Md.3ca..Physics..Sound

Turn in your answers to the following problems below. As always, make sure to show all of your work. 1. Sound waves travel through an aluminum bar at a speed of 1400 m/s. If the frequency of the sound wave is 1000 Hz, what is the distance between crests on a sound wave traveling through aluminum? 2. An airplane flies horizontally at a constant speed, piloted by rescuers who are searching for a disabled boat. When the plane is directly above the boat, the boat's crew blows a loud horn. By the time plane's sound detector receives the horn's sound, the plane has traveled a distance equal to one-half its altitude above the ocean. (The speed of sound is 343 m/s.) If it takes the sound 4.00s to reach the plane, determine a) the altitude of the plane, and b) its speed, in m/s. What is its speed in knots (nautical miles per hour)? 3. (Rev 9/11) Estimate the wavelength of a 20,000 Hz sound wave, which is near the upper limit of audibility for humans. Assume air at standard temperature and pressure. 4)(9/11) An organ pipe is a closed-ended air column. If its bottom note has a frequency of 20 Hz (close to the lowest audible frequency), then how long is the column? Assume standard temperature and pressure. 5. (Rev 2/11) The sound of a truck horn, observed when the truck is stationary, is 440 Hz. A drunk is sitting in the middle of the road at night. He sees the truck's headlights, and hears a 480 Hz horn. How rapidly is the truck approaching him, in m/s2? In mph? (As before, assume the speed of sound in air is 343 m/s.)