Question

1. The speed of sound in an alcohol at a temperature of 20°C is 1260 m/s. The density of the alcohol at that temperature is 650 kg/m^3. At a temperature of 20°C, find the bulk modulus of the alcohol.

• 1030 MPa
• 1080 MPa
• 1140 MPa
• 1190 MPa
• 1240 MPa

2. During a thunderstorm, you hear the sound 4 s after you see the lightning flash. How far did it fall? Assume the temperature outside is approximately 20

• 1.324 km
• 1.372 km
• 1.360 km
• 1.348 km

3. A certain source of sound waves radiates uniformly in all directions. At a distance of 20 m from the source the intensity level is 51 db. What is that intensity in W/m^2?

• 1.26 x 10^{-6}
• 1.26 x 10^{-7}
• 1.26 x 10^{-8}
• 1.26 x 10^{-9}

4. A certain source of sound waves radiates uniformly in all directions. At a distance of 20 m from the source the intensity level is 51 db. What is the total acoustic power output of the source, in watts?

• 5.04 x 10^{-5} W
• 1.58 x 10^{-4} W
• 6.33 x 10^{-4} W
• 1.28 x 10^{-3} W

5. The sound level at 1.0 m from a certain talking person talking is 60 dB. You are surrounded by 10 such people, all 1.0 m from you and all talking equally loud at the same time. What sound level are you being exposed to? You can neglect any absorption, reflection, or interference of the sound.

• 600 dB
• 60 dB
• 70 dB
• 100 dB

6. You can vary the length of an air column, open at one end and closed at the other. You strike a tuning fork that vibrates at 512 Hz. Which of the following lengths of the air column will not allow for a standing wave pattern to occur? Sound in air is 340 m/s?

• 83.0 cm
• 33.2 cm
• 16.6 cm
• 49.8 cm

7. The sound from a single source can reach point O by two different paths. The first destructive interference occurs when one path is 20.0 m long and the second path is 21.0 m long. What is the wavelength. Speed of sound is 340 m/s.

• 17 m
• m
• m
• 8.0 m

8. A person is hearing two sound waves simultaneously. One has a period of 1.50 ms and the other one a period of 1.54 ms. What is the period of the beat due to these two waves?

• 0.040 ms
• 1.5 ms
• 3.0 ms
• 58 ms
• 330 ms

9. As you stand by the side of the road, a car approaches you at a constant speed, sounding its horn, and you hear a frequency of 80.0 Hz. After the car goes by, you hear a frequency of 60.0 Hz. What is the speed of the car? The speed of sound in the air is 343 m/s.

• 64.0 m/s
• 49.0 m/s
• 16.0 m/s
• 36.0 m/s
• 25.0 m/s

Answer 1

1) Speed of sound = sqrt(Bulk modulus/density)

Bulk modulus = (1260)^2 * 650 * 10^-6 MPa

= 1032 MPa

1030 MPa is the correct option.