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Member (Idle past 504 days) Posts: 3645 From: Indianapolis, IN Joined: |
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Author | Topic: Using your common sense to solve a physics problem. | |||||||||||||||||||||||
coffee_addict Member (Idle past 504 days) Posts: 3645 From: Indianapolis, IN Joined: |
I was just talking to a friend... not really a friend but more like someone that I just met in the hall way... about physics and stuff. I had a lot of free time, so we talked for quite some time. It turned out that he didn't really know that there are physics problems that deal with stuff much more complicated than the ones we see in kinematics. He didn't really know that there are problems such as the ones dealing with electromagnetism where it's entirely calculus based. With kinematics, you can pretty much get away with only basic knowledge of algebra. However, it gets a lot more complicated than that in higher disciplines of physics.
This got me thinking. If the rat (please don't take offense in me calling you the rat, I tend to do that with people... like the frog) thought that common sense alone could give you enough skill to solve such a problem as a car breaking to stop, it crossed my mind that may be there are members on this board that are still under the impression that physics is only about solving algebraic equations and dealing with everyday stuff. So, here is a slightly more difficult problem just so you wouldn't think that physicists are fruitcakes. No, I don't really expect any non-physicist to be able to solve this. It's relatively simple, but it's quite beyond everyday common sense, I'd say. Find the electric field a distance z above one end of a straight line segment of length L, which carries a uniform line charge of λ. What happens if z is approaching infinity? Here is the equation necessary for this problem. E = 1 / (4 * pi * ε) ∫ [(λ r')/R2] * R^ dl' where E = elctric field, ε = permitivity constant, r' = field point, R = distance between a source charge point on the line segment and the field point r', and R^ is the direction of the magnitude. Here is a picture to make it easier.
As I know it, there are 2 ways to do this. One of them will take you 2 pages to do, and the other will take you about 4 or 5 steps. Not supprisingly, I still have trouble when doing the long way because it's too complicated. Have fun. The Laminator For goodness's sake, please vote Democrat this November!
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Rei Member (Idle past 7040 days) Posts: 1546 From: Iowa City, IA Joined: |
I don't care if you would have suggested that change; that is completely off topic. You were asked for the rammifications of a proposed change. You pointed only to minor rammifications, and completely ignored the major ones (which led to collapse). You completely failed, where a mathematical analysis would easily have succeeded.
This message has been edited by Rei, 09-27-2004 01:25 PM "Illuminant light, illuminate me."
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riVeRraT Member (Idle past 443 days) Posts: 5788 From: NY USA Joined: |
Please lam, I never said jerk physists.
I also never meant all scientists. I am so intrigued by magnetism. I really wish I could go to college and learn more about it. I just don't have the time. I also don't have the time to finish the first problem, but I promise I will. I will also consider trying to at least understand this problem as well. When dealing with common sense, I fully realize that common sense can get you in trouble. Common sense does not also mean that you can figure something out in a day or a week, or whatever, but that you can indeed one day figure it out. Regardless of your training. Those who recieve training and pocess common sense, will figure things out much easier, and see things more clearly. Tell me, do you think just because you can figure this out on paper, means that you can see whats going on? You might, but what about the next guy?Isn't there a big difference between being taught formulas, and trying to figure them out on your own?
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riVeRraT Member (Idle past 443 days) Posts: 5788 From: NY USA Joined: |
What is λ ?
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Percy Member Posts: 22498 From: New Hampshire Joined: Member Rating: 4.9 |
Lamba usually refers to wavelength.
--Percy
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Melchior Inactive Member |
quote: Lambda is a rather frequent symbol and you can't really assume it means wavelenght unless you are talking about wave-physics or similar fields. This message has been edited by Melchior, 09-27-2004 05:04 PM
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coffee_addict Member (Idle past 504 days) Posts: 3645 From: Indianapolis, IN Joined: |
Lam writes: Find the electric field a distance z above one end of a straight line segment of length L, which carries a uniform line charge of λ. What happens if z is approaching infinity? In other words, lambda in this case is the uniform line charge.
the rat writes:
Yes, I do really see what's going on. One of the most wildly misconceptions regarding physics is that physicists can't really understand what the equations are saying. That is not true. Tell me, do you think just because you can figure this out on paper, means that you can see whats going on? You might, but what about the next guy? The average person might not know what the equations are saying, but if you are studying physics you better know damn well what the equations are saying.
Isn't there a big difference between being taught formulas, and trying to figure them out on your own?
Actually, I did figure out that equation on my own. The only reason I posted it here is because I didn't expect non-physicists to be able to. It's like me writing a paper on economics... I wouldn't know where to begin. Again, if you are studying physics and you can't derive this equation on your own, then you have a problem. This message has been edited by Lam, 09-27-2004 06:22 PM The Laminator For goodness's sake, please vote Democrat this November!
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tsig Member (Idle past 2936 days) Posts: 738 From: USA Joined: |
Riverrat
You did not respond to the content of my post.
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coffee_addict Member (Idle past 504 days) Posts: 3645 From: Indianapolis, IN Joined: |
Observer writes:
I'm going to say something for the rat, if I may. I think the rat was talking about egoistic engineers who think that they know everything better than the mechanics who usually deal with these things hands on. Although I am not a big fan of the rat (since he hates people like me), I think that there is some merit to the rat's point. RiverratYou did not respond to the content of my post. I've met some freshed out of college know-it-all engineers, and one of them was my brother. However, I've also encountered some know-it-all mechanics in my lifetime *ahem*. The Laminator For goodness's sake, please vote Democrat this November!
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tsig Member (Idle past 2936 days) Posts: 738 From: USA Joined: |
Why defend the rat? He said that common sense was enough to solve any problem then proved unable to understand the problem presented to him.
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riVeRraT Member (Idle past 443 days) Posts: 5788 From: NY USA Joined: |
Crap, I knew that too. If you don't do this everyday you forget. I learned that through studying ametuer radio. ok.
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riVeRraT Member (Idle past 443 days) Posts: 5788 From: NY USA Joined: |
Yes, I do really see what's going on. One of the most wildly misconceptions regarding physics is that physicists can't really understand what the equations are saying. That is not true.
I figured you knew. You would be interested in a little project I am working on here. I trying to design a more effiecient electric motor.I could probably use your knowledge to help me figure it out. But I think I am getting it anyway.
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riVeRraT Member (Idle past 443 days) Posts: 5788 From: NY USA Joined: |
You are beating a dead horse, give it up already.
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riVeRraT Member (Idle past 443 days) Posts: 5788 From: NY USA Joined: |
I don't hate you Lam. I love you.
I also like you. I have stated before, that I respect what you have to say, because your posts make sense. We just don't agree on believing in God. If we knew each other outside this forum, in the real world, we would get along. I argue things sometimes to get the truth out.I came into this forum, to preach the gospel, not knowing how really smart some of you are. It has been a great lesson for me. Its been great to discuss with you.
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Ooook! Member (Idle past 5842 days) Posts: 340 From: London, UK Joined: |
You are beating a dead horse, give it up already. I know this is a bit of a cheeky/lazy way of going about things, but can you point out the post in which you first used the term 'jerk scientist' (I've done a bit of a search and can't find it). It might be interesting to see the initial context of the comment and whether you've softened your stance after it had the desired inflammatory effect. Cheers
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