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Help with Doppler effect radar question.

  1. Feb 6, 2013 #1
    Can any of you help. I am trying to fight a speeding ticket with a written declaration. To be honest I feel it was so unfair I was going with the speed of traffic and marked me as going 6mph more. I am sending the court explaining how I believe this was wrong and a radar error. Taking Physics 101 in college and not really good at it as I'm just learning but feel like I can win if I explain this correctly.

    If my wave velocity is 71mph, Source of velocity is -1 (being the cop with his gun) what would be my source of frequency f0 ?

    Also does is makes sense that the doppler effect is affected if there's other cars so close and around me and therefore his gun is inaccurate? I'm traveling in a caravan with 5 cars behind me and 4 cars so close in front..

    I hope I win this court battle as I'm a good citizen and feel so unfair. 65mph limit and I was going 71mph. Plus I'm a broke college student.
     
  2. jcsd
  3. Feb 6, 2013 #2

    berkeman

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    Trying to discuss Doppler math isn't going to help. You would need to be able to prove that some other vehicle near you was the one that was going faster than you were, and that vehicle should have been the one to get the ticket. Did the officer write you for 71mph or 77mph? How did he single you out of the line of traffic? Perhaps it was for your speed from a time before you joined that line?
     
  4. Feb 6, 2013 #3
    Berkeman NO! it was 71MPH he cited me for 6mph more than the speed limit. He said I touched the center divider line, I think that's why he singled me out. Plus it was superbowl Sunday so they were pulling over everyone and their grandma.
     
  5. Feb 6, 2013 #4

    berkeman

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    But I got the feeling from your OP that you said you were actually doing 71mph...?
     
  6. Feb 6, 2013 #5
    No I wasn't...but he marked that on my ticket. It was the car in front for sure...
     
  7. Feb 6, 2013 #6

    berkeman

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    Ho fast do you think you were going? And I thought you said all the cars were basically going the same speed...
     
  8. Feb 6, 2013 #7
    I was about 65mph so was everyone else but the car in front was going a bit faster and as soon as he saw the cop parked pushed the breaks...but I don't have any evidence for that ;(
     
  9. Feb 6, 2013 #8
    Call up the officer that issued the ticket and ask to meet so you can discuss the ticket. They WILL meet with you over the matter. Be nice, talk to him about it, plead your side of the story, perhaps he will understand that a mistake could have taken place and drop it.

    The majority of reports that I have read about people beating the Lidar gun in court all boil down to the guns calibration dates being wrong. Though, I don't know where one would go to get that information after-the-fact.
     
  10. Feb 6, 2013 #9

    berkeman

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    Sorry, I don't believe you. Radar guns are not that inaccurate.
     
  11. Feb 6, 2013 #10

    phion

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  12. Feb 6, 2013 #11

    Evo

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