# Do you do the conceptual problems?

1. Dec 2, 2011

### Nano-Passion

Do you do the conceptual problems in your physics book? I usually feel like I get a good conceptual understanding from reading the book, and I like to get the rest of my conceptual understanding from doing the "regular" problems. Doing the problems actually increases my intuition about things much more.

Am I missing out not doing the conceptual problems?

2. Dec 3, 2011

### chiro

Hey Nano-Passion.

What do you mean by conceptual problems? How are they different from non-conceptual problems?

3. Dec 3, 2011

### Mmm_Pasta

I think he means conceptual is in "Does a magnetic field change the speed of a particle?" and non-conceptual as in quantitative problem solving.

4. Dec 3, 2011

### chiro

If that is the case, I think its dangerous not to do conceptual problems.

A lot of problems though involve conceptual and quantitative aspects though.

I couldn't imagine a physics degree without problems that were both conceptual and quantitative in nature (I would expect that the degree had quite a lot of these).

5. Dec 3, 2011

### DrummingAtom

Always, which I learned from my first semester of physics. I relied on using the math too much at first and then had some trouble when I had to make a physical assumption. Newton's 3rd law tripped me for a bit. The big truck hitting the little car which feels more force, kinda question. I know it's been said before but all the math in the world can't save you if you make the wrong physical assumption.

6. Dec 3, 2011

Staff Emeritus
Of course you're missing out. The authors put those problems in because they wanted you to do them. (Why else would they write them?)

7. Dec 3, 2011

### Nano-Passion

I don't know, I've always felt that I get all my conceptual understanding from reading the material slowly and digesting/thinking about it along with doing the problems. It hasn't failed me since, all the problems I do are pretty easy for me and I do as many problems as possible. Whenever a problem isn't easy then I figure out the conceptual hole in my understanding and then internalize that information; but that doesn't even happen much. I just see the conceptual problems as a waste of time that can be spent somewhere else.

And Chiro: in my book "University Physics with Modern Physics" by Hugh, Freedman, and Lewis Ford, the conceptual problems are just non-quantitative but qualitative questions. Kind of like: "If a has bigger mass than b and they collide what will happen."

8. Dec 3, 2011

### D H

Staff Emeritus
Conceptual reasoning is quite important, perhaps just as important as quantitative reasoning. It's the ability to see the forest for the trees. Interviewers don't ask apparently silly questions such as "How many gas stations are there in the United States?" for no reason.

9. Dec 3, 2011

### Nano-Passion

So do you do the conceptual questions? I know that conceptual reasoning is very important, but I was wondering if people actually partake in the purely conceptual questions. I don't know, as of this moment I don't really need to do the conceptual problems, but that is likely because I've taken the course in high school before. I guess that was a pretty important point to leave out. :D Maybe in Physics II I will be more inclined to do the conceptual questions.

And for the apparently silly question.. I wouldn't know how to answer that. I would reason that I see around 5-20 gas stations per city, and there are on average at least over 20 cities per state.. And since there are 50 states in the US I would just do 15*20*50. Which would equal somewhere along the ballpark of 15000 gas stations.

Would the interviewer laugh in my face?

10. Dec 3, 2011

### D H

Staff Emeritus
I've been out of college for more than 30 years. I don't do the conceptual questions.

I do ask them during job interviews so as to answer the inevitable question posed to me by upper level management, "would this fresh-out be a good person to hire?"

11. Dec 3, 2011

Staff Emeritus
Like I said before, they are there for a reason. If you don't want to put the effort in to do them, you shouldn't be surprised if you understand the material less well.

12. Dec 3, 2011

### Nano-Passion

I would be interested if you can give me another odd question to throw me off my feet. :D I'm a bit curious of what goes on in your interview room hehe.

Well its probably because I've took the course before in high school and the conceptual understanding kind of stuck with me. And actually I understand the material very well.. at the beginning of the course things were a bit confusing to me. But that is because I was having a hard time adjusting of how to do physics. In contrast, I now find everything to be relatively simple and easy.

I'll definitely look into the problems for my second course of electromagnetism.

13. Dec 3, 2011

### AlephZero

If interviewers want to have a laugh about candidates (and we do sometimes - after all, we are only human) we try our best not to do it during the interview.

But if you want learn why conceptual problems are important, go away and think of at least 3 competely different ways to answer the same "silly question", and then think about the differences between the answers you got. Don't bother to post your work here - it's for your benefit, not ours.

14. Dec 3, 2011

### D H

Staff Emeritus

15. Dec 3, 2011

### Nano-Passion

Thank you.

Haha, thanks for the reply.

16. Dec 3, 2011

### D H

Staff Emeritus
237,284 in 2003, per the Journal of Petroleum Marketing.

No. You did reason out an answer. That it was off by more than an order of magnitude is a different problem. I might ask you to rethink your numbers.

That said, no interviewer in their right mind asks this question anymore. It's too old hat. The answer is all over the 'net.

17. Dec 3, 2011

Staff Emeritus
I would have come at it differently. 200M cars, $50 a week on gas, 50 weeks a year is$500B a year. It takes between $1.5M and$2M a year to keep a freestanding store profitable, so 300,000 or so would be the right ballpark.

Or - there are 12,000 McDonalds in the US. My town has one, and 12 gas stations. So, I would estimate 150,000 or so. That's probably on the low side, as in low population density areas the ratio of gas stations to restaurants is surely higher.

If I were going to do it by town, I'd argue that with 16,000 people we have 12 gas stations. So 300M people need around 230,000.

18. Dec 5, 2011

### -Dragoon-

I'd love to do conceptual questions from the book as much as the numerical ones, but the author hasn't provided answers (to even the odd numbered questions). The only way to know the answer is to either go to office hours, which at most will get me through 2 conceptual questions per visit unless I decide to rush my professor, which is rude.

19. Dec 6, 2011

### Nano-Passion

That isn't too surprising, I had a feeling my estimates were a really bad average. It would have helped if I was able to look up a couple numbers to guide my estimate. =D

Use cramster.

20. Dec 6, 2011

### chiro

Conceptual understanding is really important especially if you want to apply something in a new context and I imagine many people including engineers, scientists, and mathematicians will probably have to do this at some point.

In terms of conceptual understanding, it is probably a good idea to look at things in terms of assumptions, representation, and constraints. If you know the assumptions, you know the constraints and that will help you deal with figuring something out that has more relaxed constraints, or completely different constraints. The representation is also important because you may deal with systems in say a cartesian coordinate system or a polar coordinate system and if you aren't in the right system and you don't know what is really going on, then you're bound to run into trouble.

So I guess my advice in closing to you, would be to at least recognize the constraints and aspects related to the representation, and that will help you both with calculating stuff and with coming up with something new when you can't use what already exists.