# Paper plane physics question

Wolv3r
Hello Guys.

Maybe you got in the past some similiar questions :)

I'm a game developer and I'm programming a game with a paper plane and I want to achieve a nearly real physic.

What I got so far:

trust = the speed when I throw the paper plane.
drag = dragcoefficient * airdensity * trust² * surface / 2
lift = 0.5 * airdensity * velocity² * wingarea * lift coefficient
gravity = weight * 9.822 / (24 frames per seconds)
velocity = trust - drag - lift + gravity

So, my problem now is this:

• the correct lift coefficient:
How can I calculate the lift coefficient with aoa? Here on this forum I found the following formula:
Cl = Cl(2d slope) * (AR/AR+2)*aoa

But what is 2d slope, and how can I calculate the Cl when I don't have the Cl? And what is AR?
• When I throw the paper plane, and it's moving upwards, the speed is increasing. But it must be decreasing:
I know, that I calculate the lift into velocity. So it must be increasing. But how is it in reality?

Greetings and thanks

Wolv3r