Physics

[AzAtty]

I wanted to bump this old thread from last year for myself and all the other DMTs who are currently struggling with anxiety over the Physics exam.

This thread rocks and there's tons of good info on here, and it sounds like folks are more than happy to throw xtra practice questions at us if we ask very nicely.

(a) What is the displacement in fathoms of seawater of an unladen swallow?

(b) What is the displacement in fathoms of seawater of a swallow laden with a coconut?

(c) At what depth will the coconut carried by the swallow implode?

 

[scubasully]

The European swallow or the African swallow?


Ahhhhhhhhhhhhhhhhhhhhh!!!

 

[ClayJar]

(a) What is the displacement in fathoms of seawater of an unladen swallow?

(b) What is the displacement in fathoms of seawater of a swallow laden with a coconut?

(c) At what depth will the coconut carried by the swallow implode?

For questions (a) and (b), shouldn't that be *cubic* fathoms? (Looking at some quick numbers, a swallow laden with sufficient lead to completely submerge would displace about 40 cubic centifathoms, so I'll go with cubic centifathoms as my unit of choice.)

(a) 3 cubic centifathoms = 19 g / (1.025 g/cc) * (0.1635 cubic centifathoms/cc)

(b) 240 cubic centifathoms = 1.5 kg / 1.025 g/cc) * (0.1635 cubic centifathoms/cc)

Notes: That's the best I could come up with for mass of a coconut, and regardless, it would vary significantly. Also, given the expected mass of a coconut, the mass of the swallow is insignificant given the precision we're working with and can simply be ignored. Also, this assumes the coconut floats, which should certainly be the case if the husk is intact. I have not conducted buoyancy checks on coconut seeds without the husk.

(c) Insufficient data. (I would assume the question is now talking specifically about the husked seeds which are occasionally available at stores everywhere. It would be an interesting experiment, and I for one would welcome any attempt to develop such a data set. My expectation is that recreational depths would not cause an implosion, given the geometry and composition of the endocarp should be quite capable of sustaining significant compressive forces. On the other hand, the endocarp has been rather brittle in every specimen I have personally examined, so the implosion could be quite spectacular, albeit in a rather constrained manner. Caution is therefore called for so as to prevent potential injury to the experimenter.)

 

[AzAtty]

You should assume that the coconut has a husk of sufficient thickness that a swallow might securely grip it.

And -1 on both (a) and (b) because you didn't clarify whether the sparrow in question is an African or European swallow.

 

[Drew Sailbum]

All else aside, my #1 tip to anyone facing the physics exam is to do it in metric. Calculations seem to go so much smoother in metric.

 

[scubasully]

I'm thinking of going thru the exam when I get it and putting asterisks or something on the answer sheet for any question that is FRESHWATER, as that's where I consistently make mistakes while practicing. Also the flexible/inflexible container things might be messing me up, too (though that could be lack of understanding).

Any other tricks to avoid missing stupid stuff (besides doing it in metric)??

Thanks. :blinking:

 

[Web Monkey]

Tell that to Schrodinger's poor cat.

Is he (still?) dead (yet?)

Terry

 

[scubasully]

I just have to report that I've spent the entire day in bed with the flu, studying physics. I did the workbook chapter last night, got a bunch wrong, and then went through and highlighted the problem sections. I've been rereading the corresponding sections in the Encyclopedia, and then tackling those sections again. And sometimes I need to tackle them a 3rd time. However, I'm thoroughly enjoying working out the problems.

I am feeling pretty good about everything (except Henry's law right now). I feel like I have a pretty good understanding of things, but I can see how I could get easily tripped on a fsw question or a inflexible/flexible question, or one of the other questions that is sort of tricky for a non-scientist like me. For instance, I just spent 15 minutes trying to remember how to convert liters into bar, and then decided the answer must be D. Not enough info given. And I was right! Hooray. Just hope I can remember that during the exam. It's more likely I assume I've forgotten a formula.

I'm making a list of all the types of possible questions right now, along with the normal screw ups I encounter with each. It's fun. I'm feeling good. I'll report back when I've taken it. Hopefully I get a 75% at least, though I'm aiming for a 100%.

 

[Jim Lapenta]

What issue are you having with the law of solubility? Henry's law is not that difficult it is mainly remembering how pressure applies to bubble formation and getting rid of them. If I remember correctly back to my DM exams there really was not that much as far as actual details. What usually threw people was keeping all the gas laws straight. If you are having difficulty with that just remember that a great example of Henry's law is to open a can of coke. Want to simulate a too fast ascent? Shake the can and then open it!

 

[scubasully]

Henry's law is not that difficult it is mainly remembering how pressure applies to bubble formation and getting rid of them.

I have a wicked flu, so anything that involves thought is pretty difficult. I spent the day making up problems and plugging in numbers into gas law formulas. That was really doable for my pea soup state of mind. Reading and thinking and answering questions on concepts, not so much. It's just the flue, I suppose!