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Unformatted text preview: homework 22 – RAHMAN, TARIQUE – Due: Apr 25 2008, 3:00 am 1 Question 1, chap 16, sect 2. part 1 of 1 10 points Which requires a physical medium in which to travel? 1. sound correct 2. light 3. neither sound nor light 4. both sound and light Explanation: Sound requires a physical medium in which to travel. Light does not. Question 2, chap 16, sect 2. part 1 of 1 10 points A harmonic longitudinal wave propagating down a tube filled with a compressible gas has the form s ( x, t ) = s m cos( kx ωt ) . Its velocity can be obtained from 1. ω 2. ωk 3. k 4. ω/k correct 5. k/ω Explanation: For a wave described by A ( x, t ) = A m sin( k x ω t ) or A ( x, t ) = A m cos( kx ωt ) , its velocity is ω/k. Question 3, chap 16, sect 3. part 1 of 1 10 points The figure shows two wave pulses that are approaching each other. P Q Which of the following best shows the shape of the resultant pulse when the centers of the pulses, points P and Q , coincide? 1. 2. 3. 4. correct 5. Explanation: Notice that the two pulses have the same width and amplitude. Choosing the point P (the same as point Q when the two pulses coincide) as the origin, the two pulses can be described as: P : y 1 = A , d ≤ x ≤ d Q : y 2 = braceleftBigg A , d ≤ x < A , < x < d homework 22 – RAHMAN, TARIQUE – Due: Apr 25 2008, 3:00 am 2 Using the principle of superposition, the re sultant pulse is y = y 1 + y 2 = braceleftbigg 2 A , d ≤ x < , < x < d bracerightbigg . P Q P + Q Question 4, chap 16, sect 3. part 1 of 1 10 points Two similar tuning forks produce sound waves of the same 7 . 1 mPa amplitude. One tuning fork y 1 has a frequency 1386 s 1 and the other y 2 has a frequency of 1540 s 1 . These two tuning forks produce interference. + A + A AA T beat T wave y 1 y 2 y 1 + y 2 + A A 3 T beat 6 T beat What is the number of beats per second that is heard? Correct answer: 154 Hz (tolerance ± 1 %). Explanation: +14 14 A (mPa) t (milliseconds) 6 . 5 ms 13 ms y 1 y 2 y 1 + y 2 +14 14 A (mPa) t (milliseconds) 19 . 5 ms 39 ms Two harmonic waves are described by y 1 = A cos( k x ω 1 t ) and y 2 = A cos( k x ω 2 t ) , where A = 7 . 1 mPa , f 1 = 1386 s 1 , f 2 = 1540 s 1 , f 2 f 1 2 = 77 s 1 , f 1 + f 2 2 = 1463 s 1 , T wave = 1 f 2 f 1 2 = 13 ms , ω 1 = 8708 . 49 rad / s , ω 2 = 9676 . 11 rad / s , ω 2 ω 1 2 = 483 .....
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 Fall '08
 Turner
 Physics, Work, Light, Wavelength

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