Seriously guys. I use normal vector math on it and it works fine.
You can take into account the forces.
Acceleration of paddle and ball and gravity and so forth.
Don't add gravity unless you want a very different game. In fact, for Arkanoid/Breakout, you don't want to change the ball speed at all. "Simple" physics of reflecting the ball is sufficient for Arkanoid. Pong needed a more complicated physics arrangement (which wasn't very realistic, BTW) because it needed a way to actually control the ball. Once a developer has basic physics down in his game, it's quite easy to add the ability to deflect the ball by moving the paddle while it hits.