The physics behind the perfect size of a jet engine.
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The answer to this question has everything to do with drag & kinetic energy vs momentum change (thrust) – ie, a bigger engine fan allows for a larger air mass to be accelerated a smaller amount to give the same thrust as you’d get from a smaller engine with larger acceleration. Any acceleration of air imparts energy to that air, which is in principle wasted energy, so ideally we minimize the acceleration of air while maintaining constant thrust, aka bigger engine fan. However, bigger fans have more drag, so there is an ultimate size limit.
REFERENCES:
A350 schematics - http://www.aerospaceweb.org/aircraft/jetliner/a350/
747 schematics - http://www.aerospaceweb.org/aircraft/jetliner/b747/
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https://www.youtube.com/watch?v=ueTGjegTKoo
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This video is about the international system of units (SI), the international prototype kilogram (the IPK or "le grande k"), and specifically, why we need to redefine our base units in terms of fundamental constants - aka, concepts & ideas - rather than physical objects. The second is already defined in terms of a certain number of oscillations of a photon of the ground state hyperfine splitting energy of Cesium, the meter is then defined as how far light travels in a particular fraction of a second, and hopefully soon, the kilogram will be defined either using the Avogadro approach of counting silicon atoms in a sphere, or using the Watt (Kibble) Balance approach of measuring Planck's constant, h, as used in the formula E=hf for the energy of a photon, which relates to mass via Einstein's famous E=mc^2.
REFERENCES:
Most Recent Kilogram/Planck Constant Measurement: https://www.nist.gov/news-events/news/2017/06/new-measurement-will-help-redefine-international-unit-mass
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https://www.youtube.com/watch?v=VSrEIdhrXB4
The first video we created together with our friends at xkcd is out now! You can find it here: http://youtube.com/@xkcd_whatif
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https://www.youtube.com/watch?v=HS8MRzus7eU
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich
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https://www.youtube.com/watch?v=_bcfxty39Cw
What was the 2012 Nobel Prize in physics given for? Capturing a single photon of light!
Congrats to Serge Haroche and David Wineland
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
...
https://www.youtube.com/watch?v=2dRr-fnPCwM
You've heard of E=mc²... but you probably haven't heard the whole story.
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Music by Nathaniel Schroeder - http://www.soundcloud.com/drschroeder
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https://www.youtube.com/watch?v=NnMIhxWRGNw
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Volkswagen would like you to know that every new Volkswagen comes with no-charge scheduled maintenance for the first two years or 24,000 miles.
For more on time-travel, here are some works by physicist and time-lord Sean Carroll:
Rules for time-travellers - http://blogs.discovermagazine.com/cosmicvariance/2009/05/14/rules-for-time-travelers/#.UmQ5QBYz5Hw
Learn more about time and time-machines in his book From Eternity to Here - http://preposterousuniverse.com/eternitytohere/
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https://www.youtube.com/watch?v=FflcA85zcOM
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This video is about what would happen if we built a giant ring around earth – what would happen to the ring, that is. Would if fall? Collapse? Start spinning?
REFERENCES:
Why Isn’t It Faster to Fly West? Video https://www.youtube.com/watch?v=3gNkgj9h2oM
Physics Girl Quarter Shrinking: https://www.youtube.com/watch?v=d2TDXKfBaMQ
Symmetry Breaking: https://en.wikipedia.org/wiki/Symmetry_breaking
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https://www.youtube.com/watch?v=4xSPlQUejd8
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This video is about the "Kelvin wake" shape of water wakes behind boats - we talk about mach angle, dispersion, superposition of many waves, and how these all lead to the pattern of a wake. We don't get into Froude number though...
REFERENCES
Boat Wake Wikipedia Page: https://en.wikipedia.org/wiki/Wake
Interactive Boat Wake Simulation: https://observablehq.com/@rreusser/dispersion-in-water-surface-waves
Feynman Lectures on Water Waves: https://www.feynmanlectures.caltech.edu/I_51.html#Ch51-S4
Building up a Boat Wake from V-Shaped Wakes: https://editor.p5js.org/aatish/full/bDiykicsC
Wave Dispersion: https://en.wikipedia.org/wiki/Dispersion_relation
Mach angle shock waves:
https://www.sciencedirect.com/topics/engineering/mach-angle
Ship Wakes - Kelvin or Mach Angle? Rabaud and Moisy Paper: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.110.214503
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich
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https://www.youtube.com/watch?v=95sQcSulRFM