What are vvvdat tables and how can they help with introductory physics homework?

[Gokul43201]

This is space to start writing up and discussing ideas, structure and content for a possible Physics Homework FAQ type of sticky thread.

Note : This is an attempt to implement marlon's idea in the Feedback Forum

 

[Gokul43201]

Let me start this rolling : I think most of the following questions belong in the K-12 section. Here are a few :

1. What is a "good" approach to solve a typical kinematics problem ?

(equations of motion under constant accel - average velocity - cases when a = 0 - graphical representation - some examples - relative velocities - addition/subtraction of vectors - some examples)

2. What is a "good" approach to solve a typical Newtonian mechanics problem ?

(free body diagram - resolution of forces - how friction works - resultant/net force - Newton's second law - when to use conservation principles and which ones to use when - some examples)

3. Kinetic theory of gases, anyone ?

(gas laws - postulates of the kinetic theory - how to think of temperature in terms of mean kinetic energy - velocities, molecular weights, etc - some examples)

4. How does one think about heat and related problems ?

(energy conservation - specific heat capacity : solids/liquids/ideal gases - latent heats - some examples - heat transfer : conduction/convection/radiation - thermal conductivity/Newton's law of cooling/Stefan- Boltzmann equation - examples)

5. Geometric and wave optics ?

(laws of reflection/refraction - refractive index - total internel reflection - mirrors and lenses - sign conventions (or how not to follow them) - interference - diffraction - some examples)

I"m tired, but there's more topics, like sound, hydrostatics, (hydrodynamics ?), and the basics of electrostatics, electrodynamics.

Am I asking us to write a textbook ? Certainly not ! I don't imagine that any of the above topics will require more than a page, and even that's a lot. Diagrams will have to be handled through attachments.

Anyway, throw in your ideas and objections. Let's see what comes of this...

 

[arildno]

One issue many are confused about, is the difference between material and geometric physical systems.
A material system consists of the SAME material particles over time, whereas a geometric system needs not to consist of the same particles.

The laws of mechanics are formulated with respect to a material system; if we want to to find the correct laws for geometric systems, we need to tweak the laws a bit.
In particular F=dP/dt is no longer in general true for the geometric system, since we need to take into account the possibility that new momentum (in the form of new particles) has entered our system, or that momentum has been lost in that some old particles have left the system we're observing.
A typical example of a geometric system is the rocket problem (where old mass is continually lost through fuel ejection)
Another example is whatever fluid is passing through a specified tube of interest.

I might be willing to post something about this if that is considered interesting enough.

 

[marlon]

Err this is not exactly what i had in mind...But, please go along...

marlon

 

[ZapperZ]

I do have one suggestion for this, and I would be willing to volunteer to write it (I already have some form of it written down since I have used it before when I taught intro physics).

I'd like to see something to the effect of "How To Solve Physics Problems".

I see many instances where students have very bad problem-solving technique. One such example is that they tend to plug in values way in the beginning of their work, and then get stumped when they are not given some values that they think they need. This is a major pitfall for most students learning this subject, that they somehow do not realize that they are better off solving it algebraically first. It is also easier for the rest of us to follow the work when it is shown symbolically rather than tracking what those numbers represent.

There are many others, but I think, in addition to some of the common problems being shown in the FAQ, we should also teach them how they should solve a problem.

Zz.

 

[Clausius2]

The only way I could help would be talking about Fluid Mech (I have noticed there are sometimes questions about Hydrostatics and Bernoulli equation), and heat engines-thermodynamics.

I think most of physicists here are much better to explain basics mechanics and introduction to physics.

Let me know.

 

[Andrew Mason]

There are many good suggestions here. I think a FAQ could contain some general things, such as Zapperz' suggestion. But I think you are going to find it to be an unwieldy project that will be very time consuming to create and maintain.

It might be better to prepare lists of model question/answers from among the archives for each type of problem and link to them separately from the FAQ page. Certain problems keep coming up over and over and it may be that students find it difficult to find them through the search facility.

AM

 

[Gokul43201]

I do have one suggestion for this, and I would be willing to volunteer to write it (I already have some form of it written down since I have used it before when I taught intro physics).
...
There are many others, but I think, in addition to some of the common problems being shown in the FAQ, we should also teach them how they should solve a problem.

Zz.

Zz, I like this idea. If you could write this up and post it here, that would be a good start.

It might be better to prepare lists of model question/answers from among the archives for each type of problem and link to them separately from the FAQ page. Certain problems keep coming up over and over and it may be that students find it difficult to find them through the search facility.

AM, I think this would defeat our philosophy of helping the students think for themselves. If students are going to have access to complete solutions, let's at least leave it be hard for them to find such solutions. I think the existence of searchable archives with problems entirely worked out over the course of the thread is in itself a (possibly unavoidable ?) drawback. It is the easy way out; we shouldn't be making it easier, should we. Anyway, that's just my opinion. Others are welcome to join in with theirs.

Marlon, this was your brainchild ! Even if this is not what you had in mind, please throw in your ideas. I thought I was providing a space to explore your idea, but if this is not it, feel free to talk about it here (if it's related) or in the original Feedback Forum thread.

 

[arildno]

I mentioned to marlon in a PM that possibly we might create a section on how to choose the most convenient/easiest description of a problem in physics.
A few examples from classical mechanics:
1) How should we place our coordinate axes to get the "simplest" description?
2) Should we choose an inertial or non-inertial frame?
3) What control volume/physical system ought to be chosen in order to simplify the arguments?
4) Conservation perspectives vs. force/torque-perspectives
Perhaps it would be illuminating to use examples where there also exist at least one other, but lot more difficult way of doing the problem, and show both ways in full.

 

[Gokul43201]

Here's what I think we want to achieve in this thread :

1. Decide whether some form of a Physics Homework FAQ is a good idea at all.

2. If the answer to 1 appears to be 'yes', then what kinds of questions must the FAQ address : only general stylistic/approach oriented questions such as Zz's suggestion; or/and more specific (though still staying broad for the most part) physics questions as well ?

3. Make up a list of important questions to answer. And figure out how (approach and structure) we want to answer them.

4. Pick volunteers to prepare a first draft towards answering one or more of the above questions.

5. Make suggestions/criticisms and through that process amend the drafts to arrive at a final set of answered questions.

I request that we start off try to address the points in this list in each of our posts (in addition to whatever else anyone wants to say)

For my part, I think the FAQ is a good idea, but as AM has pointed out, may be a mouthful after all. I wouldn't mind taking up one or more of the questions I've proposed, if they still stand after further scrutiny.

 

[chroot]

I believe we should follow the style of the Dr. Math program at http://www.mathforum.org. I am also a contributor there and feel it works well.

They have a pretty detailed FAQ that provides reference material -- equations, simple problem-solving techniques, fair and thorough answers to perennial questions like "Does 0.999... = 1?", and so on. Then, in addition, they provide a searchable archive of good questions, together with (sometimes several) good answers -- a sort of "hall of fame" of math instruction.

- Warren

 

[Galileo]

I bought Polya's "How to Solve it" a few months ago and it's a real gem.
A detailed and carefully crafted book addressed to the problem of solving problems.
I can identify myself in lots of stuff he's written. I don't want to copy Polya (that'd be plagiarism), but do something similar that is specialised for the use of solving physics problems.

In my opinion, the main goal is to learn students to think structurized instead of juggling with vague bits of information here and there ("should I use this?") and some formulas ("oh, let's plug it in the equation, is this right?").
So I'm willing to write a general outline to such problems and why and when you should or shouldn't use a specific method. What model are we using and what are its limitations etc. Then a few sample problems where the solution is not only outlined, but where the thought process is written down. Usually the problem can be solved by asking the right question. By taking the student through some of these processes, he/she may get an idea. Since nothing will be learned if he/she doesn't do stuff him/herself, I think a test or quiz is a great idea too.

Those are my thoughts on the subject. I can't claim to know they will work, since I`m not a teacher like some of the others here (I`m still a student myself) so my experience is limited, but I aspire to be a good teacher next to a physicist.

 

[marlon]

Guys, i think Warren made a very good point and he provided a very nice link. Like i have feared, this thread is starting to look like what we possible can do, but that's useless. Now, i realize that some discussion will be necessary but i suggest we do it like this : i have started a thread in the Homework section (i am hoping it will become a sticky) where i posted some examples of Newtonian mechanics. I have also pointed out (in the last post there or in my suggestion) which route to follow. I have started on specific things...just check it out. Now if there are suggestions and/or corrections, i think we should PM-them to each other. I know for sure that arildno is willing to contribute and he is willing to communicate through PM. I urge you NOT to communicate through posts because we will end up with what we have here : a sequence of posts that are indeed valuable to the authors but NOT to the future users of this thread. I think we should get started like i did (and let's pm-for extra texts that should be added, so we know of each other what we are doing) and continue that specific road. There is ofcourse lots of room for discussion via pm or this thread but let's keep the thread that i started to the actual problem solving posts. If someone wants to post something there (and i very much hope you will) let it be specific solutions to specific problems on the topic we are dealing with right now : Newtonian mechanics.

Besides, i also would like to make many references in that thread to posts that have been made in the homework section in the past. Like this, the users will STAY IN this forum and they won't be redirected to other sites outside this forum. Just thought the administrators would like that :)

marlon

 

[marlon]

I posted some preliminary texts here:

https://www.physicsforums.com/showthread.php?t=72040

regards
marlon

ps : i could really use some pictures to go along with the exercises...Anybody got some ? Otherwise i will have a lot of scanning to do...

 

[Gokul43201]

Arildno's thread on the classical mechanics of open systems can be found here :
https://www.physicsforums.com/showthread.php?p=538334#post538334

Give it a look-see and post any suggestions here.

 

[marlon]

That's gread work arildno...

marlon

ps : Gokul, could you delete dexter's post in my thread ? thanks

 

[e(ho0n3]

I think what arildno is doing with the post [post=538334]Homework help: Classical Systems With Variable Mass And Other Geometric Systems[/post] is really cool.

Oh, and sorry about interrupting the post like. I didn't know it had a higher purpose.

So, what does one do when one wishes to comment on or question a statement in a post such as the one above? I mean, I consider arildno's post above to be overkill for an FAQ section.

 

[Gokul43201]

So, what does one do when one wishes to comment on or question a statement in a post such as the one above? I mean, I consider arildno's post above to be overkill for an FAQ section.

The discussion happens here. Post your suggestions to marlon's or arilno's threads in this thread, and leave those intact.

 

[arildno]

I think what arildno is doing with the post [post=538334]Homework help: Classical Systems With Variable Mass And Other Geometric Systems[/post] is really cool.

Oh, and sorry about interrupting the post like. I didn't know it had a higher purpose.

So, what does one do when one wishes to comment on or question a statement in a post such as the one above? I mean, I consider arildno's post above to be overkill for an FAQ section.

I would rather say I'm doing a bloody massacre of FAQ's there..

The reason why I wanted to do this particular thread, is that variable-mass classical systems are, in general, very cursorily dealt with in most introductory physics text (perhaps you understand better now why..)

I find, however, that this cursory treatment is precisely the type of treatment which easily can lead to misunderstandings of the issues involved. And I dislike that!
Thus, I felt that this particular topic ought to be treated in some greater detail..
And again, feel free to PM me if there is some particular question you don't think warrants a post in this thread.

 

[arildno]

That's great work arildno...

Thanks for the support.
I look forward to both constructive and destructive criticisms of my thread..

 

[Reshma]

Just another humble suggestion here :-)

How about a thread on vector analysis including divergences, curls, fundamental theorems, line, volume and surface integrals? These can aid solving problems in electrodynamics etc. Or is this thread supposed to be in a math forum?

 

[Gokul43201]

Thanks for the support.
I look forward to both constructive and destructive criticisms of my thread..

Arildno, I have one little suggestion. Can you also throw in references to texts, papers, review articles or online resources that you think will be useful for supplementary reading ?

 

[arildno]

A good suggestion!
I'll see if I can come up with something..

 

[govinda]

(i)appreciate the effort,
infact i would have saved a lot of time if some1 had explained when momentum is conserved ... why it is conserved . the relationship between momentum conservation ,centre of mass Newtons thrird law and impulses . also solve a few probelms ab initio for example some simple conservation of momentum problems considering small particles and integrating as you go along so that you get a feel of moment of inertia y we use it, how it simplifies calculations . I am still not very clear on some of these "elementary questions" i had fun finding my own solutions but was not confident since i hadnt cross checked them .
basic study materials are genreally full of holes ...in attempting to get the central point across confusing questions arent addressed and asking the school teacher isn't an option! (at least in my case)
anway..
great initiative !

 

[cscott]

Could you add the level of the material (like how the homework forums are devided up, or even more specific) and maths needed for the material you're covering?

Also, maybe a wiki would work (maybe only the "science advisors" and "homework helpers" can edit it.) I know another forum like this (computer science, though) where the the people active really know there stuff and their wiki FAQ seemed to work nice.

Here it is if you wanted to look: http://www.mega-tokyo.com/osfaq2/

There are a lot of very good posts in journals (like ZapperZ's "So You Want to Be Physicist") along with various sticky threads that could be added too, but I guess I'm kind of wandering away from just a homework help FAQ.

 

[cscott]

...were my ideas that bad?

 

[marlon]

...were my ideas that bad?

Nono, you had some great suggestions but i think you need to be patient for just a little while longer . Your ideas are great and we thank you for that. However just one remark, the content of 'So you want to be a...' is not suitable for a FAQ thread because it does not solve specific problems you see ? I mean this knowledge is not relevant in solving physics or Math related problems, wouldn't you say ? The content of this thread can be found on any science faculty webpage of almost every self respecting university out there, so why bother posting such general and obvious knowledge in a FAQ thread ? It really is a bit superfluous...


regards
marlon

 

[Astronuc]

Just another humble suggestion here :-)

How about a thread on vector analysis including divergences, curls, fundamental theorems, line, volume and surface integrals? These can aid solving problems in electrodynamics etc. Or is this thread supposed to be in a math forum?

I have been wondering about this myself. Is there such a thread in the Math forum? If not, I would be pleased to create one.

I think an understanding of the physical signifcance of gradient, divergence and curl is very helpful to students in physics and engineering.

There is an excellent discussion of this matter in "Mathematics of Classical and Quantum Physics", by Frederick W. Byon, Jr. and Robert W. Fuller. So I imagine any thread on this subject would be pretty much a regurgatation of Byron and Fuller.

BTW, I like marlon's and arildno's treatments of the subjects they did. Like e(ho0n3 mentioned, I have not seen a treatment like the one by arildno in "Classical Systems With Variable Mass And Other Geometric Systems". I think this partially addresses the matter discussed in "lessons" in the Feedback forum.

 

[marlon]

Great point Astronuc,

besides i have already written a text on the definition and use of tensors because lot's of college students have problems with this concept. The text is somewhere in my journal.

regards
marlon

 

[Reshma]

I have been wondering about this myself. Is there such a thread in the Math forum? If not, I would be pleased to create one.

I think an understanding of the physical signifcance of gradient, divergence and curl is very helpful to students in physics and engineering.

Thank you for addressing my question . I started learning about divergences, gradients and curls straightaway in electrodyanmics without any mathematical background to it. I don't have much understanding about the physical significance of gradients etc. So it would be very helpful if someone starts a thread on vector calculus.