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Homework Help: Sound to travel form the TV to the viewer

  1. Oct 17, 2008 #1
    1. The problem statement, all variables and given/known data
    A celebrity holds a press conference, which is televised live. A television viewer hears the sound picked up by a microphone directly in front of the celebrity. This viewer is seated 2.9 m from the television set. A reporter at the press conference is located 5.2 m from the microphone and hears the words directly at the very same instant that the television viewer hears them. Using a value of 343 m/s for the speed of sound, determine the maximum distance between the television viewer and the celebrity.

    2. Relevant equations
    Let the time required for the sound to travel form the TV to the viewer be t1 = d1/v, where the symbols have their usual meaning. Let the time required for the sound to travel from the celebrity to the reporter be t2 = s2/v . The time required for the EM wave to travel to the viewer's set is t = s/c . Using the information given in the problem statement, construct a relationship between these three times.

    3. The attempt at a solution
    t1 = 8.45e-3 sec
    t2 = 1.50e-2 sec
    so should t = t1 + t2
    then t1 + t2 = s/ 3.00e8 then just solve for s , i did solve for s this way but its wrong
  2. jcsd
  3. Oct 17, 2008 #2


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    Homework Helper

    Why have you added the times together?

    Isn't the difference what you're interested in?
  4. Oct 17, 2008 #3
    even adding or subtracting , its still the wrong asnwer
  5. Oct 17, 2008 #4


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    Homework Helper

    There is no adding to get to the right answer.

    Isn't time * velocity the distance though?
  6. Nov 17, 2008 #5
    You have to divide the distances / speed of sound to get the two times, subtract, then multiply by speed of light.
    remember: the reporter hears the sound at the exact same time as the viewer. you have to adjust the equation for the time that it takes both individuals to hear the sound and then adjust for the viewer who is "seeing" it.

    d1/343 = t1

    d2/343 = t2

    (t1-t2) x 3e8

    ----exact same problem on hw....got it right.
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