It is possible to hear an approaching train before you can see it by listening to the sound wavethrough the track. If the elastic modulus is 2.0 x 1011 N/m2 and the density of steel is 7.8 x 103 kg/m 3,approximately how many times faster is the speed of sound in the track than in air? (Vair^ 340 m/s.)a. 20b. 5c. 10d. 15e. 25

The speed of the sound in steel is related to the Young’s modulus and the density of the steel.

Answered: It is possible to hear an approaching…

Physics for Scientists and Engineers: Foundations and Connections

1st Edition

ISBN:9781133939146

Author:Katz, Debora M.

Publisher:Katz, Debora M.

Chapter17: Traveling Waves

Section: Chapter Questions

Problem 65PQ

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Review. A 150-g glider moves at v1 = 2.30 m/s on an air track toward an originally stationary 200-g glider as shown in Figure P16.53. The gliders undergo a completely inelastic collision and latch together over a time interval of 7.00 ms. A student suggests roughly half the decrease in mechanical energy of the two-glider system is transferred to the environment by sound. Is this suggestion reasonable? To evaluate the idea, find the implied sound level at a position 0.800 m from the gliders. If the students idea is unreasonable, suggest a better idea. Figure P16 53
The bulk modulus of water is 2.2 109 Pa (Table 15.2). The density of water is 103 kg/m3 (Table 15.1). Find the speed of sound in water and compare your answer with the value given in Table 17.1.
When all the strings on a guitar (Fig. OQ13.5) are stretched to the same tension, will the speed of a wave along the most massive bass string be (a) faster, (b) slower, or (c) the same as the speed of a wave on the lighter strings? Alternatively, (d) is the speed on the bass string not necessarily any of these answers? Figure OQ13.5
Three metal rods are located relative to each other as shown in Figure P17.68. where Ls = L1 + L2. The speed of sound in a rod is given by = Y/p, where Y is Youngs modulus for the rod and is the density. Values of density and Young's modulus for the three materials are 1 = 2.70 X 103 kg/m3, Y1 = 7.00 1010 N/m, 2 = 11.3 103 kg/m3, = 1.60 1010 N/m2. s = 8.80 103 kg/m3 Ys = 11.0 1010N/m2. If L3 = 1.50m, what must the ratio L1/L2if a sound wave is to travel the length of rods 1 and 2 in the same time interval required for the wave to travel the length of rod 3?
When all the strings on a guitar (Fig. OQ16.5) are stretched to the same tension, will the speed of a wave along the most massive bass string be (a) faster, (b) slower, or (c) the same as the speed of a wave on the lighter strings? Alternatively, (d) is the speed on the bass string not necessarily any of these answers?
A skyrocket explodes 100 m above the ground (Fig. P14.24). Three observers are spaced 100 m apart, with the first (A) directly under the explosion. (a) What is the ratio of the sound intensity heard by observer A to that heard by observer B? (b) What is the ratio of the intensity heard by observer A to that heard by observer C? Figure P14.24
A sound wave in air has a pressure amplitude equal to 4.00 103 Pa. Calculate the displacement amplitude of the wave at a frequency of 10.0 kHz.
The area of a typical eardrum is about 5.00 X 10-5 m2. (a) (Calculate the average sound power incident on an eardrum at the threshold of pain, which corresponds to an intensity of 1.00 W/m2. (b) How much energy is transferred to the eardrum exposed to this sound lor 1.00 mill?
The tensile stress in a thick copper bar is 99.5% of its elastic breaking point of 13.0 1010 N/m2. If 500-Hz sound wave is transmitted through the material, (a) what displacement amplitude will cause the bar to break? (b) What is the maximum speed of the elements of copper at this moment? (c) What is the sound intensity in the bar?
A nylon guitar string is fixed between two lab posts 2.00 m apart. The string has a linear mass density of =7.20 g/m and is placed under a tension of 160.00 N. The string is placed next to a tube, open at both ends, of length L. The string is plucked and the tube resonates at the n=3 mode. The speed of sound is 343 m/s. What is the length of the tube?
As in Figure P18.16, a simple harmonic oscillator is attached to a rope of linear mass density 5.4 102 kg/m, creating a standing transverse wave. There is a 3.6-kg block hanging from the other end of the rope over a pulley. The oscillator has an angular frequency of 43.2 rad/s and an amplitude of 24.6 cm. a. What is the distance between adjacent nodes? b. If the angular frequency of the oscillator doubles, what happens to the distance between adjacent nodes? c. If the mass of the block is doubled instead, what happens to the distance between adjacent nodes? d. If the amplitude of the oscillator is doubled, what happens to the distance between adjacent nodes? FIGURE P18.16

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