## Fermi Questions C

NeilMehta
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### Re: Fermi Questions C

So I posted the question above, and here is another question for visibility!

question 1: how many pacific oceans are needed to fill a school bus?
Question 2: how many potatoes would i have to eat to get to Vega walking ?
I'm leaving the second one open for someone, but here's my answer for the first The pacific ocean has about E15 meters squared of water iirc (probably wrong)
A schoolbus can hold 2mx8mx2m of water, so E2
Would that be E-13??
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talkingturtle101
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### Re: Fermi Questions C

Question 2: how many potatoes would i have to eat to get to Vega walking ?
```- I don't know how far away Vega is, but i'll say it's 50 light-years away.
- A light year is around 10^13 km, or 10^16 meters, so Vega is 5*10^17 meters away.
- A potato could maybe give someone 100 calories.
- A normal person needs 2,000 calories and walks 15,000 steps. This is 0.12 calories per step, about.
- A step is about 1 meter.
- A potato could then give 750 steps.
- 5*10^17 divided by 7.5*10^2 rounds to a Fermi Answer of 15.```
```- Vega is 25 light-years away
- A light year is 10^16 meters, so Vega is 2.5*10^17 meters away.
- A normal potato is 163 calories.
- For every 20 steps, you burn 1 calorie, or 0.05 calories per step, so we assume you need 0.05 calories to take a step.
- A normal stride is 0.76 meters
- A potato could give you 3,260 steps.
- A potato could therefore give you 2477.6 meters
- 2.5e17 divided by this is almost exactly 10^14 potatoes, so Fermi Answer of 14.```
Every fall, how many leaves are dropped by all trees across the U.S.?
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2017-18 Events: Astro, Chem Lab, Fermi Questions, Microbe

Unome
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### Re: Fermi Questions C

```- (Under)estimating E3 leaves dropped per tree per year
- Estimating E8 trees in the US (I (hope I) remember this from another problem about U.S. trees)
- So E11 leaves dropped
```- 2.28E10 trees in the U.S. There's probably a lot of deciduous trees, in the range of 1.5E10 from what I can figure out.
- There appears to be a little under E5 leaves on the average deciduous tree
So around E15
A part of the event that hasn't been covered yet in this thread (unless I'm remembering wrong):

How far away is the Earth from the sun, measured in units of blue whales laid end to end?
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### Re: Fermi Questions C

```- (Under)estimating E3 leaves dropped per tree per year
- Estimating E8 trees in the US (I (hope I) remember this from another problem about U.S. trees)
- So E11 leaves dropped
```- 2.28E10 trees in the U.S. There's probably a lot of deciduous trees, in the range of 1.5E10 from what I can figure out.
- There appears to be a little under E5 leaves on the average deciduous tree
So around E15
A part of the event that hasn't been covered yet in this thread (unless I'm remembering wrong):

How far away is the Earth from the sun, measured in units of blue whales laid end to end?
```The distance from the Earth to the Sun is 1.496E11 meters. Exponent of 11
Blue whales are ~30 meters. Exponent of 1
Dividing gives a Fermi Answer of 10```
`[url=https://www.wolframalpha.com/input/?i=(1+AU)%2F(length+of+a+blue+whale)]Wolfram Alpha[/url] gives an answer of 4.7E9 to 6E9`
`How many atoms are in the human body?`
Last edited by Adi1008 on June 24th, 2017, 9:53 pm, edited 1 time in total.
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Unome
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### Re: Fermi Questions C

```- Hydrogen is dominant (75%
mole fraction, 20% mass).
- Taking a 70 kg human, that's 1.4E4 grams of hydrogen, which is 1.4E4 moles.
- Using Avogadro's number, that's around E28 atoms.
```Google says 7E27.
How long would it take for the volume of the Pacific Ocean to flow through a standard kitchen sink?
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talkingturtle101
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### Re: Fermi Questions C

```- The Pacific probably has E18 liters of water
- A sink could probably dispense 1 liter every ten seconds.
- Multiplying gives us E19 seconds, Fermi Answer of 19.```
```- The Pacific actually has a volume of 660,000,000 km^3, and 1 km^3 is E12 liters.
- This gives a volume of 6.6E20.
- I think the one liter per ten seconds thing is accurate.
- This gives us 6.6E21, Fermi Answer of 22.```
Assuming you had all the wood and metal, how many violin bows could be made using the tails of all the horses in the world?
Mounds View HS, MN

2017-18 Events: Astro, Chem Lab, Fermi Questions, Microbe

Ashernoel
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### Re: Fermi Questions C

```- The Pacific probably has E18 liters of water
- A sink could probably dispense 1 liter every ten seconds.
- Multiplying gives us E19 seconds, Fermi Answer of 19.```
```- The Pacific actually has a volume of 660,000,000 km^3, and 1 km^3 is E12 liters.
- This gives a volume of 6.6E20.
- I think the one liter per ten seconds thing is accurate.
- This gives us 6.6E21, Fermi Answer of 22.```
Assuming you had all the wood and metal, how many violin bows could be made using the tails of all the horses in the world?
Isn't the volume of the Pacific Ocean FA9? From google
NT '19
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### Re: Fermi Questions C

```- The Pacific probably has E18 liters of water
- A sink could probably dispense 1 liter every ten seconds.
- Multiplying gives us E19 seconds, Fermi Answer of 19.```
```- The Pacific actually has a volume of 660,000,000 km^3, and 1 km^3 is E12 liters.
- This gives a volume of 6.6E20.
- I think the one liter per ten seconds thing is accurate.
- This gives us 6.6E21, Fermi Answer of 22.```
Assuming you had all the wood and metal, how many violin bows could be made using the tails of all the horses in the world?
Isn't the volume of the Pacific Ocean FA9? From google
I think that's in km^3, while talkingturtle101 converted to liters.
University of Texas at Austin '22
Seven Lakes High School '18
Beckendorff Junior High '14

Ashernoel
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### Re: Fermi Questions C

```- The Pacific probably has E18 liters of water
- A sink could probably dispense 1 liter every ten seconds.
- Multiplying gives us E19 seconds, Fermi Answer of 19.```
```- The Pacific actually has a volume of 660,000,000 km^3, and 1 km^3 is E12 liters.
- This gives a volume of 6.6E20.
- I think the one liter per ten seconds thing is accurate.
- This gives us 6.6E21, Fermi Answer of 22.```
Assuming you had all the wood and metal, how many violin bows could be made using the tails of all the horses in the world?
Isn't the volume of the Pacific Ocean FA9? From google
I think that's in km^3, while talkingturtle101 converted to liters.
Ohhh in the actual event would we memorize most of these common values if we wanted to be competitive at it?
NT '19
Harvard '23

talkingturtle101
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### Re: Fermi Questions C

You could either memorize them or know enough to reasonably estimate.
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2017-18 Events: Astro, Chem Lab, Fermi Questions, Microbe