KEY Guided Notes Waves: Period, Frequency, and Velocity
June 15th 2015
Catalyst/Prompt •
What is a mechanical wave? o A wave that carries energy from one place to another & requires a medium
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What are the three types & what are their physical properties? o Transverse: Energy travels perpendicular to motion of medium; has a crest & trough o Longitudinal/compressional: Energy travels parallel to medium; has compressions & rarefactions o Surface: Separates two media & moves in a circular motion The time required for one cycle, a complete motion that returns to its starting point, is called the period Any periodic motion has frequency, which is the number of complete cycles in a given time Frequency is measured in hertz(Hz) Frequency depends on energy o The more energy, the higher the frequency o The less energy, the lower the frequency Amplitude & energy are directly proportional o The more energy, the greater the amplitude Frequency & wavelength are inversely proportional o When frequency increases, wavelength decreases o When frequency decreases, wavelength increases
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Wave frequency x wavelength = wave speed Formula: wave speed = frequency x wavelength
Practice Problems
1. One end of a rope is vibrated to produce a wave with a wavelength of 0.25 meters. The frequency of the wave is 3.0 hertz. What is the speed of the wave? a. Formula? Wave speed = wavelength x frequency b. Plug in the #s: Wave speed = 0.25 x 3.0 = 0.75 m/s
2. A wave on a rope has a wavelength of 2.0m and a frequency of 2.0Hz. What is the speed of the wave? a. Formula? Wave speed = wavelength x frequency b. Plug in the #s: Wave speed = 2.0 x 2.0 = 4.0m/s
3. A motorboat is tied to a dock with its motor running. The spinning propeller makes a surface wave in the water with a frequency of 4 Hz and a wavelength of 0.1m. What is the speed of the wave? Answer: 0.4 m/s
4. What is the wavelength of an earthquake wave if it has a speed of 5 km/s and a frequency of 10 Hz? Answer: 0.5 km
5. A tuning fork has a frequency of 280 Hz and the wavelength of the sound produced is 1.5m. Calculate its velocity. Answer: 420 m/s
6. A wave is moving towards shore with a velocity of 5m/s. If its frequency is 2.5Hz, what is its wavelength? Answer: 2 m
7. A jump rope is shaken producing a wave with a wavelength of 0.5m a frequency of 4Hz. What is its speed? Answer: 2 m/s
8. A p-‐wave travels at 30m/s along the Earth’s crust. If it has a frequency of 10Hz, what is its wavelength? Answer: 3 m
9. A compressional wave travels down a slinky going 12m/s. If it has a wavelength of 2m, what is its frequency? Answer: 6 Hz
10. A surfer rides a wave with a frequency of 5 Hz going 25 m/s. What is the wave’s wavelength? Answer: 5 m