Wind force, drag, something :v

520

Heyy uh I have this problem I'm confused about; there is a body at rest (a sheet of cardboard set at an angle to electronic scales) and a fan blowing at the surface area. There is noticeable difference when I adjust the speed of the fan, the angle it sits at and the distance to the fan. Anyway I need help with the wind force equations, if I have the right equations.

These are the ones I have:
(Wind force) F= A* P* Cd [A: area of item, P: wind pressure, Cd: drag coefficient <- Huh??]
and
(Wind pressure) (1/2)*(density of air)*(wind speed)^2*(Shape factor)

Can somebody explain what the constants are and how to work them out, I would prefer if the responses are explanations not just links that are going to confuse me further

Any help will do :)

CWatters

not my field but the equation I remember is the one here..

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

You can look up Cd for some standard shapes..

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

The best method of working out Cd for your set up is to run the equation backwards. eg measure the drag force at various known wind speeds and plot a graph.