## Fermi Questions Marathon

iwonder
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### Re: Fermi Questions Marathon

Nice job with the question, but the point of the practice is that you don't use a calculator, since you can't use one in the event (now if you did that in some reasonable time without a calculator, I applaud you)

The Eviscerator
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### Re: Fermi Questions Marathon

DGing94 wrote:Central Park is about 1 mi^2. So for simplicity's sake we'll convert that to feet squared (1 mi^2)= (5280 ft* 5280ft)= 27,878,400 ft^2. If the grapevines are 5 feet apart they can be divided into sqaure units to make a grid within central park with each cell being 25 ft^2. So take (27,878,400/25) which gives you an answer of 1,115,136 cells. Assuming that the grapevines sit in the exact corners we can assume that 1 cell has all four grapevines and the rest have only two because two are already counted from a previous cell. So (1,115,135 * 2)= 2,230,270 + 4= 2,230,274. Giving an exponent of 6.

I'm a little new at this so let me try a question.
What is the molecular weight of water in an average 150lb man?
Well water is about 70% of a person's body weight. So it would just be .7(150)=100 lbs = E2

iwonder
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### Re: Fermi Questions Marathon

But it's asking for molecular weight of water, so I think the 'average human' part is just to throw you off. The molecular mass of water is 18g/mole, so 1 would be the answer? It's oddly phrased.
'If you're the smartest person in the room, you're in the wrong room' - Unknown

Schrodingerscat
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### Re: Fermi Questions Marathon

It appears there are currently no outstanding questions, so:

Two I would love to see solved my state test last year: (slight variations on them as I cannot remember exact wording)
What is the magnitude of the magnetic field 1 meter from an average tabletop lamp (Tesla)?
What is the magnitude of the electric field 1 meter from the same lamp (Volts per meter)?

Schrodingerscat
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### Re: Fermi Questions Marathon

Or what is the bandwidth of a standard car filled with audio cassette tapes driving between LA and NYC in bytes/second (assume driving full time)?

fourLoko
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### Re: Fermi Questions Marathon

Schrodingerscat wrote:It appears there are currently no outstanding questions, so:

Two I would love to see solved my state test last year: (slight variations on them as I cannot remember exact wording)
What is the magnitude of the magnetic field 1 meter from an average tabletop lamp (Tesla)?
What is the magnitude of the electric field 1 meter from the same lamp (Volts per meter)?
For the first one:
B=(mu_o)*I/(2*pi*r) where mu_o is the permeability of free space ~4piE-7. Normal outlets are like E2 Volts and I guess I'll assume the resistance of the lamp is E2 which would lead to a current of E0.
So then we have (4piE-7)/(2pi*1) which is E-7 Tesla. I'm thinking it could be lower though. Any input?
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nomynameisnotkevin
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### Re: Fermi Questions Marathon

OldSpice wrote:
Here's a question taken from the Athen's Invite last year:
How many Barns are there in an Attometer?
Surely, the Barn you speak of is not an actual barn that a farm would have, right?

fourLoko
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### Re: Fermi Questions Marathon

http://www.princeton.edu/~achaney/tmve/ ... unit).html

Pretty obscure and there's no way you'd get close to the answer without knowing it off the top of your head, which makes for a bad fermi question imo
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