Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: The Physics of a Kite

  1. Apr 30, 2012 #1
    So, I am a student of 3rd quarter calculus based physics class, we have to do a project so I was thinking of picking the physics of a kite with a miniature visual of a kite in like a state of static flight if I can with a controlled fan and a small paper kite. I just want to verify that this project isnt more of a difficult topic that I think. So, for a kite to glide it has to have a drag force from the wind hitting the kite at an upward angle so the projected upward force is equal or greater than the downward force of gravity with the addition of the tension of the string holding it down if the drag is greater. But when applying these forces to an actual kite I would apply these forces at the kites center of mass, correct? With the drag force proportional to the area of the kites surface? Do I have to find the torque created throughout the rigid surface? and When does the bernoulli's principle come in play? Is there anything I am forgetting or is this about it?
  2. jcsd
  3. Apr 30, 2012 #2
    The forces of lift and drag will act through the centre of pressure, not the centre of mass. NASA has an excellent series of pages on kite aerodynamics. Here's the one about centre of pressure.
  4. Apr 30, 2012 #3


    User Avatar
    Science Advisor

    A typical kite is really more of an airfoil. The way the lift and drag are generated on an airfoil are slightly more complex. Take a look at article on Thin Airfoil Theory. See if you can sort most of it out.

    In short, the resultant vector of drag and lift aren't along the line at which the relative wind moves. Unless the airfoil is stalled, the lift is significantly higher. (Though, kites can fly stalled.) Furthermore, the point at which the force is applied is the center of pressure, which isn't necessarily aligned with center of mass. In fact, for a kite, the center of mass is typically significantly aft of center of pressure.

    This really sounds like a quite doable project, but you should read up a bit more on airfoils in general and kites specifically.
  5. Apr 30, 2012 #4
    Thanks that really helps
  6. Apr 30, 2012 #5


    User Avatar
    Gold Member

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook