Additional Problems

| 81 | The bellow of a territorial bull hippopotamus has been measured at 115 dB above the threshold of hearing. What is the sound intensity?

| 82 | For research purposes a sonic buoy is tethered to the ocean floor and emits an infrasonic pulse of sound. The period of this sound is 71 ms. Determine the wavelength of the sound.

| 83 | ssm At 20 °C the densities of fresh water and ethyl alcohol are, respectively, 998 and 789 kg/m3. Find the ratio of the adiabatic bulk modulus of fresh water to the adiabatic bulk modulus of ethyl alcohol at 20 °C.

| 84 | A bird is flying directly toward a stationary bird-watcher and emits a frequency of 1250 Hz. The bird-watcher, however, hears a frequency of 1290 Hz. What is the speed of the bird, expressed as a percentage of the speed of sound?

| 85 | ssm Suppose the linear density of the A string on a violin is . A wave on the string has a frequency of 440 Hz and a wavelength of 65 cm. What is the tension in the string?

| 86 | Consider the freight train in Figure 16-6. Suppose 15 boxcars pass by in a time of 12.0 s and each has a length of 14.0 m. (a) What is the frequency at which each boxcar passes? (b) What is the speed of the train?

| 87 | ssm Humans can detect a difference in sound intensity levels as small as 1.0 dB. What is the ratio of the sound intensities?

| 88 | The average sound intensity inside a busy neighborhood restaurant is . How much energy goes into each ear during a one-hour meal?

| 89 | ssm Suppose the amplitude and frequency of the transverse wave in Figure 16-2c are, respectively, 1.3 cm and 5.0 Hz. Find the total vertical distance (in cm) through which the colored dot moves in 3.0 s.

| 90 | Refer to the graphs that accompany problem 24. From the data in these graphs, determine the speed of the wave.

| 91 | ssm A speeder looks in his rearview mirror. He notices that a police car has pulled behind him and is matching his speed of 38 m/s. The siren on the police car has a frequency of 860 Hz when the police car and the listener are stationary. The speed of sound is 343 m/s. What frequency does the speeder hear when the siren is turned on in the moving police car?

| 92 | Consult Interactive LearningWare 16.1 at for insight into this problem. At what temperature is the speed of sound in helium (ideal gas, , ) the same as its speed in oxygen at 0 °C?

| 93 | ssm A listener doubles his distance from a source that emits sound uniformly in all directions. By how many decibels does the sound intensity level change?

| 94 | A rocket engine emits of sound energy every second. The sound is emitted uniformly in all directions. What is the sound intensity level, measured relative to the threshold of hearing, at a distance of 85 m away from the engine?

* | 95 | In a discussion person A is talking 1.5 dB louder than person B, and person C is talking 2.7 dB louder than person A. What is the ratio of the sound intensity of person C to the sound intensity of person B?

Problem 96

* | 96 | A 3.49-rad/s ( rpm) record has a 5.00-kHz tone cut in the groove. If the groove is located 0.100 m from the center of the record (see drawing), what is the wavelength in the groove?

* | 97 | ssm www The drawing shows a frictionless incline and pulley. The two blocks are connected by a wire (mass per unit length = 0.0250 kg/m) and remain stationary. A transverse wave on the wire has a speed of 75.0 m/s. Neglecting the weight of the wire relative to the tension in the wire, find the masses m1 and m2 of the blocks.

* | 98 | Review Conceptual Example 3 before starting this problem. The amplitude of a transverse wave on a string is 4.5 cm. The ratio of the maximum particle speed to the speed of the wave is 3.1. What is the wavelength (in cm) of the wave?

* | 99 | Review Conceptual Example 3 before starting this problem. A horizontal wire is under a tension of 315 N and has a mass per unit length of . A transverse wave with an amplitude of 2.50 mm and a frequency of 585 Hz is traveling on this wire. As the wave passes, a particle of the wire moves up and down in simple harmonic motion. Obtain (a) the speed of the wave and (b) the maximum speed with which the particle moves up and down.

* | 100 | When one person shouts at a football game, the sound intensity level at the center of the field is 60.0 dB. When all the people shout together, the intensity level increases to 109 dB. Assuming that each person generates the same sound intensity at the center of the field, how many people are at the game?

** | 101 | A jet is flying horizontally, as the drawing shows. When the plane is directly overhead at B, a person on the ground hears the sound coming from A in the drawing. The average temperature of the air is 20 °C. If the speed of the plane at A is 164 m/s, what is its speed at B, assuming that it has a constant acceleration?

** | 102 | The sonar unit on a boat is designed to measure the depth of fresh water (, ). When the boat moves into seawater (, ), the sonar unit is no longer calibrated properly. In seawater, the sonar unit indicates the water depth to be 10.0 m. What is the actual depth of the water?

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