## Fermi Questions C

Entomology
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### Fermi Questions C

Seeing as SoCal has replaced Game On with Fermi Questions, I thought I would open a thread to further study for this event. Can a mod make it a topic in the study event forum too or...?

Anyone with any advice? (I'm looking at you, samlan) I looked at the wiki page and this seems like a...mathematical event.
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[NerdyTotoro]
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### Re: Fermi Questions C

Seeing as SoCal has replaced Game On with Fermi Questions, I thought I would open a thread to further study for this event. Can a mod make it a topic in the study event forum too or...?

Anyone with any advice? (I'm looking at you, samlan) I looked at the wiki page and this seems like a...mathematical event.
samlan16 is gone though?

appleshake123
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### Re: Fermi Questions C

For help, being knowledgeable on unit conversion and measurements of many things. Also, I was told when estimating, .5-5=10^0, 5-50=10^1 50-500 = 10^2 etc. "Fermi estimates generally work because the estimations of the individual terms are often close to correct, and overestimates and underestimates help cancel each other out."

From what I know of this event, it is quick estimation knowing many conversions and answering using the power of 10. An example from a test this year is, "How many unsharpened pencils would fit between the centre of the milky way and the Sun?" (Example answer: 10^1 = 1, 10^30= 30)

The milky way is about 30kpc wide, Sun is not on the centre, so the distance is probably around 12kpc so 1E4 pc.
A parsec is 3.26 light years(time light travels in a year) 3E0
A day is 86400, or abour 9e5 seconds, so a year is about 9e5*300 or 3E7 s
Light is 3*10^8 m/s or 3E8 m
So a light year is 9E15 meters, about E16
Let's say a pencil is 1/5 a metre, so 5 is E1
E4 pc* E0 ly/pc * E16 m/ly * e1 pencils/ m = E(4+0+16+1)= FA= 21
Actual answer from internet: Distance from milky way to sun is 8kpc which is 9.719e+21 inches. an unsharpened pencil is 7.5 inches, so there are about 1.3 e21 pencils from milky way to sun, so FA= 21 is correct.
Another question! What is the surface area of water on earth in yellow school busses?

jonboyage
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### Re: Fermi Questions C

For help, being knowledgeable on unit conversion and measurements of many things. Also, I was told when estimating, .5-5=10^0, 5-50=10^1 50-500 = 10^2 etc. "Fermi estimates generally work because the estimations of the individual terms are often close to correct, and overestimates and underestimates help cancel each other out."

From what I know of this event, it is quick estimation knowing many conversions and answering using the power of 10. An example from a test this year is, "How many unsharpened pencils would fit between the centre of the milky way and the Sun?" (Example answer: 10^1 = 1, 10^30= 30)

The milky way is about 30kpc wide, Sun is not on the centre, so the distance is probably around 12kpc so 1E4 pc.
A parsec is 3.26 light years(time light travels in a year) 3E0
A day is 86400, or abour 9e5 seconds, so a year is about 9e5*300 or 3E7 s
Light is 3*10^8 m/s or 3E8 m
So a light year is 9E15 meters, about E16
Let's say a pencil is 1/5 a metre, so 5 is E1
E4 pc* E0 ly/pc * E16 m/ly * e1 pencils/ m = E(4+0+16+1)= FA= 21
Actual answer from internet: Distance from milky way to sun is 8kpc which is 9.719e+21 inches. an unsharpened pencil is 7.5 inches, so there are about 1.3 e21 pencils from milky way to sun, so FA= 21 is correct.
Another question! What is the surface area of water on earth in yellow school busses?
When you say yellow school buses, are you referring to one side of a school bus, or the total surface area of a bus if you were to "unfold" it?

Unome
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### Re: Fermi Questions C

For help, being knowledgeable on unit conversion and measurements of many things. Also, I was told when estimating, .5-5=10^0, 5-50=10^1 50-500 = 10^2 etc. "Fermi estimates generally work because the estimations of the individual terms are often close to correct, and overestimates and underestimates help cancel each other out."

From what I know of this event, it is quick estimation knowing many conversions and answering using the power of 10. An example from a test this year is, "How many unsharpened pencils would fit between the centre of the milky way and the Sun?" (Example answer: 10^1 = 1, 10^30= 30)

The milky way is about 30kpc wide, Sun is not on the centre, so the distance is probably around 12kpc so 1E4 pc.
A parsec is 3.26 light years(time light travels in a year) 3E0
A day is 86400, or abour 9e5 seconds, so a year is about 9e5*300 or 3E7 s
Light is 3*10^8 m/s or 3E8 m
So a light year is 9E15 meters, about E16
Let's say a pencil is 1/5 a metre, so 5 is E1
E4 pc* E0 ly/pc * E16 m/ly * e1 pencils/ m = E(4+0+16+1)= FA= 21
Actual answer from internet: Distance from milky way to sun is 8kpc which is 9.719e+21 inches. an unsharpened pencil is 7.5 inches, so there are about 1.3 e21 pencils from milky way to sun, so FA= 21 is correct.
Another question! What is the surface area of water on earth in yellow school busses?
Most likely you mean the top; either way, the difference is probably ~E0.5 or so, in which case the lower number is safer, since I don't know for sure.

Earth radius is around 6000 km
Surface area of earth is around 6000^3 times pi times 4/3 which is around E8
Times 70% which should about bring down the extra from 6^3
Convert to meters so E14
Top of a school bus is around 2 meters by 10 meters, so 2E1
E14/2E1
Question: If you accelerated a bullet to 0.01% of the speed of light, how far would it penetrate into a solid wall of arbitrary thickness composed of Kevlar? (assuming that the wall is securely anchored).

appleshake123
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### Re: Fermi Questions C

Question: If you accelerated a bullet to 0.01% of the speed of light, how far would it penetrate into a solid wall of arbitrary thickness composed of Kevlar? (assuming that the wall is securely anchored).
I'm trying
How many electrons are there in the universe?

Unome
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### Re: Fermi Questions C

Assuming you mean the observable universe, since the amount of matter in the universe is generally accepted to be infinite
From the internet
If there was a planet with the same mass as Earth, with a diameter such that the Earth could be inscribed in a rectangular prism, which was itself inscribed in this hypothetical planet, what would be the density of this planet in kilograms per cubic meter?

appleshake123
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### Re: Fermi Questions C

Assuming you mean the observable universe, since the amount of matter in the universe is generally accepted to be infinite
From the internet
If there was a planet with the same mass as Earth, with a diameter such that the Earth could be inscribed in a rectangular prism, which was itself inscribed in this hypothetical planet, what would be the density of this planet in kilograms per cubic meter?
Assuming the earth is a perfect sphere
From the internet
Within the average high schooler's sleep during the school year, how many periods of radiation of a Cs-133 atom moving between two hyperfine level of the ground state occurs? I probably worded this poorly.

Unome
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### Re: Fermi Questions C

This is from atomic clocks right?
From the internet
How many blades of grass are there over all land area on the Earth classified as grasslands? (idk I couldn't think of anything good)

jonboyage
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### Re: Fermi Questions C

Internet
What is the length of all of the atoms in a single average person's body lined up in a single atom-wide line in terms of Milky-Way-radii?

Unome
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### Re: Fermi Questions C

Nice units
From the Internet
Over the course of one year, how many skin cells will be produced on a single adult human?

appleshake123
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### Re: Fermi Questions C

Nice units
From the Internet
Over the course of one year, how many skin cells will be produced on a single adult human?
Many die
Since I'm unoriginal, what is 262! [EDIT: Brute force got it even if doubles arent large enough]

raxu
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### Re: Fermi Questions C

Many die
Since I'm unoriginal, what is 262! [EDIT: Brute force got it even if doubles arent large enough]
Let's See how I do
In chains (the Imperial Unit), how wide is an Iridium atom?
Richard
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Unome
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### Re: Fermi Questions C

Restarting this in preparation for Fermi I'm return next year.
Starting with a semi-introductory level question: How many steps could an average person walk in 100 days, assuming no rest and a constant brisk pace?
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Raleway
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### Re: Fermi Questions C

Restarting this in preparation for Fermi I'm return next year.
Starting with a semi-introductory level question: How many steps could an average person walk in 100 days, assuming no rest and a constant brisk pace?
What's hiding lol