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It's All About The Maths...DOH! by Boondawg
Started on: 11-01-2019 09:05 PM
Replies: 2 (110 views)
Last post by: Boondawg on 11-02-2019 11:26 AM
Boondawg
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Report this Post11-01-2019 09:05 PM Click Here to See the Profile for BoondawgSend a Private Message to BoondawgEdit/Delete MessageReply w/QuoteDirect Link to This Post
Found on Reddit:

 
quote
Is this really true?



The first response:

 
quote
Lessee...

According to my micrometer, and my son's halloween candy, a DumDum is an oblate sphereoid 17mm in axial diameter and 17.5mm in equatorial diameter, with a ring 20.25mm in outer diameter and 4mm thick. The stick penetrates 13.5mm in and is 3.2mm in diameter.

So.

V = Sphereoid(d1: 17.5mm, d2: 17.5mm, d3: 17mm)
+ Ring(id=17.5mm, od=20.25mm, t=4mm)
- Cylinder(d=3.2mm, h=13.5mm)
where

Sphereoid: (d1, d2, d3) = π × d1 × d2 × d3 / 6
Ring: (id, od, t) = t × π × (od² - id²) / 4
Cylinder: (d, h) = h × π × d² / 4
That comes out to 2943.5 mm³, or ~2.94 cc (measurements on candy aren't that precise anyway; the micrometer's calipers dig into it).

Uranium has a density of 19.1 g/cc, so that's 56.22 g of U-235.

An atom of U-235 masses 235 amu, and converts to 211.3 MeV of energy, 8.8 MeV of which are lost as neutrinos, leaving 202.5 MeV available as usable energy*. 202.5 MeV / 236 amu (you include the neutron in the mass) comes out to an idealized maxium energy density of 22.997 MWh/g, ignoring efficiency.

That makes the lollipop have a potential energy of 1.29 GWh.

The U.S. consumes a total of 101.3 quadrillion Btu in 2018, which is 29,688,000 GWh. Per capita, that comes out to 90.7 MWh / year, and the sucker would last just a bit over 14 years.

If they meant "electricity" where they use "energy", the U.S. consumed 4,178 million MWh in 2018, which is 12.77 MWh / year per capita. The lollipop would last said American for just over 101 years for just electricity.

Either way, it's off - but for a physicist's "right order of magnitude" ballpark for back of the envelope calcs, it ain't bad.

For the last part, coal emits 820 g CO2 / kWh, which makes that 1.29 GWh equivalent to ~1,057 tonnes of CO2.


*It starts out as the kinetic energy of alpha and beta particles, as well as the energy of gamma photons. In a reactor, these all shake out into heat. The neutrinos fly off through the earth and into space as a signal to other civilizations that we're doing something pretty interesting.


"Someday MATH will save your life!" ~ Every Teacher Ever

P.S. I like my new ratings status!
Hmmm, I wonder what I did wrong?
What "rule" I broke.

Unless...wait, is this about toeing the line?
Disagreement?
Silly.

[This message has been edited by Boondawg (edited 11-01-2019).]

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Lambo nut
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Report this Post11-02-2019 09:27 AM Click Here to See the Profile for Lambo nutSend a Private Message to Lambo nutEdit/Delete MessageReply w/QuoteDirect Link to This Post
One sucker = one trip in the Delorean with change.
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Boondawg
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Report this Post11-02-2019 11:26 AM Click Here to See the Profile for BoondawgSend a Private Message to BoondawgEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Lambo nut:

One sucker = one trip in the Delorean with change.


Lol!
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