Physics with My 5 Yr. Old

I found a fun way to do a little physics with my 5 yr. old ... in the kitchen sink. I filled up the sink with water and then grabbed different objects around the house and with each item asked my son if he thought it would float or sink. It was surprising even to me that some of the objects I thought would float actually sank and vice versa. This idea came in a great little book that I found on Half.com for 1 penny (plus shipping) called '365 Days of Creative Play' by Sheila Ellison & Judith Gray.