A zipper is a kind of wedge – or a lot of little wedges!
For a project about wedges, collect as many different kinds of wedges as you can find around your house and on your block. What are the wedges made of? Try to find some thin, long wedges (like knives or nails) and some thick, short wedges (like a splitting maul). Are all wedges for cutting things apart? How about zippers? Is a zipper a kind of wedge? Why? What about corkscrews? Doorstops? Pencil sharpeners? How does friction affect the work of a wedge?
Try using a wedge to split a wooden log with a sledgehammer. What kinds of wedge work best? Why?
More about wedges
More about simple machines
Bibliography and further reading about wedges and other simple machines:
