“Troll physics”: Buoyancy for infinite power [duplicate]

Possible Duplicate:
What is the fallacy in this infinite motion machine?

Most of the "troll physics" images I can figure out, but this one has me stumped. What is broken about the following machine's physics?

-

migrated from skeptics.stackexchange.comApr 17 '11 at 13:59

This question came from our site for scientific skepticism.

marked as duplicate by Ted Bunn, mbqApr 17 '11 at 15:22

You mean apart from the spelling? – DJClayworth May 31 '11 at 18:59
Yes, I did mean apart from the spelling. – Ricket Jun 1 '11 at 3:15
It actually stalls! The force of water pushing down on the entering ball is greater than the bouyancy of the balls above. The only thing keeping the water from running out is the seal closing. – Mike Dunlavey Nov 17 '11 at 14:08

The problem is in the seal.

The amount of work to move the seal against the water pressure is the same amount of energy that is gained by the balls when they are pushed up by the water.

Even if we remove the seal and we imagine a magic "one-way pass-through" wall, the ball would still need to displace the same volume of water as itself in order to get into the tank.

-
Actually they can't even start to get into the tank. The force needed to overcome the water pressure is greater than the bouyancy of the balls above. It wouldn't be equal unless the balls above were coelesced into a single cylinder from botton to top having the diameter of one ball. – Mike Dunlavey Nov 17 '11 at 14:19