Re: Moon trials

Discussion in 'rec.sport.unicycling' started by Evan Byrne, Apr 10, 2005.

  1. U-Turn

    U-Turn Guest

    ObieOne's argument is only correct for short hops. In a hop, you are
    pushing up your center of mass. Tucking changes your shape so that
    your feet are closer to your center of mass. This tuck-distance is
    fixed by your body length and tuck skill, and does not change in the
    decreased gravity. However, your center of mass's hop height does change
    significantly when you are on the moon. So the 75% (the tuck's
    contribution to the overall hop height) drops way down.


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  2. well concerning the black tire/heat problem theres always the primo the
    wall tire in white which would reflect the heat. If this stuff is at all
    possible the unispin will look like childs play. Tricks would turn into
    bmx like spins and flips it would be about who ken get the most combos
    in. Instead of landing tricks people would be worried about finding more
    ways to stay up and add to combos of tricks that would be nutz. It would
    be kinda like riding on a non flexing trampoline with superbly strong
    legs. Of course all of this would prolly not be possible wearing normal
    space suits. It would probubly have to be indoors some how but that also
    might cancel out the null gravity effect, and also the frame of the uni
    would have to either be assembled on the moon (hard because no fire) or
    be made so that there are no completely sealed portions of the frame so
    that little portions of earths atmosphere were not taken with it because
    then wouldnt the frame explode because of the release of pressure. the
    tire would have to be made very forgiving so that it can expand and
    shrink to adjust to the atmosphere. but all in all that would be crazy
    if at all possible.


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  3. johnfoss

    johnfoss Guest

    burnitalltwice wrote:
    > *Instead of landing tricks people would be worried about finding more
    > ways to stay up and add to combos of tricks that would be nutz. *

    I can picture Julien Monny (in the gym of course; he never wears a
    shirt) doing handstand coasting, with his hands on the front and back of
    the seat.

    > *It would probubly have to be indoors some how but that also might
    > cancel out the null gravity effect, and also the frame of the uni
    > would have to either be assembled on the moon (hard because no fire) *

    If we build a gym on the moon, we'll bring some fire along. But there's
    no reason the vast majority of Earth unicycles will have a problem on
    the Moon except for being over-built. I only have one I'm aware of where
    the frame seals air in. On that one, if necessary, I could drill a
    little hole.

    Meanwhile, building a gym doe not affect your gravity unless you put it
    in orbit. That's another unicycling story entirely.


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  4. PhilS

    PhilS Guest


    > Having legs with 6x normal power, one would not have to extend his
    > legs as much before landing;



    actually, you would still hit the ground with the same force as on
    earth, seeing as you are 6x as high and 6x as fast.


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  5. Naomi

    Naomi Guest

    "maestro8" <[email protected]> wrote in
    message news:[email protected]
    >
    >
    > Consider also that your unicycle will weigh 1/6th of what it did on
    > earth... so when you do your massive moon hop, and you pull up on your
    > uni as hard as you would on earth, it will accelerate towards your
    > crotch 6x faster. Ouch! I hope that was a seat-out hop :)
    >



    Nope: force =mass x acceleration. not weight times acceleration:
    it WILL accelerate towards your crotch faster (not 6x faster) , but only
    because it is gaining less potential energy, leaving more of the energy you
    supply to accelerate the uni. and increase its kinetic energy ( the bit
    that hurts) .
     
  6. Naomi

    Naomi Guest

    "TheObieOne3226" <[email protected]>
    wrote in message
    news:[email protected].
    >
    >
    >
    > You wouldn't be able to hop 12 feet. 75% of hopping hieght is determined
    > by how much you pull the unicycle up, which isn't changed much by the
    > decreased gravity.
    >
    >

    Agreed! 3 or 4 feet might be a better guess for vertical hop

    Nao
     
  7. Naomi

    Naomi Guest

    "gerblefranklin" <[email protected]>
    wrote in message
    news:[email protected].
    >
    > Evan Byrne wrote:
    >> *i thought it was 2% of earths gravity *

    >
    >
    > Nope. Something missing from you understanding is that the force of
    > gravity followsx the inverse square law. This means that if gravity
    > pulls me with 40 lbs* from 10' from the edge of a round mass, it will
    > pull with 10lbs from 20's away.


    On the right lines but the distance is from the centre of gravity, not
    from the edge of a round mass :-0

    Yes me again!!!! Nao ;-)
     
  8. Naomi wrote:
    > *"gerblefranklin"
    > <[email protected]>
    > wrote in message
    > news:[email protected].
    > >
    > > Evan Byrne wrote:
    > >> *i thought it was 2% of earths gravity *

    > >
    > >
    > > Nope. Something missing from you understanding is that the force

    > of
    > > gravity followsx the inverse square law. This means that if

    > gravity
    > > pulls me with 40 lbs* from 10' from the edge of a round mass, it

    > will
    > > pull with 10lbs from 20's away.

    >
    > On the right lines but the distance is from the centre of gravity,
    > not
    > from the edge of a round mass :-0
    >
    > Yes me again!!!! Nao ;-) *



    No, not you again:p (well, we're both right, in a way...). Close, but
    no. There's a reason why Newton waited 20 years to publish his papers on
    gravity, even though he already had the equations figured out. The issue
    at hand was that in his papers he had simplified Earth's mass to a point
    source. He waited to verify if this was okay, and that 20 year interval
    was spent inventing integral calculus so that he could check it.

    You can't reduce all shapes of mass to a point source, so you are also
    wrong, in a way (yes, i was completely wrong on that one, but lets
    assume i was talking about doing sidehops off of small singularities, in
    which the center of mass is also the edge. We will ignore the infinitely
    blueshifted gamma radiation and extreme tidal forces). You can't
    simplify a barbell to a point source of gravity, even if you know the
    center of gravity. So we were both off.

    As for 3 or 4 feet, i don't see why we need to go to the moon for that.
    Zack B and Ryan A are already at 3.5', and riders as weak as me are
    approaching 3'.


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  9. Naomi

    Naomi Guest

    "gerblefranklin" <[email protected]>
    wrote in message
    news:[email protected].
    >
    > I don't see how the physics don't work out. Low gravity +
    > disproportionatly strong legs + low mass= gigantic hops, easy trials.
    > Precision might suffer a bit, but who cares? It's not like there's rail
    > gaps on the moon.
    >


    So many misconceptions and errors in this thread. I tried to resist the
    temptation to ignore them all, but have failed, so I will just pick a
    couple at random. Sorry gerblefranklin, but the random finger hit you
    first: And it will all probably help a few students with their coming
    GCSE's so I am going for it. ;-)

    Mass is unaffected by being moved to the moon, You meant low weight of
    course. I am sure you did.

    Nao
     
  10. Naomi

    Naomi Guest

    "gerblefranklin" <[email protected]>
    wrote in message
    news:[email protected].
    >
    > No, not you again:p (well, we're both right, in a way...). Close, but
    > no. There's a reason why Newton waited 20 years to publish his papers on
    > gravity, even though he already had the equations figured out. The issue
    > at hand was that in his papers he had simplified Earth's mass to a point
    > source. He waited to verify if this was okay, and that 20 year interval
    > was spent inventing integral calculus so that he could check it.
    >
    > You can't reduce all shapes of mass to a point source, so you are also
    > wrong, in a way (yes, i was completely wrong on that one, but lets


    Of course you cannot actually reduce shapes to a point source, I don't
    think I said that, but for a (1) uniform density object ( a simplification
    I did make) using the C of G point works for the calculation of gravity (
    and weight) at a defined distance. Calculus can fairly easily prove this.
    Newton may not have been able to initially prove it, but he was still
    correct. Certainly you cannot use the surface of the object from which to
    measure distance, or else at 20 feet above the earth we would have only 1/4
    the weight we have at 10 feet above it. bathroom scales would require
    calibration based on their height and you would weigh noticeably less stood
    on tiptoe. But you know all this of course.
    The problems of reducing a mass to a point source come once you start to
    rotate that object, at which time the mass distribution ( shape and size)
    becomes highly important
    (1) in the earth, local accumulations of heavy , or light ,rock do have a
    small effect on local values ( and direction ) of g, because the earth is a
    lump of material having a variable density. Such variation is, however,
    quite small.


    > As for 3 or 4 feet, i don't see why we need to go to the moon for that.
    > Zack B and Ryan A are already at 3.5', and riders as weak as me are
    > approaching 3'.
    >

    I didn't know people were up to 3.5 feet, I thought it was only around a
    couple, but the question remains, as another posrter pointed out: How
    much of that height is gained by lifting the uni up under you? That
    distance will not change by a factor of 6. There is no way you can multiply
    that 3.5 feet by 6 on the moon, because much of it is gained by another
    means than just the energy used in jumping. It is gained by
    redistributing your mass, by changing your shape.

    Nao
     
  11. maestro8

    maestro8 Guest

    Naomi wrote:
    > *Nope: force =mass x acceleration. not weight times acceleration:
    > it WILL accelerate towards your crotch faster (not 6x faster) , but
    > only because it is gaining less potential energy, leaving more of the
    > energy you supply to accelerate the uni. and increase its kinetic
    > energy ( the bit
    > that hurts). *



    Numbskull, that's what I said! I didn't misquote Newton's second law.
    And Gerble knows what he's talking about, too. We know our science;
    you're picking apart our nomenclature. Go fly a kite, you nitwit.


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  12. hobgoblin

    hobgoblin Guest

    Thats a bit harsh on Naomi, from a non-biased perspective, Naomi's posts
    make the most sense of any of you guys'.

    if your not going to get stupidly complex (anyone know the exact density
    map of the earth / moon?) then a sphere like the earth can be reduced to
    a point source at the centre from which gravity acts, and the inverse
    square law works from there. So youd have to move 6372km away to quarter
    your weight (not 10'), and I dont know ANYBODY who can hop that high.

    Also, its a misconception that anything with air in it will explode in a
    vacuum. By definition there is only 1 atmosphere (15psi) of pressure at
    sea level on earth and you put about 40psi in a tire (less for trials)
    which is 2.7 atmospheres. So the difference in pressure is about 1.7
    atmospheres (25 psi) and most tire/inertube combos can take like
    90psi.
    And since your gonna weigh less you wouldnt need so much pressure
    anyway.

    Drag is proportional to speed. And unicycles are not known for their
    speed, especially trials unis, so I dont expect that youd notice much
    difference between jumping in a vacuum and in air. So if youve put the
    effort into getting up there you may as well build an indoor trials
    arena (with a high roof and lots of oxygen supplies, and a bar, and an
    observation deck, space port, revolving restaurant, hotel, reasonably
    priced gift shop etc).


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  13. U-Turn

    U-Turn Guest

    If there is one thing Naomi is not, it's a nitwit.


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  14. bombsquad

    bombsquad Guest

    johnfoss wrote:
    > *
    >
    > Let's start with the Uni.com T-shirt scenario. An apollo Moon space
    > suit. Very heavy pack, and very restricted movement. I would venture
    > to say that you probably couldn't physically operate the unicycle in
    > one of those suits. So let's assume it allows a little more freedom of
    > movement, but still has a 70 pound (or so) pack on the back.
    > *




    I just couldn't resist this chance. This is a picture of me riding while
    in an EOD8 bomb suit. It is around 75+ pounds, minus the matching helmet
    which I am not wearing. I could manage around 30 or 40 feet at a time,
    so I am assuming that in a space suit which would probobly have around
    the same mobility and weight it would be possible to ride...


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  15. PopeSamXVI

    PopeSamXVI Guest

  16. maestro8

    maestro8 Guest

    bombsquad wrote:
    > *I just couldn't resist this chance. This is a picture of me riding
    > while in an EOD8 bomb suit.*



    We need a picture of you in the suit on the 'Surly 4\" Monster'
    (http://www.gb4mfg.com/temp/surly_monster/) with the helmet... riding
    down some stairs. Yeah.

    I'd buy the t-shirt _and_ the poster. Heck, I'd buy a few.


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  17. Klaas Bil

    Klaas Bil Guest

    Since kindly correcting seems to be the thing to do on this thread,
    here goes:

    On Thu, 14 Apr 2005 07:31:18 -0500, "hobgoblin" wrote:

    >Drag is proportional to speed.


    Drag is dependent on speed, but not proportionally. It's some higher
    power, the exponent of which is not constant and depends a.o. on
    Reynolds Number.

    >And unicycles are not known for their speed,


    Huh? When a unicycle is ridden, it has some speed per definition.
    People have discussed their speed on a unicycle at length. One might
    argue that unicycles are not known for 'high' speed, but that just
    depends on what you call 'high'. The speed on a Coker can be such that
    drag is a significant factor.

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  18. i have a feeling this thread is gunna b up 4 a while since 4 sum reason
    inteligence and unicyclist seem to be common


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  19. maestro8

    maestro8 Guest

    Klaas Bil wrote:
    > *Secondly, I dispute your implied definition of 'proportional'. To me,
    > in physics and mathematics 'proportional' is just shorthand for
    > 'directly proportional' (also known as 'linearly proportional').
    > *



    I will second this observation. If you're gonna write out an equation
    in shorthand (w/ variables) or longhand (in words) you better get your
    powers right. Ferchrissakes, if Coulomb's law wasn't proportional to
    1/r^2, we all wouldn't be here right now. Don't muck these things up!


    > -Originally posted by burnitalltwice-
    > *i have a feeling this thread is gunna b up 4 a while since 4 sum
    > reason inteligence and unicyclist seem to be a common combo
    > *



    Point and counterpoint all in one beautifully crafted run-on... :p


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