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Projectile motion with drag

  1. May 29, 2009 #1
    hey all

    I have a question and I want to quickly get an answer

    how to calculate projectile motion with drag a formula even if it is hard would be good

    mvh. patrick

    sorry my spelling I'm from abroad
     
  2. jcsd
  3. May 29, 2009 #2

    mgb_phys

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    The drag depends on the speed and shape ( for simple shapes you can look this up )
    The only difficulty is that the drag changes with speed, and of course the drag causes the speed to change - so you will need some calculus or a computer

    see http://en.wikipedia.org/wiki/Drag_(physics)#Drag_at_high_velocity for a good explanation
     
  4. May 29, 2009 #3
    I can not find the formula
     
  5. May 29, 2009 #4

    mgb_phys

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    The formula for the force is
    F_drag = 1/2 ρ v^2 Cd A

    ρ is the mass density of the fluid,
    v is the velocity of the object relative to the fluid,
    A is the reference area, and
    Cd is the drag coefficient

    The force acts against the motion, you can use this along with the normal projectile equations.
     
    Last edited: May 29, 2009
  6. May 29, 2009 #5
    how ?

    please write the whole formula
     
  7. May 29, 2009 #6

    berkeman

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    He did give you the formula. Did you read the link he provided above? What is the context of your question -- what are you trying to do? Is this for school work?
     
  8. May 29, 2009 #7
    hey sorry way I am a little stupid but what of it there are many and I would also like a description of the parameters and why I am generally very interested in physics, mathematics, astronomy and chemistry and I spend much of my spare time at why exactly this formula because I make an excel sheet with different formulas and I lacked only the
     
  9. May 29, 2009 #8

    berkeman

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    Here's a web page with more details about the formula. I found it by googling air resistance drag forumula.

    http://en.wikipedia.org/wiki/Atmospheric_drag

    .
     
  10. May 29, 2009 #9
    sorry but it is shown the same
     
  11. May 29, 2009 #10

    berkeman

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    Yes it is the same. That is the equation for drag. Why is it not what you are looking for? What are you actually trying to do or calculate?
     
  12. May 29, 2009 #11

    mgb_phys

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    i think the postor wants an equation for projectile motion including drag, I assumed it was hw and was trying to explain why the answer was more complicated.
    If they don't understand why they need a differential equation then posting one isn't going to help.
     
  13. May 29, 2009 #12
    I am looking for a formula which calculates the max throw distance
     
  14. May 29, 2009 #13

    berkeman

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    Show us how you calculate it assuming no wind resistance first. Then maybe we can offer a hint of how to go about factoring in wind resistance. What year are you in school?
     
  15. May 30, 2009 #14
    ok calculation of projectile motion without air resistance

    v ^ 2 / 9, 82 * sin (2 * angle)

    I am in the 8th Class
     
  16. May 31, 2009 #15
    hello again

    there is none who has written a response and I still need one but I have another question, the weight is not a significant drag on and show how yes
     
  17. Jun 1, 2009 #16

    berkeman

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    Does that equal the horizontal distance before landing?

    Have you looked at the Stoke's Drag equations and simulation at the wikipedia.org link that I posted earlier?
     
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