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Homework Help: Speed of EM waves in a baseball park setting

  1. Mar 6, 2012 #1
    1. The problem statement, all variables and given/known data
    You and a friend are sitting in the outfield bleachers of a baseball park 140m from homeplate. The temperature is 20*C. YOur friend is listening to radio comentary with headphones while watching. There is a microphone located 17m from home plate to pick up the sound as the bat hits the ball. The sound travels as an EM wave a distance of 75000 KM by satilite from the ball park to the radio.

    2. Relevant equations
    When the batter hits the ball who will hear the "crack" of the bat first ? What is the shortest time interval between the bat hitting the ball and one of you hearing it ? How much later does the other person hear the sound?

    3. The attempt at a solution

    I am not sure where to start this problem. I know t can be found using d/c. However I do not know how to factor in the distance for the microphone and the satilites.

    Should I be using c= 3x10^8 m/s?

    any help would be fantastic

    Thank you
  2. jcsd
  3. Mar 6, 2012 #2


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    Gold Member

    The batsman hears first!
    The formula:
    Velocity of sound in air = 331+(0.6)*temperature
    I hope you can find a way to manipulate this (change 331 into 3*10^8 and 0.6 into..i don know.)
  4. Mar 6, 2012 #3
    You must find out how long it takes the SOUND to travel 17m (make sure to correct for the temperature), and then add that to the time it takes for the LIGHT to travel 75,000km. Compare that to the time it takes the sound to travel 140m to the outfield bleachers.
  5. Mar 6, 2012 #4
    Thank You Thank You :) your the best
  6. Mar 6, 2012 #5


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    Gold Member

    Guys. We guide. We don't feed members the answers.

    This is in the rules, which you agreed to.
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