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Unformatted text preview: Chapter 17 Problems 1, 2 , 3 = straightforward, intermediate, challenging Section 17.1 Speed of Sound Waves 1 . Suppose that you hear a clap of thunder 16.2 s after seeing the associated lightning stroke. The speed of sound waves in air is 343 m/s and the speed of light in air is 3.00 10 8 m/s. How far are you from the lightning stroke? 2. Find the speed of sound in mercury, which has a bulk modulus of approximately 2.80 10 10 N/m 2 and a density of 13 600 kg/m 3 . 3. A flowerpot is knocked off a balcony 20.0 m above the sidewalk and falls toward an unsuspecting 1.75-m-tall man who is standing below. How close to the sidewalk can the flower pot fall before it is too late for a warning shouted from the balcony to reach the man in time? Assume that the man below requires 0.300 s to respond to the warning. 4. The speed of sound in air (in m/s) depends on temperature according to the approximate expression v = 331.5 + 0.607 T C where T C is the Celsius temperature. In dry air the temperature decreases about 1C for every 150 m rise in altitude. (a) Assuming this change is constant up to an altitude of 9 000 m, how long will it take the sound from an airplane flying at 9 000 m to reach the ground on a day when the ground temperature is 30C? (b) What If? Compare this to the time interval required if the air were a constant 30C. Which time interval is longer? 5. A cowboy stands on horizontal ground between two parallel vertical cliffs. He is not midway between the cliffs. He fires a shot, and hears its echoes. The second echo arrives 1.92 s after the first, and 1.47 s before the third. Consider only the sound traveling parallel to the ground and reflecting from the cliffs. Take the speed of sound as 340 m/s. (a) What is the distance between the cliffs? (b) What If? If he can hear a fourth echo, how long after the third echo does it arrive? 6. A rescue plane flies horizontally at a constant speed searching for a disabled boat. When the plane is directly above the boat, the boat's crew blows a loud horn. By the time the planes sound detector perceives the horns sound, the plane has traveled a distance equal to one-half its altitude above the ocean. If it takes the sound 2.00 s to reach the plane, determine (a) the speed of the plane, and (b) its altitude. Take the speed of sound to be 343 m/s....
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