Should a student correct a teacher?

[Shooting Star]

How do you correct a teacher politely?

The post "Pulley Problem" was put up by member temaire in: https://www.physicsforums.com/showthread.php?t=209450

The answer to this is 27 N. I asked him to clarify with his teacher. He sent a PM to me, part of which I’m putting up here with his permission.

Msg from member temaire
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I did ask my teacher just yesterday, and she told me that she discussed the question with the physics department head, and he said that the answer is 30 N. I asked her if she could show me how the answer was 30 N, but all she said was "in the end, the Newton meter is still being weighed down by two masses that add up to 3.0 kg." …
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The teacher discussed this with the Head and both decided on an incorrect concept? I’m slightly shocked and dismayed. But my concerns are for future students. Does anybody have any idea how to put across the correct solution to the teacher and the dept head?

 

[George Jones]

How do you correct a teacher politely?

The post Pulley Problem was put up by member temaire in: https://www.physicsforums.com/showthread.php?t=209450

The answer to this is 27 N. I asked him to clarify with his teacher. He sent a PM to me, part of which I’m putting up here with his permission.

>>
I did ask my teacher just yesterday, and she told me that she discussed the question with the physics department head, and he said that the answer is 30 N. I asked her if she could show me how the answer was 30 N, but all she said was "in the end, the Newton meter is still being weighed down by two masses that add up to 3.0 kg." …
>>

Discussed this with the Head and both decided on an incorrect concept? I’m slightly shocked and amazed. But my concerns are for future students. Does anybody have any idea how to put across the correct solution to the teacher and the dept head?

Maybe a more pedagogical wording of the following.

Replace the left 1 kg mass with a sequence of smaller and smaller masses. As the left mass goes to zero, the acceleration of the right mass goes to g, the tension in the string goes to zero, and reading on the meter goes to zero.

The limiting case is the same as no left mass, but with someone holing onto and then releasing the left end of a massless string that has a 2 kg mass on the right. surely no one would think that the string pulls down on the meter with any force, let alone the 20N of force the teachers' analysis would give.

 

[Shooting Star]

My point exactly. The question is, who's going to tie the bell?

 

[Chi Meson]

The answer is 27 N. Have your teacher, and the dept head, read the thread.

 

[Schrodinger's Dog]

Our chemistry teacher used to pay us a pound if we spotted any mistakes. Good system really, certainly made people more likely to pay attention.

 

[Defennder]

Why not tell him to print out a few good posts from the thread and hand it to the teacher? Saves them the trouble of having to visit this forum.

 

[Kurdt]

Yes, I think the best thing to do is to say you're still having difficulty and ask them to go through your fully worked answer and point out where you may have made a mistake. Thats the most diplomatic option. You could of course say anything you like as long as they see the full working.

 

[Math Jeans]

My Chinese teacher gives out an extra point whenever we find mistakes.

So far the rest of the class has a total of 1 point this semester, and I'm up to 12.

I don't normally think of how I should present the correction, I think my teacher is just always happy when we figure these things out.

 

[NeoDevin]

Most teachers don't mind if you point out their mistakes (as long as you're not rude about it), however there are a few who don't like to admit to being wrong.

 

[Poop-Loops]

We find mistakes in my physics classes all the time. It's usually "shouldn't there be an h-bar there?" or something like that, just an oversight, but we've also found errors in homeworks, or just in lecture doing something weird.

The profs are always fine with it. Nobody is perfect, and it's better to get help from the class than to keep dwelling on the mistakes.

This prof just reeks of arrogance, and I doubt she talked to the department head.

 

[JasonRox]

I never bother to point out mistakes because a lot of times if you know what you're doing, you should know the prof. made a mistake and it is irrelevant.

I hate it when people pointing the little mistakes. Such a waste of time. Very annoying too.

 

[Poop-Loops]

BS. A lot of the times, I'm confused that he didn't put a constant out front, or made it look like taking the gradient instead of the divergence (no dot), so I ask, to make sure whether he did something I don't understand or just made a mistake.

It's better than wondering for the rest of the class. And if you have that question on your mind, there's a good chance someone else does, too.

 

[Moonbear]

Most teachers don't mind if you point out their mistakes (as long as you're not rude about it), however there are a few who don't like to admit to being wrong.

Indeed, and those who won't admit to the ocassional mistake are often the bad teachers. It sounds like the teacher doesn't even know how to solve the problem, and is just going by someone else's answer, which is really scary.

I agree with the suggestion to take the worked out problem to the teacher and ask to have it pointed out where you made your mistake...not that you made a mistake, but it's a diplomatic way of approaching the issue that won't put the teacher on the defensive (s/he shouldn't be on the defensive, but if there is an issue of the teacher feeling insecure in the subject they're teaching here, it's entirely possible they will be anyway).

As Jason points out, in a more general answer, one should be careful over whether they are getting overly nitpicky, and constantly just irritating everyone by pointing out minor mistakes ("OOOH OOOH, Miss Smith, you forgot to write the negative sign there, and you just said it was negative!"), but if they are grading you and marking your answers wrong based on their own mistakes, it is certainly worthwhile to discuss with them your answer and why you think there's an error in the accepted answer...as long as you're open to the possibility that the teacher also could be right...but they need to be able to show you where your error is in that case. If they're teaching an entire concept incorrectly, that is certainly worth bringing up...or at least point out the class' confusion in trying to understand what is being taught, "The book says..., and you're saying..., I'm a bit confused, because those seem incompatible to me."

 

[Shooting Star]

I hate it when people pointing the little mistakes. Such a waste of time. Very annoying too.

This one is NOT a "little" mistake.

Indeed, and those who won't admit to the ocassional mistake are often the bad teachers. It sounds like the teacher doesn't even know how to solve the problem, and is just going by someone else's answer, which is really scary.

You have put your finger on it. That is why I expressed concern for the future students and started the thread.

(BTW, many people are thinking this is happening to me. Please read the first post. It has happened to PF member temaire.)

 

[Schrodinger's Dog]

I never bother to point out mistakes because a lot of times if you know what you're doing, you should know the prof. made a mistake and it is irrelevant.

I hate it when people pointing the little mistakes. Such a waste of time. Very annoying too.

I hate grammar and spelling Nazis, but then I'm dyslexic, so... Pointing out a there instead of a their when the context is clear is annoying and a waste of time, and likely to divert threads or discussions or education. I tend to agree if the mistake is large enough in a particular case and is not just nit picking then it's worth clarifying, after all even an incorrect sign or a decimal place can make the answer so far removed that it no longer resembles the answer. In this case I think it's a good idea to bring it up, after all it might confuse people, if there answer is not the same as the actual answer.

 

[Darkiekurdo]

My maths teacher told me that x/0 = 0, so I had to correct him.

 

[Schrodinger's Dog]

Well you had to that's undefined except in certain mathematical frameworks. Silly sod.

 

[Darkiekurdo]

Well you had to that's undefined except in certain mathematical frameworks. Silly sod.

Indeed.

 

[lah214]

If she's a good teacher she shouldn't get offended. The best teachers I've had are the ones that love it when people correct them.

 

[Astronuc]

Should a student correct a teacher? Yes
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How do you correct a teacher politely? Politely


I've had to correct my teachers in that past, and I've been corrected (yeah I know it's hard to believe the latter )


One corrects a mistake politely and thoughtfully, as in "I think you mean . . . ." or "I think you want to do . . . . " or something like that.


In the case of this problem, an example of Atwood's machine, in the static case, i.e. no acceleration of the masses, the force on the spring would be ~30N. However, since the larger mass is accelerating downward, it has a reduced weight. The force on the spring is equivalent to 2T, for which others have correctly demonstrated is ~27 N. This is the dynamic case.

 

[Poop-Loops]

Ugh, I just had a flashback to last year when we were doing 1/r potentials. We went over gravity and E&M potentials. One has a minus sign, one doesn't. I pointed out that the professor had two that were the same (forgot if they were both minus or both positive) and said he can't have it both ways. Took him a moment to notice it himself, and then goes "Ahh yes, of course." Proceeds to correct it and asks me "And why is that?" and (mind you, this is 2nd year physics. No quantum mechanics yet, no particle physics class, etc.) I answer "Because you can't have negative mass." And he cuts in and says "Because the Graviton has spin 2."

God damn. He HAD TO one-up me.

Still, I liked the teacher and even though he's arrogant, he's still great. I mean, he acknowledged the mistake and all, but he had to show off. :(

 

[Andre]

Correcting your teacher? Put question marks behind every statement.

In accordance with Newtons first law of motion, every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it. But wouldn't that mean that, if there is a change in the motion, that there must be a net force acting? Wouldn't that mean that the vectors do not add up to zero as it would when the spring was indicating 30N? etc

 

[Chi Meson]

Correcting your teacher? Put question marks behind every statement.

In accordance with Newtons first law of motion, every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it. But wouldn't that mean that, if there is a change in the motion, that there must be a net force acting? Wouldn't that mean that the vectors do not add up to zero as it would when the spring was indicating 30N? etc

So, the "30N" answer violates all three of Newton's laws, as well as:
Conservation of Energy Principle
Law of conservation of momentum
Impulse-Momentum theorem
Work-Energy theorem
and
common sense

 

[Shooting Star]

So, the "30N" answer violates all three of Newton's laws, as well as:
Conservation of Energy Principle
Law of conservation of momentum
Impulse-Momentum theorem
Work-Energy theorem
and
common sense

I wouldn't put too much trust on the last one where Physics problems are concerned, but all the others, yes. In fact, the argument of the teacher and her colleague, as narrated by the OP (1st post), seemed to be based on "something" like that only...

 

[Chi Meson]

In fact, the argument of the teacher and her colleague, as narrated by the OP (1st post), seemed to be based on "something" like that only...

Only too true.

I wonder if the teacher had incorrectly read the problem? I know I have done that before, sometimes assuming a problem is much more difficult than it was supposed to be.

 

[Shooting Star]

Only too true.

I wonder if the teacher had incorrectly read the problem? I know I have done that before, sometimes assuming a problem is much more difficult than it was supposed to be.

On my advice and after seeing my solution, the OP had approached the teacher. She had discussed it with the dept head, and had both come to the conclusion that it had to be 30 N. No misreading or misinterpretation here, I think.

 

[Moonbear]

No misreading or misinterpretation here, I think.

Other than missing the big "frictionless pulley" that's also in the drawing, and that the two weights are attached to opposite ends of the same string.

 

[VashtiMaiden]

How do you correct a teacher politely?

Teacher, excuse me, but the correct answer is...? or teacher, you made a mistake...

haha.. how would i know.