91Ó°ÊÓ

Question: Figure 17-30 shows a stretched string of lengthand pipes a,b, c, and dof lengthsL, 2L, L/2, andL/2, respectively. The string’s tension is adjusted until the speed of waves on the string equals the speed of sound waves in the air.Thefundamental mode of oscillationis then set up on the string. In which pipe will the sound produced by the string cause resonance, and what oscillation mode willthat sound set up?

Question: A friend rides, in turn, the rims of three fast merry-go-roundswhile holding a sound source that emits isotropically at a certain frequency. You stand far from each merry-go-round. The frequency you hear for each of your friend’s three rides varies as the merry-go-round rotates. The variations in frequency for the three rides aregiven by the three curves in Fig. 17-29. Rank the curves according to:

(a) the linear speed vof the sound source, (b) the angular speedsvofthe merry-go-rounds, and (c) the radii rof the merry-go-rounds, greatest first

Question: A source S and a detector D of radio waves are a distancedapart on level ground (Fig. 17-52). Radio waves of wavelength $\mathrm{λ}$reach D either along a straight path or by reflecting (bouncing) from a certain layer in the atmosphere. When the layer is at heightH, the two waves reaching D are exactly in phase. If the layer graduallyrises, the phase difference between the two waves gradually shifts, until they are exactly out of phase when the layer is at height H +h. Express $\mathrm{λ}$in terms of d, h, and H.

Question: A listener at rest (with respect to the air and the ground) hears a signal of frequency $f_1$from a source moving toward him with a velocity of 15 m / s, due east. If the listener then moves toward the approaching source with a velocity of$25\frac{m}{s}$, due west, he hears a frequency$f_2$that differs from$f_1$by 37 Hz. What is the frequency of the source? (Take the speed of sound in air to be$340\frac{m}{s}$).

Question: Diagnostic ultrasound of frequency is 4.50 MHz used to examine tumors in soft tissue. (a) What is the wavelength in air of such a sound wave? (b) If the speed of sound in tissue is , what is the wavelength of this wave in tissue?

Question: You are given four tuning forks. The fork with the lowest frequency oscillates at 500 Hz. By striking two tuning forks at a time,you can produce the following beat frequencies, 1, 2, 3, 5, 7, and 8Hz. What are the possible frequencies of the other three forks?(There are two sets of answers)

Question: The pressure in a traveling sound wave is given by the equation

.$\mathit{Δ}\mathbf{p}\mathbf{=}\left(1.50Pa\right)\mathit{s}\mathit{i}\mathit{n}\mathit{π}\left[\left(1.900m^{-1}\right)x-\left(1315s^{-1}\right)t\right]$

Find the (a) Pressure amplitude, (b) Frequency, (c) Wavelength, and (d) Speed of the wave

Question: A sound wave of the form $\mathbf{s}\mathbf{=}{\mathbf{s}}_{\mathbf{m}}\mathit{c}\mathit{o}\mathit{s}\left(\mathrm{kx}-\mathrm{Ó\neg ³Ù}+f\right)$travels at 343 m/s through air in a long horizontal tube. At one constant, air molecule Aat x =2.00m is at its maximum positive displacement of 6Nm and air molecule B at x =2.070 m is at a positive displacement of 2N/m . All the molecule between A and B are at intermediate displacement. What is the frequency of the wave?

Question: A handclap on stage in an amphitheater sends out sound waves that scatters from terraces of width W 0.75 mfigure. The sound returns to the stage as a periodic series of pulses, one from each terrace; the parade of pulses sounds like a played note (a)Assuming that all the rays in figure are horizontal , find the frequency at which the pulses return(that is ,the frequency of the perceived note .(b)If the widthof the terraces were smaller would the frequency be higher or lower?

Question: Two sound waves, from two different sources with the same frequency,540 Hz,travel in the same direction at330 m/s. The sources are in phase. What is the phase difference of the wave at a point that is 4.40 mfrom one sound andfrom the other?