I was trying to make a cannon, too..... then I got froggy and built a tube filled with TNT out of obsidian, jumped in a minecart and had a buddy drop me inside. I didn't go anywhere when the TNT went off.
Anyway, TNT isn't physics enabled in this version so you can't make the really crazy cannons you see from the PC. I don't think the wet cannons work in this version, either, but I haven't tried it.
Anyway, TNT isn't physics enabled in this version so you can't make the really crazy cannons you see from the PC. I don't think the wet cannons work in this version, either, but I haven't tried it.