This lesson provides another perspective on modeling. Students are encouraged to look at existing mechanisms, such as scissors, tongs and extension hooks, and identify their basic mechanical parts. They then capture the underlying forms by making models of these devices in pegboard or cardstock.

*Classroom set of Mech-a-Blocks: both cardstock and pegboard.**Manufactured mechanisms that children can model. These could include scissors, pliers, tweezers, garlic presses, nut crackers, salad tongs, jar openers, fireplace tongs, expandable door hooks, retractable mirrors, and adjustable-arm desk lamps.*

**Review of modeling:**

Review the concept of modeling from the previous lesson: a model keeps essential features of the original, but leaves out those that are unimportant and/or get in the way of understanding. For example, a model of a Mech-a-Blocks construction doesn’t need to include all the holes that are not used, but those that are used need to be in the right locations.- Today we are going to make a different kind of model. We’re going to start with something someone else made, and see if we can make something that works the same way.

Provide examples of commercially made mechanisms. Each one should consist of links and pivots that can easily be modeled in pegboard or cardstock..*Here are some good examples*

- Today we are going to make a different kind of model. We’re going to start with something someone else made, and see if we can make something that works the same way.
**Modeling mechanisms made by someone else:**

For this activity, students should work in pairs. Give each pair a choice between pegboard or cardstock, and provide these materials, as well as fasteners, pencils for tracing, and crayons or markers, Post-Its™, paper, tape and scissors for decorating.

As students are working, visit the groups and assist them in thinking about how to proceed. What features of the original are important and which are not important? How are they deciding what sizes and shapes to use for the pieces? What method are they using to record the hole locations?

This work may take more than one period. Provide time for them to continue until they are satisfied with their models.**Whole-class discussion:**

Provide time for each pair to share their model. Ask each pair to talk about these issues:*What was the object you were trying to model? What is it used for?**What did you do to make your model? How many pieces did you need? How many fasteners? How did you know?*- *How is your model different from the real thing? How is it similar? *
*What problems did you run into? What did you learn?*

**Science Notebook:***Draw a picture of your model and label it.**How did you make your model?**How is it different from the real thing? How is it similar?*

**Outcomes**:

Students should be able to construct a model of a manufactured mechanism, and be able to compare the operation of the model with that of the original.**Assessment:**

Show students a manufactured mechanism, accompanied by an accurate pegboard model.*How are these similar? How are they different?*

Show students a manufactured mechanism, accompanied by a model that has some incorrect hole locations.*How are these similar? How are they different?**If I wanted my model to work more like the original, what would I need to do?*