Click and drag a bit.  Then watch.

Other version 1
Other version 2

friction = .8;
yOffset = 200; //for display purposes only
numNodes = 100; //count of points
Width = 550; //width of display
drag = false;
points = [];
for(i = 0; i < numNodes+2; ++i){
	o = new Object();
	o.y = 0;
	o.yV = 0;
	points.push(o);
}

this.onEnterFrame = function(){
	clear();
	lineStyle(0,0);
	beginFill(0);
	moveTo(-1,yOffset);
	for(i = 1; i <= numNodes; ++i){
		avg = (points[i-1].y+points[i+1].y)/2;
		points[i].yV += (avg-points[i].y)/2;
		points[i].yV *= friction;
		points[i].y += points[i].yV;
		lineTo((i-1)*Width/numNodes,points[i].y+yOffset);
	}
	lineTo(Width,yOffset);
	lineTo(551,401);
	lineTo(-1,401);
	lineTo(-1,yOffset);
	if(drag){
		el = Math.floor(_xmouse*numNodes/Width+1);
		if(el < 1)
			el = 1;
		else if(el > numNodes)
			el = numNodes;
		points[el].y = _ymouse-yOffset;
		points[el].yV = 0;
	}
}

this.onMouseDown = function(){
	drag = true;
}
this.onMouseUp = function(){
	drag = false;
}