Question

So what I nedd is simple – how to create a drag and dropable circle with flex 4 and AS3 and using Box2d make it fly some more in the direction of drag and than stop?

Answer 1

Use LinearDamping.

This is how I used it in my top down shooter to slow the object down if linear velocity stopped being applied.

//Body is created using body definition
var b:b2Body = GameCore.environment.world.CreateBody(bodyDef);

//Fixture definition holds data such as density, friction and shape
var fixtureDef:b2FixtureDef;
fixtureDef = new b2FixtureDef();

//Define vertices etc in polygon shape
var shape:b2CircleShape;
shape = new b2CircleShape(Values.ptm(_diameter / 2));

//Assign values
fixtureDef.shape = shape;
fixtureDef.density = 1.5;
fixtureDef.friction = 0.3;
fixtureDef.restitution = 0.45;

//Add fixture to appropriate body
b.CreateFixture(fixtureDef);    

//Movement Physics Settings
b.SetLinearDamping(_linearDamping);
b.SetAngularDamping(_angularDamping);