What are simple and compound machines?

If you follow me on facebook you would have seen my link to an awesome website I love to use with my students called EdHeads. The site is http://www.edheads.org. I have used their simple machines interactive activities with students in years 3 and 4 a few times. Apart from the general layout, graphics and age appropriateness of the activities I really like that the students can't move on until they have completed the questions and demonstrated a level of comprehension.

So why the reference to Edheads?

I have been working hard on a unit on simple and compound machines for students in year 3 and 4. 
So what are simple and compound machines?
There are six common simple machines: lever, pulley, inclined plane, wheel and axle, screw and wedge. Essentially they all make life easier in one way or another. It could be that they make it easier to move a load, requiring less effort or force or that they connect or seperate two things.

A broom is a lever. The fulcrum or pivot point is the user's wrist. It moves a load (the dirt) with the load arm and is pushed with the force arm (where we hold it).

Compound machines are objects that have two or more simple machines included in them. A pair of scissors is a great compound machine. 

It has a lever (the handle) and a wedge (the blades of the scissors). A more complex compound machine is a stapler and staples.

A stapler has a lever - the handle, a wedge - the staples a wheel and axle - the pivot point for the lever and an inclined plane - the slant for papers to slide up under the staple dispenser. 

The unit I am creating has activities for students to develop a deeper understanding of simple and compound machines.
I really find that students love the rotational activity work that I have included and as you know I love my students to have hands on practical activities, while following scientific process and being encouraged to think for themselves.

This will be a very comprehensive unit with powerpoints, worksheets and the like so it can't be rushed. In the meantime have a look at Edheads. There are some other activities listed there also for older students such as the virtual knee replacement - looks like fun!