# Help with Doppler effect radar question.

• Ingrid12345
In summary, the individual is seeking help to fight a speeding ticket with a written declaration. They believe they were unfairly marked as going 6mph over the speed limit while going with the flow of traffic. They plan to explain this using their knowledge from taking Physics 101 in college. They also question the accuracy of the radar gun due to the presence of other cars nearby. The individual is hoping to win the court battle as they are a good citizen and a broke college student. They also mention that the officer cited them for 71mph, but they were actually going 65mph. Others in the conversation suggest discussing the matter with the officer or checking the radar gun's calibration date.
Ingrid12345
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.

Ingrid12345 said:
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.

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?

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.

Ingrid12345 said:
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.

But I got the feeling from your OP that you said you were actually doing 71mph...?

No I wasn't...but he marked that on my ticket. It was the car in front for sure...

Ingrid12345 said:
No I wasn't...but he marked that on my ticket. It was the car in front for sure...

Ho fast do you think you were going? And I thought you said all the cars were basically going the same speed...

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 ;(

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.

Ingrid12345 said:
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 ;(

Sorry, I don't believe you. Radar guns are not that inaccurate.

## 1. What is the Doppler effect in radar?

The Doppler effect in radar is the change in frequency of a radio wave caused by the relative motion between the radar and the object being detected. This change in frequency can be used to measure the speed and direction of the object.

## 2. How does Doppler radar work?

Doppler radar works by sending out radio waves at a specific frequency and then detecting the reflected waves that bounce back from objects in its path. The change in frequency of the reflected waves is then analyzed to determine the speed and direction of the object.

## 3. What is the difference between conventional radar and Doppler radar?

Conventional radar uses radio waves to detect the presence of objects, while Doppler radar also takes into account the change in frequency of the reflected waves to determine the speed and direction of the object.

## 4. How is the Doppler effect used in weather radar?

In weather radar, the Doppler effect is used to measure the speed and direction of precipitation. The change in frequency of the reflected waves from rain or snow can indicate the wind speed and direction within a storm.

## 5. What are some real-life applications of Doppler radar?

Doppler radar is commonly used in weather forecasting, air traffic control, and military surveillance. It is also used in sports, such as baseball and golf, to track the speed and direction of moving objects.

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