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  1. #1
    la vache fantôme phantomcow2's Avatar
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    Include air resistance in your calculations?

    In my physics class, all of our problems dealing with any type of motion say "neglecting air resistance" as a footnote.
    I was just wondering, what does a sample calculation look like when you don't neglect air resistance for a flying object? I don't know if he tells us to do this because it is either something we have not studied yet but will, or something he was not planning to cover because it is fairly advanced. I am just curious about what a sample calculation would look like
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  2. #2
    The Site Administrator: Currently at home recovering from a couple of strokes,please contact my assistnt admins for forum issues Tom Stormcrowe's Avatar
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    Quote Originally Posted by phantomcow2
    In my physics class, all of our problems dealing with any type of motion say "neglecting air resistance" as a footnote.
    I was just wondering, what does a sample calculation look like when you don't neglect air resistance for a flying object? I don't know if he tells us to do this because it is either something we have not studied yet but will, or something he was not planning to cover because it is fairly advanced. I am just curious about what a sample calculation would look like
    Here's a bike speed and power calculator site that also has an excellent tutorial on the math included. It takes into account air resistance AND density as well as wind speed and direction, ie: head or tail.
    http://www.kreuzotter.de/english/espeed.htm
    on light duty due to illness; please contact my assistants for forum issues. They are Siu Blue Wind, or CbadRider or the other 3 star folk. I am currently at home recovering from a couple of strokes. I am making good progress, happily.


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  3. #3
    2-Cyl, 1/2 HP @ 90 RPM slvoid's Avatar
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    Just add 1/2cpav^2.

  4. #4
    Senior Member DannoXYZ's Avatar
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    Quote Originally Posted by slvoid
    Just add 1/2cpav^2.
    That's like someone buying a Haynes manual to work on their car. Then flipping to the section on changing the timing-belt and the first step says, "Remove Engine"...

  5. #5
    無くなった HereNT's Avatar
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    Quote Originally Posted by DannoXYZ
    That's like someone buying a Haynes manual to work on their car. Then flipping to the section on changing the timing-belt and the first step says, "Remove Engine"...
    If it were a wiki and that first step was a link to steps for removing engines on different models of cars...

  6. #6
    Senior Member
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    Including a term in air resistance complicates the mathematics significantly.

    Taking freefall under gravity as an example, without air resistance the acceleration is constant, and can be integrated once or twice (as required) to give speed or position with respect to time.

    Including air resistance, the acceleration now has an extra term, not simply in v, but in v^2. So you've now a second order non-linear differential equation that in many situations will not be possible to solve explicitly.

  7. #7
    2-Cyl, 1/2 HP @ 90 RPM slvoid's Avatar
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    Quote Originally Posted by DannoXYZ
    That's like someone buying a Haynes manual to work on their car. Then flipping to the section on changing the timing-belt and the first step says, "Remove Engine"...
    Do you want to give this kid ALL the answers?

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