Simple Machines.....Another Kind??!!

[SuperNerd]

Hey, I am pretty new to the forums but I think I have a pretty valid question.

I have a physics teacher and in class we are talking about simple machines. He believes that there is another simple machine besides just the main two: Lever, and Inclined Plane. There are others like pulley, wheel and axle, etc. But he thinks that there is another one that is listed with the main six. I have done some looking and the only other thing I have some up with is possibly a gear, but I think that can be classified as a wheel or better yet a lever. I would like some of your guys thoughts, I have until Friday to figure it out and help would be greatly appreciated!!!!!!

[iglak]

there's supposed to be six: lever, inclined plane, pully, wheel and axel, wedge, and screw.

pully, wheel and axil, and lever can all be classified as types of levers
wedge, screw, and inclined plane can all be classified as types of inclined planes.

[SuperNerd]

yes I realize that, but my professor says that there is one other type of machine that is sposed to work