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Tell me why

  1. Apr 4, 2005 #1
    Tell me why....

    I have two simple physics questions that i can't figure out myself.
    1. How does cushion make a seat feel more comfortable?
    2. If a plane flies over a considerable distance, will there be a noticable flight time duration difference if it flies over the same distance from west to east direction against from east to west direction? I myself think that there will be a time difference since the earth rotates from west to east.
     
  2. jcsd
  3. Apr 4, 2005 #2

    chroot

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    It helps spread the force due to your weight more evenly over your butt.
    To a first approximation, the air on Earth rotates with the same velocity as the ground. Since the airplane maintains airspeed, in the absence of wind, there would be no difference in elapsed flight time in flying east versus flying west.

    Of course, the Earth really does have winds; an eastward wind would assist a plane when flying eastward, but hinder a plane when flying westward. A westward wind would have the opposite effect.

    - Warren
     
  4. Apr 4, 2005 #3
    Thanks a lot for the reply. I get it now
     
  5. Apr 4, 2005 #4

    Danger

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    There is one instance in which direction makes a difference, but it doesn't involve airspeed. Most space launches are conducted from as close to the equator as possible, in the direction of the Earth's rotation, because the large diameter there gives the highest rotational speed. This gives the rocket an assist toward reaching orbital or escape velocity, but it's relative to the space around the Earth, not another point on the Earth.
     
  6. Apr 4, 2005 #5
    Funny that this is in Physics, But a cushion helps because it contains trapped layers of air between the fibers. the more air, the softer the seat.
     
  7. Apr 4, 2005 #6

    chroot

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    hypatia,

    Regardless of the mechanism by which it is accomplished, the purpose of a cushion is to even out force.

    - Warren
     
  8. Apr 4, 2005 #7
    How does cushion make a seat feel more comfortable?



    But only a soft cushion makes it comfortable, I took his question to be one of comfort. I have 2 chairs in my office, both will displace my weight evenly, yet only one is comfortable.
     
  9. Apr 4, 2005 #8

    DaveC426913

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    How do the two displace your weight evenly? They must do so by different means. Can you elaborate?

    I suspect one is molded but hard, while the other is cushioned. The cushioned seat will dynamically mold to distribute the weight evenly, no matter how you reposition yourself. A hard seat is only a factory-designed guess at what your butt is shaped like*.

    However, if an exact mold of your butt was taken, it would be every bit as comfortable as the softest air-cushioned pillow - as long as you were motionless.

    The pillowed seat isn't intrinsically more comfortable, it's just more adaptable at suiting your position.



    *As this is a scientific discussion - we should deal with facts. In the interest of science, please send pictures of your butt. :rofl:
     
  10. Apr 4, 2005 #9
    lmao... :rofl:

    One is 1960's high tech{ultra modern} faux pleather with cotton batting filler. Looks really cool, but uncomfortable.
    The other one is 1990's closed cell foam under a layer of open cell foam with tweed like material incaseing it all. We are talking butt heaven here.
     
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