Stupid Questions

[Datepalm]

M = (174.7 * 10⁶ km) * (33.5 km/s)² / 6.674 * 10⁻¹¹ m³ kg⁻¹ s⁻²

M = (174.7 * 10⁶ km) * (33.5 km/s)² / 6.674 * 10⁻²⁰ km³ kg⁻¹ s⁻²

M = 174.7 kg * 10²⁶ * 33.5² / 6.674

M = 2.94 * 10³⁰kg

This is where my real misunderstanding was, I think. (aside from the G. Honest, thats what it says. Bottom of the last page)

I got sidetracked from Errant Bards explanation on the G think and have only just realized that converting km^2 into m^2 means a grid of a thousand m^2 by a thousand m^2 - so a million meters (and not a line of a thousand meters) or a jump of 10^6 and not 10^3, and m^3 being a cube a 1000 on a side, so a million times a thousand cube-meters so 10^9.

Does this hold for g/kg? I can't visualize a cubic kilogram differently from a regular one, can I? :huh:

[Happy Ent]

Ah, the pleasures of being a formalist! I don’t visualise anything. It’s just symbols to me, with no semantics.

[Altherion]

(aside from the G. Honest, thats what it says. Bottom of the last page)

Tell them to correct it so that other people don't waste their time trying to figure out why their units don't work. I'm kind of curious how they made this mistake: they not only got the powers wrong, but they got it wrong on all three fundamental units.

Does this hold for g/kg? I can't visualize a cubic kilogram differently from a regular one, can I? :huh:

Yes. However, unless you're good at visualizing geometry in 4 or more dimensions, at some point it is easier to use algebra. In your example:

kg³ = (1000g)³ = 10⁹g³

[Datepalm]

kg³ = (1000g)³ = 10⁹g³

Yay, I get it now! K just means '1000' anyway. If you're a roman, I suppose.

ETA - although, I can visualize the k high/wide/deep cube existing in k points in time for

km⁴=(1000m)⁴=10¹² m³

hopefully after that i'll just remember the algebra:P

[Happy Ent]

Yay, I get it now! K just means '1000' anyway.

Better yet, “k is an abbreviation for *10³” (including the multiplication sign is crucial, and the exponential notation “scales better”). This way, it’s a purely syntactic transformation

(4 kilofortnight)² = (4 * 10³ fortnights)² = 4² (10³)² fortnight²= 4² (10⁶) fortnight²

or sixteen million squared fortnights.

Now, for exercise, express this in the proper SI unit, squared seconds.

[Datepalm]

Better yet, "k is an abbreviation for *10³" (including the multiplication sign is crucial, and the exponential notation "scales better"). This way, it's a purely syntactic transformation

(4 kilofortnight)² = (4 * 10³ fortnights)² = 4² (10³)² fortnight²= 4² (10⁶) fortnight²

or sixteen million squared fortnights.

Now, for exercise, express this in the proper SI unit, squared seconds.

16^6*1,209,600^2 sec^2 in a square fortnight?

[Maltaran]

Rounding to 3 significant figures, I get 2.34 * 10^19 s^2 = 16 million square fortnights

[Happy Ent]

Does this hold for g/kg? I can't visualize a cubic kilogram differently from a regular one, can I? :huh:

xkcd 775

[Datepalm]

xkcd 775

I thought women were supposed to be the none-spacially-visualizing capable ones? Dammit, I need some consistency in the gender stereotypes I recieve from the enviorment, or how will I know when to simper.

[Black Wizard]

Really stupid maths question:

when trying to do something with G (6.67*10^-11 m/kg^2/s^3) what am I supposed to do with the m/kg/s^2? Every explanation I can find just shows whatever formula and cheerily goes "now plug in the numbers and heres the answer",( which is never my answer), skipping over the how the calculation actually goes.:dunno:

eta for correct (I think) G

This looks suspiciously like Physics to me, which is not the same as Mathematics!

Maybe, but if there is, your freezer at home probably can't get there. Your typical home freezer is probably at around -20 C. In contrast, cryopreservation of bacteria at temperatures between -196°C and -150°C (in or above liquid nitrogen) is a common and reliable method for long-term storage.

Wow. :o

[Mme Erzulie]

Ok, here's a question:

The last times I've been out flying, the aircraft personnel have prevented the passengers from using certain rows, as they claim it will adversely affect "the balance and weight of the plane". The first time, the plane was half empty, so I thought fair enough and didn't think much more of it. But when I flew again today, there was only two rows, row 3 & 4, that were off-limits. And again with the same explanation.

Is there any sort of truth to this explanation? Or is it just something they tell us to stop asking questions about why no one can sit there, and the real answer is it's easier for the stewards if everyone is sitting together? Or is it a ploy to make sure that people who have only paid for one seat will not be allowed to spread out over two or three (gasp!) seats? This is Ryanair we're talking about, by the way. My knees hate them.

[Ski the Swift]

If I'm leaving from Sydney on the 26th of December at 10am flying to San fransico then from there to Columbus Ohio, will I arrive on Christmas day?

[Datepalm]

If I'm leaving from Sydney on the 26th of December at 10am flying to San fransico then from there to Columbus Ohio, will I arrive on Christmas day?

Sydney is 18 hours ahead of SF, so if you leave at 10am on the 26th Sydney time its already 4pm on the 25th in SF, so the flight needs to last less than 8 hours, which sounds a bit too short to me, especially if you have another couple of hours flight time + a couple of timezones to Colombus. If you were to leave at 1am though I think its possible.

[TerraPrime]

Maybe, but if there is, your freezer at home probably can't get there. Your typical home freezer is probably at around -20 C. In contrast, cryopreservation of bacteria at temperatures between -196°C and -150°C (in or above liquid nitrogen) is a common and reliable method for long-term storage.

Allow me to add to that.

Some bacteria withstand freezing better than others. For instance, E. coli O157:H7 survives freezing quite well, whereas Campylobacter jejuni is a wimp when it comes to cold.

But given the same species/strain of bacteria, different freezing condition also makes a difference. We routinely keep stocks of bacteria at -70oC. However, if you just chuck the bacteria in their growth medium into that temperature, you will not get a very efficient freezing, meaning probably 90% of what you tried to freeze will die. If you were to change out their growth medium and add some glycerol (10%), and then freeze them in an ethanol-dry ice bath, then you can minimize the loss you incur from the freezing to less than 5%.

In general, freezing food at home is not a reliable way of controlling microbial content of the food.

[Altherion]

The last times I've been out flying, the aircraft personnel have prevented the passengers from using certain rows, as they claim it will adversely affect "the balance and weight of the plane". The first time, the plane was half empty, so I thought fair enough and didn't think much more of it. But when I flew again today, there was only two rows, row 3 & 4, that were off-limits. And again with the same explanation.

Is there any sort of truth to this explanation?

The part about weight is an obvious lie -- where the passengers sit can never affect the weight of the plane. Think about marbles in a large box: as long as you don't take any out, moving them around within the box will not change the weight of the box.

The part about balance is almost certainly a lie. First, commercial aircraft weigh tens to hundreds of tons when empty while human beings weigh on the order of 0.1 tons so unless you are talking a really small and light plane, where the passengers sit will not make a difference. Second, even on the latter you would have to do something pathological (e.g. have every passenger sit on the right side of the aisle) for it to count -- there is no way to make a couple of rows have any effect whatsoever. It's physically impossible with rows in the middle and would take a really badly designed airplane even with the rows at the edge.

Long story short: they're lying to you.

[Warg Arry]

The part about weight is an obvious lie -- where the passengers sit can never affect the weight of the plane. Think about marbles in a large box: as long as you don't take any out, moving them around within the box will not change the weight of the box.

The part about balance is almost certainly a lie. First, commercial aircraft weigh tens to hundreds of tons when empty while human beings weigh on the order of 0.1 tons so unless you are talking a really small and light plane, where the passengers sit will not make a difference. Second, even on the latter you would have to do something pathological (e.g. have every passenger sit on the right side of the aisle) for it to count -- there is no way to make a couple of rows have any effect whatsoever. It's physically impossible with rows in the middle and would take a really badly designed airplane even with the rows at the edge.

Long story short: they're lying to you.

Do they not expect any intelligent people to fly with them?

[Black Wizard]

Why do old people shop in Marks & Spencers? They can't afford to keep their heating on over winter but they can afford to do their shopping in an upmarket department store. It connfuses the hell out of me when I see a working class Dundee Wifie picking up a curry and then putting it straight back down again - she's probably never eaten a curry in her life! It strikes me as something of a paradox.

[Stalker]

Why do old people shop in Marks & Spencers? They can't afford to keep their heating on over winter but they can afford to do their shopping in an upmarket department store. It connfuses the hell out of me when I see a working class Dundee Wifie picking up a curry and then putting it straight back down again - she's probably never eaten a curry in her life! It strikes me as something of a paradox.

I'm sure you've heard the term 'Keeping up appearances'.

[litechick]

OK, I've got a couple.

1) How do you restore your PC desktop to the default picture? I changed it and don't like it but I can't find the original in order to put it back.

2) My business insurance company keeps sending me these URGENT! requests that I sign over my voting rights to a proxy for voting at the annual meeting in another state. They don't say what are the issues being decided.

My initial reaction is that No, you cannot vote in my name without telling me what's being voted on. Maybe I am being ignorant about insurance though so if anybody knows of a good reason why I should agree to this, please let me know.

3) Is there any way to make my ipod play just one episode of a podcast and then turn off? I like to go to sleep listening to This American Life sometimes but there's no sleep timer and it just keeps playing all night.

(eta number 3)

[Sis Who Swears]

What's with the various foreign language typefaces in people's usernames, and is everyone eventually going to back to normal?

I have a stupid question related to this... I can't figure out how to get FF to enable them. :dunce: