What do elementary students need to know about machines?

     Simple machines are so important that they are often included in third grade science curricula. But do they need to know Newton’s laws of motion, classes of levers and pulleys, and gear ratios? Developmentally, mid-elementary students do not have the math skills to do much work with these concepts, and they are just beginning to be aware of the physical world. Certainly some ‘pre-teaching’  would be helpful to prepare students for the detailed study of force and motion in middle or high school, but what is important?

     Using the 2006 NH Frameworks as a guide, PS 2 (3-4) / 1,3; PS 3(3-4) /1.1, 1.4, 2.1; and PS 4 (3-4) / 1.1,2,3 and 4.4 are the relevant sections. We can narrow the general areas of focus to the following:
    

measurement, observation of gravitation acting on motion, energy     
    transformations, and use/design of simple technology (tools)

Here is my translation of Frameworks lingo into useful teaching points:

* Machines help people do work by shortening the time or decreasing the effort    
   necessary to do a task.

* Machines are often used to transform one kind of energy into another more    
   useful form.

* Inventing and designing machines is a process which begins with a problem
   where the solution relies on creativity and experimentation.

* Designing machines and comparing designs involves measurement tools to find
   the best machine for the task.

* Inventions using simple machines have changed the course of human history.

I personally believe that the problem/design/invent/test/redesign/retest  paradigm achieves many of the goals of teaching science and technology. By introducing problem solving at an early age, the practical elements of scientific method, cooperation, and creative design can be integrated with other curricular areas. Thinking skills are emphasized over regurgitation of factual material, and content is introduced as a tool to solving a problem rather than a goal itself.