applying acceleration movieclip

[grebs]

I am trying to add acceleration to a movieclip called Ground. I have written this code

package {
import flash.display.Stage;
import flash.display.Sprite;
import flash.ui.*;
import flash.events.*;

public class Ground extends Sprite{
private var xVel:Number = 0;
private var xAcc:Number = -0.25;

public function Accelerate()
{
init();
}

private function init():void
{
stage.addEventListener(KeyboardEvent.KEY_DOWN, go);
}

private function go(event:KeyboardEvent):void
{
if(event.keyCode == Keyboard.UP){
xVel += xAcc;
}
}
}
}

The movieclip loads fine and i get no errors, but when the up button is pressed nothing happens. Can anyone help?

[Krilnon]

Why would anything (visible) happen? You never change the x property of your Ground object.