Things People Learn Wrong in School?

  • #51
sophiecentaur
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I'm saying that we'd need some details of this 'special' Applied Maths treatment before we could be confident about its existence. Any other treatment of friction would have to be a bit above School / College level, I think. (I'm only implying the need for evidence.)
 
  • #52
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I'm sorry I don't follow.

London University A level Applied Mathematics was the most popular applied maths syllabus in the world in its day and at its level.

Perhaps I should have acknowledged Professor Lambe's book,

Advanced Level Applied Mathematics ( dubbed "This admirable book" by The Mathematical Gazette)

more clearly as the source.

You will find the extracted text on page 63.
 
  • #53
sophiecentaur
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Perhaps you could give us a clue or summary about the basis of his notes. What extra does the method involve?

My Applied maths in 1962(ish) used the independence of friction force on area. We did Oxford and Cambridge Joint Examination Board and they had quite high cudos (afair).

But you only need to be more explicit about what you are trying to say and it may all be resolved.
 
  • #54
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Studiot post#48
I am interested in the background behind this since in my experience there were some differences of emphasis and rigour in Physics and Applied maths, but no outright conflicts as you describe.
What did you not understand about this statement?
 
  • #55
CWatters
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I'm saying that we'd need some details of this 'special' Applied Maths treatment before we could be confident about its existence. Any other treatment of friction would have to be a bit above School / College level, I think. (I'm only implying the need for evidence.)
As the person who made the original comment I wish I was able to provide that evidence but I can't. All I can remember is that one of the examining boards used was the Associated Examining Board - but can't remember if the same board was used for both Physics and Maths. I can remember the conflict was discovered in the maths class rather than the physics class.

I'm not quite willing to put it down to a false memory but who knows. It would be nice to see an old worked paper or two.
 
  • #56
BobG
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Without knowing the details, it would be impossible to know what the actual difference in approaches was.

However, if you're talking about tires.....

Deflating your tires increases your surface area and increases the coefficient of friction. The actual coefficient of friction is different for soft tires than for stiff tires, but I could see the increase in surface area providing a redneck estimate of the increase in the coefficient of friction, since it would be pretty difficult for the average person to determine what the new coefficient of friction was (especially since most people don't know the coefficient of friction of their tires when they're properly inflated).

They may be using the wrong parameter, but they're using a parameter that tends to change at least in the same direction as the parameter they really need, but have no way of knowing.

Or you have the people that realize that increasing the surface area will not increase your coefficient of friction, and so draw the even more wrong conclusion that deflating your tires cannot increase your coefficient of friction. Those will be the guys sitting in their Jeeps, stuck in the sand, waiting for a tow.
 
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  • #57
sophiecentaur
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Yes - if it were as simple as that, racing cars wouldn't be swapping their tyres every half hour as conditions change.
 
  • #58
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Friction is not the only tangentiial force acting in the interaction between the road surface and a rolling pneumatic tyre.

If you want a fir comparison with the theory of sliding friction (blocks) you should lock the wheels and tow the truck.
 
  • #59
sophiecentaur
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Friction is not the only tangentiial force acting in the interaction between the road surface and a rolling pneumatic tyre.

If you want a fir comparison with the theory of sliding friction (blocks) you should lock the wheels and tow the truck.
I think that the force would nave to be described as 'friction'. If not then you'd have to think of another name and 'friction' is a pretty catch-all term which assumes a flat surface. When would a grooved road surface become 'rails, for instance?. There again, a rubber tyre does not have linear characteristics (hysteresis and adhesion, for a start) so it wouldn't be expected to behave in an ideal way. Also, when cornering, there is slippage (work done) and the forces aren't the same as if the car were actually on rails with no slip at all.
 
  • #60
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The Octet Rule! I would have had a much better time in school and intro chem if I understood that it was mainly to C N O and F. I'm sure my teachers mentioned it at some point, but I never listened in highschool. Sometimes I feel like I wasn't old enough to appreciate what was being taught in highschool!
 
  • #61
The Octet Rule! I would have had a much better time in school and intro chem if I understood that it was mainly to C N O and F. I'm sure my teachers mentioned it at some point, but I never listened in highschool. Sometimes I feel like I wasn't old enough to appreciate what was being taught in highschool!
That's how I see a lot of people as.. but you gotta remember there are people out there who really want to learn!
 
  • #62
fluidistic
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In elementary school (when I was 8) I was taught that the surface tension of water was due to gravity: Our teacher put the end of a pencil into water and removed it very slowly until it was over the surface but the water was still sticky on it. She said that it's the same force that the Moon exerts on Earth and create tides. The worst thing is that I believed her.

I don't think someone had a similar experience but if you do, please post. :)
 
  • #63
epenguin
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same for singers breaking wine glasses (at least it doesn't work for non defective glasses)
I think that one was more often seen a century or more ago when the average glass was a lot less perfect and had stresses in it.

I only saw it once, sitting at a restaurant table this thick glass suddenly exploded and all that was left was a fine glass powder (except for the stalk I think).
 
  • #64
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I think that one was more often seen a century or more ago when the average glass was a lot less perfect and had stresses in it.

I only saw it once, sitting at a restaurant table this thick glass suddenly exploded and all that was left was a fine glass powder (except for the stalk I think).
Oh yes glass can do that.
 
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  • #65
epenguin
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I saw in an elementary physics book which was the book set for some students I briefly taught, about hydrostatic pressure, that deep sea fish had large mouths so as to equalise pressure outside and inside them and not be crushed.
 
  • #66
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The Octet Rule! I would have had a much better time in school and intro chem if I understood that it was mainly to C N O and F. I'm sure my teachers mentioned it at some point, but I never listened in highschool. Sometimes I feel like I wasn't old enough to appreciate what was being taught in highschool!
Can you please elaborate?
 
  • #67
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In about year 7, first year of secondary school in the United Kingdom, most of my friends, my history, drama and English teachers had all tried, rather painstakingly, to convince me that 0/0 is 0. I knew this was false, but I didn't really understand why. Most of the world population would agree with them sadly. I did not have the chance to ask my math teacher. Then again, this was year 7. I now know that 0/0 is much more complicated than that...

BiP
 
  • #68
sophiecentaur
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In elementary school (when I was 8) I was taught that the surface tension of water was due to gravity: Our teacher put the end of a pencil into water and removed it very slowly until it was over the surface but the water was still sticky on it. She said that it's the same force that the Moon exerts on Earth and create tides. The worst thing is that I believed her.

I don't think someone had a similar experience but if you do, please post. :)
I have read the equivalent level of nonsense on some posts on PF in the past. When challenged, the posters have managed to get very stroppy, too!.
 
  • #69
sophiecentaur
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Dang me if the very next post I read (not on this thread) wasn't the finest of example of that. Teachers don't have a monopoly.
 

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