solved problem mechanical wave
Answers
Answer:
1.On the surface of the lake floats two pieces of wood, the distance between them is 6 m. The waves propagate on the surface of the lake. When the first wood has moved up and down three times, the second wood just moved up and down one time. If every 2 seconds both kinds of wood move up and down three times, the wave propagation is …
A. 4.5 m/s
B. 3.0 m/s
C. 2.0 m/s
D. 1.5 m/s
Known :
Distance between both woods (l) = 6 meters
The first timber has moved up and down three times; the second wood just moved up and down one time.
Frequency (f) = 3 / 2 = 1.5 hertz
Wanted: Speed of wave (v)
Solution :
When the first wood moves up and down one time, the wavelength 1 travels to the second wood. When the first wood moves up and down two times, the wavelength 2 travels to the second wood. When the first wood moves up and down three times, the wavelength one has arrived at the second wood position so that at the same time the second wood moves up and down one time.
Thus, the distance between the first wood and the second wood is two wavelengths (2 λ), as shown in the picture on the side.
Distance of 1 wavelength (λ) = 6 / 2 = 3 meters
The speed of the wave propagation (v):
v = f λ = (1.5 hertz)(3 meters)
v = 4.5 m/s
The correct answer is A.
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