traveling slower than the speed of sound