Constant force, with gravity, and correct collisions.

Hi,

I am looking for a way to have a constant force or velocity applied to a ball, as well as gravity that when it collides with a wall, it bounces off just as it would in real life.

I have tried a whole number of ways, such as setting the velocity to a speed every fixed update, this yields an unrealitic collision response when colliding with a wall.

I've also tried adding a force every fixed update, this still doesn't produce realistic collisions off the wall, on a slight angle the ball slides along the wall, rather than bouncing off.

How would I create a ball, that maintains a constant speed, that reacts to gravity, and bounces off walls realistically?

I'm stumped.

Thanks!