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Wedges

Name of Corresponding Unit Plan: Edged Tools

Grade Level: 2-8

VT Grade Expectations
VT S:21 Students demonstrate their understanding of Force by investigating variables that change an object's speed, direction, or both, and identifying and describing the forces that cause the change in motion.

NY Standards
Key Idea 1: Clarify ideas through reasoning, research, and discussion

Content Areas: Science

Recommended Length/Duration: 30-50 minutes

Learning Goals:

Students will examine the ways a wedge distributes a force over a distance.  Intermediate students will measure the effort and resistance distances to determine the mechanical advantages of various wedges

Description/Sequence

  1. The teacher should review how Inclined Planes make work easier by distributing a force over a distance.  Demonstrate with a drawing or wedge model how a wedge is actually a portable inclined plane. 
  2. Describe how a wedge applies a force first to a very small area (the cutting edge) and then gradually widens the parting of the two surfaces it divides.  Demonstrating with a log splitter, splitting maul, or thick chef’s knife can be effective.
  3. Show how the effort distance is the length of the triangle formed by the wedge and the Resistance distance is the thickness of the triangle formed by the wedge.
  4. Have students observe a variety of edged tools.
  5. After examining different tools, discuss how each wedge is sized for the task it is intended for.  Guiding questions include:
    • Why are some wedges sharp and others more blunt?
    • How do you determine the size of a wedge tool?
    • How do less efficient wedges make up for low mechanical advantage in doing their intended job?

Assessments Informal assessment based on participation and general understanding of main ideas.

Materials/Resources A demonstration tool and object to split or cut.  A collection of edged tools of different sizes and purposes (e.g. different size knives, axe, maul, splitting wedge, plane, cheese slicer, potato peeler, nail)

Special Considerations Care must be given to the use of edged tools.  There should be no very sharp edges and students need to be properly supervised to avoid their careless use.