Why does it fail?

Discussion in 'Science' started by HereWeGoAgain, Dec 4, 2019.

  1. HereWeGoAgain

    HereWeGoAgain Banned

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    Why? How?
     
  2. Derideo_Te

    Derideo_Te Well-Known Member

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    The ISS (and everything on board) is "falling" back into Earth's gravity but at a relative speed that keeps it in orbit around the Earth. That orbit only exists because of Earth's gravity and it is not any different to what keeps the Moon in orbit.

    I recall that this was explained to the original NASA astronauts by taking them out to the desert and getting them to drive around in circles from a fixed center point at greater distances.
     
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  3. HereWeGoAgain

    HereWeGoAgain Banned

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    Yes, they fall towards the earth at the same rate that the earth moves away from them, as they move forward. So they are in constant free fall!

    When the centripetal force of their motion - Mass x velocity^2 divided by the orbital distance from the center of the earth, R, - is equal to the force of gravity,
    Mstation x Velocity^2 / R = Mearth x Mstation x G/R^2

    This true when V^2 = Mearth G/R

    G is the gravitational constant.
     
    Last edited: Dec 20, 2019
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  4. yguy

    yguy Well-Known Member

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    More accurately, 2LTD has been addressed to death in this thread, so I saw no need to mess with it.

    As a side note, I don't know that 2LTD matches observations as well as Newton's Law of Gravitation does.
     
  5. HereWeGoAgain

    HereWeGoAgain Banned

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    Sure sure sure ;)
     
  6. Thehumankind

    Thehumankind Well-Known Member

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    Friction loses as well as electrical winding resistances.
     
  7. HereWeGoAgain

    HereWeGoAgain Banned

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    This is one of my favorites from physics.

    Most science-minded people know that when current flows in a wire, it creates a magnetic field around that wire. Current in a wire is a measure of the flow of charge in that wire. If we stand at one spot next to the wire, electrons are flowing past us with some average velocity, which as it turns out is surprisingly slow.

    We know from Relativity that uniform motion is relative. In other words, are the electrons moving past us, or are we moving past the electrons? An electron might say we are in motion, not it. In order to test this, we can replace the wire with an electrically charged metal sphere. We can view this as one giant electron sitting in our lab. Now, if we run past the metal sphere, we see the giant electron moving past us. Since we see a charge in motion, we measure a magnetic field. If we stop running, the magnetic field magically disappears.

    Whether the charge moves past us, or we run past it, is irrelevant. If we see a charge in motion relative to us, we measure a magnetic field.

    So a magnetic field is simply an electrical field view relativistically - in motion relative to us.

    How cool is that?!?!
     
    Last edited: Dec 24, 2019
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  8. Robert E Allen

    Robert E Allen Banned

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    Never took physics in highschool. I don't think many did.
     
  9. HereWeGoAgain

    HereWeGoAgain Banned

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    I sort of flubbed the great reveal. That should have read, "a magnetic field is simply and electric field viewed relativistically". So what about permanent magnets? Where is the motion? The motion is in the orbits of the electrons around the nucleus of their respective atoms. What makes a magnet unique is that the orbits of the electrons are all aligned, and don't cancel each other out as happens in non-magnets.

    And in regards to electricity, true or false? Electricity moves at the speed of light.

    Would anyone care to calculate the average speed of the electrons flowing at a rate of 10 amps, in a 10 gauge wire?
     
    Last edited: Dec 25, 2019
  10. Etbauer

    Etbauer Banned

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    How does a post which is answered by 'resistance and friction' push into 7 pages?
     
  11. Derideo_Te

    Derideo_Te Well-Known Member

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    Because there is a whole lot of "resistance and friction" to "pushing"!

    ;)
     
  12. Etbauer

    Etbauer Banned

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    lol, I'm not going to lie, I appreciate it, but I think it's a groan on that one.
     
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  13. Derideo_Te

    Derideo_Te Well-Known Member

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    Yup, but you opened yourself up for it! ;)
     
  14. Etbauer

    Etbauer Banned

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    don't we all.
     
  15. Derideo_Te

    Derideo_Te Well-Known Member

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    Yup!

    And I find it hard to resist sometimes!
     
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  16. HereWeGoAgain

    HereWeGoAgain Banned

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    There are many more questions. :rolleyes: You read one post and assumed that you know what is contained in the entire thread? Heck, there is another question just a one posts above yours. Jeeeezuz. Try reading a thread enough to get the context sometime.
     
    Last edited: Jan 4, 2020
  17. HereWeGoAgain

    HereWeGoAgain Banned

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    While it is often said that electricity travels at the speed of light, that isn't true. An electrical signal can travel at near the speed of light, typically about 0.5 C, but the electrons themselves travels very slowly. This is because the signal travels at the speed that a change in the source potential propagates through the electrons, much like the speed of sound is a measure of how fast a change in air pressure moves through the air; which is far faster than the air itself moves.

    The average velocity of electrons in a wire is called the drift velocity. It can be found by calculating how many electrons must flow past a point along the wire, in order to carry the required current.

    https://en.wikipedia.org/wiki/Drift_velocity

    So the electrons flowing in a wire having a diameter of 2 mm [12 gauge wire], and constituting 1 amp of current flow, are actually moving with an average speed of 0.000023 meters per second.
     
  18. HereWeGoAgain

    HereWeGoAgain Banned

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    How can we know when two events are truly simultaneous?
     

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