Hey guys. I have several questions (big test tomorrow!!) so here they are: Does anyone know what "Viscous fluid flow" and what "nonviscous flow" is? Could anyone explain to me generally what a barometer is? I don't get why a helium ballon floats but a regular air baloon sinks. I actually just don't get why a helium baloon floats at all. Ok, my next question may be a bit hard to understand- You have a piece of clay in a lump. You put it in water and it sinks. Then you take that same piece of clay and shape it like a boat and it floats. Why? Ok, that was the last one. Any help would on either one of these be greatly appreciated!