[Phys-L] Fermi question on state borders
Oh no, I made a mistake.
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We have made so many approximations that fussing over integrals and the
like is a waste of time. *I'm going to assume that, on average, you will
be **halfway from one side to the center. *
So, half of 450 km = 225 km.
*So my final answer is 200 km with a precision of one significant figure.*
How close am I?
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My erroneous calculation would be "to the center" not halfway. I needed to
divide by four, not two. So, again, just doing it all in my head, no
calculator allowed:
1/4 of 450 is about the same as 1/4 of 440 for a result of 110 km.
So my revised Fermi approximation answer is *110 km*.
Thank you Brian for the detailed response. If you now do your revision of
my result you get:
110 km / 1.59 = 69 km (although we don't have two significant figures of
precision). This result is a much closer match to Brian's original estimate
of 65 km. So perhaps you do not need to revise your earlier thinking at
all.
In the spirit of Fermi, I'm going to stick with 100 km.
John
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John E. Sohl, Ph.D.
WSU Brady Presidential Distinguished Professor Emeritus
Department of Physics and Astronomy
Department of Environmental Science
Department of Being Retired and Loving It
Weber State University
cell: (801) 476-0589 (Text me, I don't answer the phone if you are not in
my contacts.)