Children next examine the constructions they have made. They investigate some of the patterns that connect form and function. These patterns involve the different uses of fasteners, which determine whether or not the constructions have moving parts.If they do, they are mechanisms!
Children's Mech-a-Blocks constructions from previous days.
1.Focusing on structures vs. mechanisms. Begin by having children describe what they have made. Select some constructions that have moving parts and some that don’t. Demonstrate the difference, by holding the base of each one, and trying to make other parts move. The base is usually the largest piece. It’s the piece you hold steady while trying to make the other parts move over it. Anything with moving parts is called a mechanism, while anything that can move only as a whole is called a structure. Write these two words on chart paper.
Help students sort their constructions into the two main categories, mechanisms and structures.
Using words and pictures, show what happens when you try to move parts of what you made.
3.What do fasteners do? Focus students’ attention on how they used fasteners. Use examples of their work to show three basic ways:
A fastener that goes through one piece only: What (if anything) would be different about the way things would workif it weren’t there?
A fastener that goes through the base and another piece: What is the job of this fastener? Which pieces can move and which ones can’t?
A fastener that goes through two pieces but not the base: What is the job of this fastener? Which pieces can move and which ones can’t?
Help them see that the first type just moves with the part it is attached to – it does not change anything about the movement of the other parts. The second type is a fastener that cannot move itself, because it is attached to the base, but it may allow other parts to move, depending on whether there is a mechanism or a structure. The third type of fastener generally allows one part to move another part.
4.What makes something a mechanism or a structure? Using the discussion about fasteners, return students’ attention to the categories of mechanisms and structures. Demonstrate one of each, and have students identify the type b. fasteners in each one. Then ask them to look at their own constructions:
In a structure, what do you notice about the number of fasteners attaching a part to the base?
In a mechanism, what do you notice about the number of fasteners attaching a part to the base?
Students should discover that a mechanism uses at most one fixed fastener to attach a piece to the base, while a structure uses two or more fixed fasteners to attach a piece to the base.
Show students a simple mechanism made with Mech-a-Blocks:
How could I turn it into a structure?
Show students a simple structure made with Mech-a-Blocks: