Regarding the previous post, here's some videos you may want to watch (PS: obviously, i don't need to tell you where the source is from. if you really don't know then it's from youtube. :)

This is a rather interesting explnantion about center of gravity as its half-science lesson, half drawing lessons. haha.




This video is about an experiment, in the first few seconds,everything is normal then it became... well.... not normal . o-o