1. Determine the speed of sound when the air temperature is
a) -10o C b) 24o C c) 35o C
2. The air temperature is 20o C when a bolt of lightning occurs. It takes 10.0 s for the thunder
to be heard. Calculate the distance to where the lightning occurred.
3. The school rings its bell at noon every day. A person 4.8 km away sets her watch by this bell.
Given the air temperature is 20o C, how slow will her watch be?
4. The speed of sound in water is 1.4 X 103 m/s, and the speed in air is 340 m/s. A bird dives
into the water to catch a fish. How far away did the bird enter the water if the sound of the
splash takes 1.0s longer in reaching the observer when it travels through the air than when it
travels through the water?
5. The air temperature is 12o C when a plane flies overhead. Determine the Mach number of the
plane if its speed is
a) 1020 m/s b) 170 m/s c) 1836 km/h
6. A new experimental airplane can fly at Mach 2.0. If the air temperature is 0o C, what is the
speed of the plane in kilometers per hour?
7. Determine the speed of a sound from a vibrating string if the frequency is 260 Hz and the
wavelength is 1.30 m.
8. Calculate the frequency of a sound wave with a speed of 350 m/s and a wavelength of 10 m.
9. A tuning fork produces a sound with frequency 440 Hz. The temperature in the room is
20o C, and an observer is 40 m away. How many vibrations of the tuning fork occurred before
the observer hears the sound?
10. The roar of a lion releases sound with a power of 1 X 10-6W. If it were possible to convert
all of the sound energy into electrical energy, how many roaring lions would be needed to keep
a 60 W light bulb lit?
11. The area of the average eardrum is 4.0 X 10-5 m2. For an 80 dB sound, determine the
amount of energy falling on the eardrum per second.
12. Sonar is used to determine the depth of a lake. The interval of time between sending the signal
out and the return signal is 0.40 s. Find the depth of the water if the sound travels at 1500 m/s
in the water.
13. On a cool foggy night, a ship sounds its fog horn. The echo is heard 11.0 s later. Given the
air temperature is 10o C, determine the distance to the object that reflected the sound.
14. A destroyer receives its sonar signal back in 4.5 s after being reflected off of a submarine. If
the speed of sound in the water is 1.47 X 103 m, how far away is the submarine?
November 22, 2013