You can get all of such opensource APIs at one one place: http://actionscriptapis.com/

Nice to see all the API's at one place. Check them out...

So, i had to modify the APE source to rename the Vector class in APE and change the reference of Vector in APE source with the new name. Then i could able to run content with APE on Flash Player 10. You can download the modified source from here.

Making Particle Dragable:

After successful in running the content on Flash Player 10, i wanted to check out how drag works on APE particles. There are separate class files called 'DragableCircleParticle.as' and 'DragableRectangleParticle.as' under Files section of APE Google Group.

Place these .as files under 'source\org\cove\ape' Folder of APE.

Using these classes can make our work easy in making particles dragable.

These dragable particles can be initialized as follows:

DragableCircleParticel(x:Number, y:Number, radius:Number, fixed:Boolean, mass:Number,elasticity:Number, frictio:Number);

DragableRectanlgeParticle(x:Number, y:Number, width:Number, height:Number, rotation:Number, fixed:Boolean, mass:Number, elasticity:Number, friction:Number)

Here is the sample code to make use of these classes:

stage.frameRate=60;
import org.cove.ape.*;
import flash.events.Event;
import flash.events.MouseEvent;
import flash.events.Event;

addEventListener(Event.ENTER_FRAME, run);

var apeholder:MovieClip = new MovieClip();
apeholder.graphics.drawRect(0, 0, 550, 400);
addChild(apeholder);

APEngine.init(1/3);
APEngine.container=apeholder;

APEngine.addForce(new VectorForce(false,0,2));
var examplelevel:Group = new Group();
examplelevel.collideInternal=true;

var leftwall:RectangleParticle=new RectangleParticle(5,200,10,600,0,true);
leftwall.setStyle(3, 0x000000, 1, 0xFFFFFF,1);
examplelevel.addParticle(leftwall);

var rightwall:RectangleParticle=new RectangleParticle(545,200,10,600,0,true);
rightwall.setStyle(3, 0x000000, 1, 0xFFFFFF,1);
examplelevel.addParticle(rightwall);

var bottomwall:RectangleParticle=new RectangleParticle(275,395,550,10,0,true);
bottomwall.setStyle(3, 0x000000, 1, 0xFFFFFF,1);
examplelevel.addParticle(bottomwall);

var block:DragableRectangleParticle=new DragableRectangleParticle(Math.random()*550,- Math.random()*50, 80, 80,0, false,3);
examplelevel.addParticle(block);

var wheel:DragableCircleParticle=new DragableCircleParticle(Math.random()*550,- Math.random()*50, 20, false,3);
examplelevel.addParticle(wheel);

APEngine.addGroup(examplelevel);

function run(event:Event):void {
	APEngine.step();
	APEngine.paint();
}

Here is the output SWF.

Hope this would be helpful...

I just tried APE and made this simple SWF as a beginning into the world of Physics in Flash. You can drag these RectangleParticles which you see in this swf. You can get the SWF here.

One issue which i faced while doing is that there is some compatibility issue with APE and Flash Player 10. As the Vector Class used in APE will conflict with new Vector of Flash Player 10.

I had to fix with by changing the class name and all the references to Vector class in APE. With this i could able to succeed in running APE on Flash Player 10.

You can download the working modified APE Source for Flash Player 10.

I am still trying to figure out how to rotate the RectangleParticles on bounce. In this example, RectangleParticles are not bouncing. Will try to figure it out and will post soon about it...

ActionScript Physics Engine (APE)

APE (Actionscript Physics Engine) is a free AS3 open source 2D physics engine for use in Flash and Flex, released under the MIT License. APE is written and maintained by Alec Cove. The latest version available 0.45 alpha. You can get more info on APE at http://www.cove.org/ape/.

Fisix Engine

The fisix engine is a verlet based physics engine for flash written in Actionscript 3.0. This engine is aimed towards use in games and other relatively cpu intensive real-time applications.  The current version available is 0.5 Alpha.

This engine has got good documentatio in Wiki. You can find tutorials at http://wiki.fisixengine.com/index.php?title=FisixTutorials.

FOAM

FOAM is primarily intended as a resource for developers interested in simulating physics. It has a carefully thought out OOP structure and modular design.

Currently available version is 0.1 Alpha.

BOX2DFlASHAS3

Box2DFlashAS3 is an open source port of Erin Catto's powerful c++ physics library Box2D. Its the most updated engine with current version being 2.0.1.

Full sourcecode for the engine and examples can be downloaded from http://sourceforge.net/projects/box2dflash/.

Glaze : http://code.google.com/p/glaze/

A game and physics engine for Flash including:

• Rigid Body Dynamics
• Scene management
• Line of sight
• User Input
• Scrolling
• AI

You can view online demo at http://home.planet.nl/~borst595/glaze.html

PopShapes

This physics engine works with penetration detection of any object. Source for this engine is available at http://lab.andre-michelle.com/physics-engine.

These are a few which i could list from many Physics Engines available now. Try these and implement Physics in your Flash applications.