Lotto numbers and the heavier ball

[gnikolaidis]

I am referring to a method used by some lotto operators to determine the winning numbers. In the particular method a number of balls having the same size and (supposedly) weight are put inside a canister where the are put into random motion by means of pressurised air. At some point, the influx of pressurised air stops and slowly the balls come to rest - at which point a ball finds its way out from a hole at the bottom of the canister. Thus, and by referring to the number painted on the ball, the winning numbers are determined in succession.

However, I remember from my high school elementary physics course a similar experiment - which our physics professor code named "Maxwell's Devil" - where a number of balls where put into random motion inside a spinning sphere and at the end the same one ball always came out of the hole in the canister. It turned out that this particular ball was slightly heavier than the rest, thus forcing it self as the first ball always to come out.

I am trying to locate on the web a practical and theoretical explation of the physics involved, but unfortunately I cannot find anything related to this matter. Can anyone help with any references?

Thanks.

 

[Pengwuino]

Geez, that doesn't sound right...

 

[KingNothing]

Well without knowing what you mean by "random motion inside a spinning canister", I doubt anyone here can explain it. Obviously the motion was not completely random, if results are preceded by the weights of the balls.

 

[Pengwuino]

I'm imagining like... how they do the lotto on TV or some bingo halls with the balls flying around because there's a stream of compressed air being fired from the bottom up into the big sphere and one being pulled from the bottom after the air stops and all the balls fall down.

It might make sense if the balls were mixed up after the air was off because that might give the ball time to fall to the bottom of the group of balls.

 

[gnikolaidis]

Well without knowing what you mean by "random motion inside a spinning canister", I doubt anyone here can explain it. Obviously the motion was not completely random, if results are preceded by the weights of the balls.

Imagine the canister is a round sphere which is put into rotational motion with a number of balls inside it. As the sphere rotates with high speed the interaction of the balls with the walls of the canister and with each other makes them appear to move in a random motion, like the molecules of a hot gas. When the sphere comes to rest, the slightly heavier ball always comes out of the hole.

You are right that "random" is not appropriate, since the balls inside the sphere are not all of equal weight, one is slightly heavier. But to the observer, who does not know this fact, appears to be random.

The experiment works and I suppose anyone with the right equipment can replicate it. I need however an explanation of the phenomenon with the involved physics.