Things People Learn Wrong in School?

[Redbelly98]

"A scalar quantity has magnitude only."

A good counterexample to that is electric charge.

 

[Damo ET]

From http://www.sonicelectronix.com/cat_i6_capacitors.html: "If a vehicle has dimming headlights when music is played, a capacitor could solve that problem."

I have so many problems with this idea. For one thing, are you absolutely sure you heard the professor correctly? Surely you must be deaf by now!

And if your headlights are dimming when the music is playing, I think it means you have way too much audio system for your vehicle! And everyone sitting next to you at the stoplight probably thinks so, too!



But his was a silly statement unless he was limiting his comments to your normal home electronics. Try working at a high power space radar site that's bouncing 5 MW pulses off of space objects. They have what's essentially a small room of huge capacitors in parallel for each radar beam.

I need to first say that the Professor I am referring to was a really nice guy (a little dry but nice), and I'm not trying to bring him down for such a trivial thing. He was a little eccentric, as the stereotype suggests he should be. Mid to late 60's, and dealing with a 20 odd apprentices ranging from 17 - 30 with the bulk of the students sub 20's. I was 28/9 at the time back in 2004, with my loud music days back 10 years before that. Big caps like I suggested to him had been around since I was interested in car stereo (but not cashed up enough to buy), which would have been around 1995, so I would think that they were nothing new even when I mentioned them. But he probably wouldn't have been aware of them at the time (same for the shielded speakers). The strange thing was not that he wasn't aware of them, but that he didn't seem to be interested in the possibility that such things existed. I would have thought that a Professor of such things would be interested in the 'new' regardless of the source. I wasn't a disruptive student and got along quite well with all the Professors 'we' had, which made the whole thing even more strange.

Damo

 

[soothsayer]

One of the biggest things that gets me is the concept of relativistic mass, i.e. that mass increases at relativistic speeds. It's led to more than a few misunderstandings on these forums, mostly from thinking that a fast enough particle will turn into a black hole because of it.

Ah yes, that is a big personal pet peeve of mine.

 

[the_emi_guy]

Seriously?

We have students in Argentina being taught that the American moon landings were a hoax
and at the top of your list is the proper interpretation of "relativistic mass"?

Do we really expect high school science teachers to be able to know that their stack of books on special relativity, as well as the Wikipedia
page on "mass in special relativity" are not in line with the "modern" interpretation?

I agree with Sophiecentaur on this, and I'll take it a step further. A teacher job is not to just cram us full of "correct" facts.
It is more important that they teach students how to think for themselves, learn independently, question things,
and inspire them to want to learn more.

They can do this very effectively without having multiple PhDs.

 

[OmCheeto]

Seriously?

We have students in Argentina being taught that the American moon landings were a hoax
and at the top of your list is the proper interpretation of "relativistic mass"?

Do we really expect high school science teachers to be able to know that their stack of books on special relativity, as well as the Wikipedia
page on "mass in special relativity" are not in line with the "modern" interpretation?

I agree with Sophiecentaur on this, and I'll take it a step further. A teacher job is not to just cram us full of "correct" facts.
It is more important that they teach students how to think for themselves, learn independently, question things,
and inspire them to want to learn more.

They can do this very effectively without having multiple PhDs.

Argentina? Your profile says Maryland. Are you from Argentina? I only ask, because one of our professors from Buenos Aires passed away this last year. He was with us from 1981.

 

[Bboy Physics]

Argentina? Your profile says Maryland. Are you from Argentina? I only ask, because one of our professors from Buenos Aires passed away this last year. He was with us from 1981.

A. He's lying, he's actually in Argentina.
B. He pulled a random country that seemed third world enough.
C. He knows somebody in Argentina

Best guesses!

 

[soothsayer]

Seriously?

We have students in Argentina being taught that the American moon landings were a hoax
and at the top of your list is the proper interpretation of "relativistic mass"?

Do we really expect high school science teachers to be able to know that their stack of books on special relativity, as well as the Wikipedia
page on "mass in special relativity" are not in line with the "modern" interpretation?

I agree with Sophiecentaur on this, and I'll take it a step further. A teacher job is not to just cram us full of "correct" facts.
It is more important that they teach students how to think for themselves, learn independently, question things,
and inspire them to want to learn more.

They can do this very effectively without having multiple PhDs.

I didn't say it was the top of my list, I was just agreeing with a previous commenter. I'm not sure why you attacked me for that. It certainly is not the most egregious scientific error I've ever heard, just something that irks me as a mistake that I see very educated people, including people with physics training, make. The errors at the top of my list are only really made by teachers below the high school level and people with little scientific education, so I don't really get angry with them for understanding those things incorrectly.

There are a great many people in the U.S who believe the moon landing was a hoax as well. Though, I've never heard a teacher or professor tell me or anyone else that it was.

And it's not just high school teachers and laymen, but many people who profess to understand relativity. I just think it's a bunk term, useless and TERRIBLE to teach to students new to relativity.

 

[soothsayer]

A. He's lying, he's actually in Argentina.
B. He pulled a random country that seemed third world enough.
C. He knows somebody in Argentina

Best guesses!

I was thinking along the lines of C. Perhaps he has some knowledge of the Argentine education system or heard from some source that teaching students that the moon landing was a hoax was part of the curriculum at some Argentine schools.

 

[OmCheeto]

I was thinking along the lines of C. Perhaps he has some knowledge of the Argentine education system or heard from some source that teaching students that the moon landing was a hoax was part of the curriculum at some Argentine schools.

or D.

He, like the professor I mentioned, is from Argentina.

I work with people from all over this planet. Everyone knows what's going on at home.

 

[QuasiParticle]

"A scalar quantity has magnitude only."

A good counterexample to that is electric charge.

What?

 

[OmCheeto]

What?

ha!

 

[sophiecentaur]

Reading many of the previous posts, I am struck by the prevalence of the consumer / blame culture. Let's blame the system for not teaching us properly and leave it at that. There is another factor in the 'teaching and learning' equation. The student. We are told things about Science by teachers (and TV presenters - a much more suspect source of infor, btw). If we leave it at that and just accept it then the fault is ours as much as theirs. In the past, all we had was a textbook as an extra source and I was constantly going to mine for help with my Physics. Nowadays, there are loads of electronic sources of information (even if you happen to live in a repressive regime). There's no reason for students not checking on the Science 'facts' they are told in school.

Bringing Politics into the discussion may or may not be a good idea but the vast majority of US citizens (allegedly) reject the basic idea of evolution. This is in what we would call an enlightened and informed society. What goes on in Argentina pales into insignificance in comparison - a country who's government needs to divert the populace with issues like the Faulklands question in order to keep their power. (Just thinking back to Maggy T doing the same thing, Tony B and George W in Iraq etc. lol)

 

[Studiot]

When I was at school (<1978) two of the subjects I studied were Physics and Applied Maths. There was some overlap which sometimes caused problems.

In physics class the syllabus taught us that friction was independant of contact area. That makes sense - you might think that increasing the contact area would increase friction but it also spreads out the load over a larger area so net effect could reasonably be zero.

However the Applied Maths syllabus seemed to use a different definition of the coefficient of friction. That required us to factor in the contact area. We did raise this contradiction with our teachers but were just told we had to remember which exam we were sitting in and answer accordingly!

We must have done because we passed with good grades.

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.

Here is an extract from a University of London Applied maths text of the era concerning Friction.

" The mathematical discussion of the force of friction depends upon certain assumptions which are embodied in the so called laws of friction and are found to be in close agreement with experiment.

Law1
When two bodies are in contact the direction of the force of friction on one of them at its point of contact is opposite to the direction in which the point of contact tends to move relaticve to the other.

Law2
If the bodies are in equilibrium the force of friction is just suficient to prevent motion and may therefore be determined by applying the conditions of equilibrium of all forces acting on the body.
The amount of friction that can be exerted between two surfaces is limited and if the forces acting on the body are sufficiently great motion will ensue.
Hence we define limiting friction as the friction which is exerted when is onthe point of being broken by one body sliding over another.
The magnitude of limiting friction is assumed to be given by the following 3 laws:

Law3
The ratio of the limiting friction to the normal reaction between the two surfaces depends upon the substances from which the surfaces are composed, not on the magnitude of the normal reaction.
The ratio is usually given the Greek letter μ. Thus if the normal reaction is Rlb. wt., the limiting friction is μRlb. wt. and for given materials, polished to the same extent, μ is found to be constant and independent of R.
μ is called the coefficient of friction.

Law4
The amount of limiting friction is independent of the area of contact between the two surfaces and the shape of the surfaces, provided that the normal reaction is unaltered.

Law5
When the motion takes place the direction of friction is opposite to the direction of relative motion and independent of velocity. The magnitude of the force of friction is in a constant ratio to the normal reaction, but this ratio may be slightly less than when the body is just on the point of moving. "



All these laws are needed for the mathematical analysis of friction.
I have italicised Law 4 as it is quite clearly in line with Physics.

 

[sophiecentaur]

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.
. . . .

Law4
The amount of limiting friction is independent of the area of contact between the two surfaces and the shape of the surfaces, provided that the normal reaction is unaltered.

. .. .



All these laws are needed for the mathematical analysis of friction.
I have italicised Law 4 as it is quite clearly in line with Physics.

Indeed.
Really strange. I can't think of another version that wouldn't need to involve including the modulus of the materials involved and resulting actual contact area. But then, except for a non-linear material, all that stuff would cancel out.

As one who was taught long before 1974 (and have forgotten an awful lot of details about what actually went on), I might suggest a bit of mis-remembering?

 

[Studiot]

SophieCentaur
Indeed.
Really strange. I can't think of another version that wouldn't need to involve including the modulus of the materials involved and resulting actual contact area. But then, except for a non-linear material, all that stuff would cancel out.

As one who was taught long before 1974 (and have forgotten an awful lot of details about what actually went on), I might suggest a bit of mis-remembering?

What exactly are you saying?

 

[sophiecentaur]

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.)

 

[Studiot]

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.

 

[sophiecentaur]

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.

 

[Studiot]

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?

 

[CWatters]

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.

 

[BobG]

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.

 

[sophiecentaur]

Yes - if it were as simple as that, racing cars wouldn't be swapping their tyres every half hour as conditions change.

 

[Studiot]

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.

 

[sophiecentaur]

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.

 

[PeteyCoco]

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 high school. Sometimes I feel like I wasn't old enough to appreciate what was being taught in high school!

 

[Bboy Physics]

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 high school. Sometimes I feel like I wasn't old enough to appreciate what was being taught in high school!

That's how I see a lot of people as.. but you got to remember there are people out there who really want to learn!

 

[fluidistic]

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. :)

 

[epenguin]

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).

 

[0xDEADBEEF]

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.

 

[epenguin]

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.

 

[tahayassen]

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 high school. Sometimes I feel like I wasn't old enough to appreciate what was being taught in high school!

Can you please elaborate?

 

[Bipolarity]

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

 

[sophiecentaur]

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!.

 

[sophiecentaur]

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.