Students continue their pyramid building journey, acting as engineers to determine the appropriate wedge tool to best extract rock from a quarry and cut into pyramid blocks. Using sample materials (wax, soap, clay, foam) representing rock types that might be found in a quarry, they test a variety of wedges made from different materials and with different degrees of sharpness to determine which is most effective at cutting each type of material.
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- International Technology and Engineering Educators Association: Technology
- D. Tools, materials, and skills are used to make things and carry out tasks. (Grades 3 - 5)  ...show
- Next Generation Science Standards: Science
- Define a simple design problem reflecting a need or a want that includes specified criteria for success and constraints on materials, time, or cost. (Grades 3 - 5)  ...show
- Determine how different materials break using differently-angled wedges.
- Describe why simple machines are used and how a wedge exerts a force.
- Demonstrate why material selection and material science is important to engineers.
- Understand that because simple machines do their jobs so well they are still used today.
- 1 soap or wax block (~5 cm x 5 cm)
- 1 clay block (~5 cm x 5 cm)
- 1 foam block (~5 cm x 5 cm)
- 1 Styrofoam block (~5 cm x 5 cm)
- Wooden wedge (approximately the size of a typical doorstop [5 cm x 10 cm x 5 cm])
- Balsa wood wedge (~3 cm x 3 cm x 6 cm)
- Plastic wedge (~3 cm x 3 cm x 6 cm)
- Styrofoam/foam wedge (~3 cm x 3 cm x 6 cm)
- A variety of demonstration wedges with different angles and materials. For example, a plastic knife, putty knife, table knife, metal screwdriver or chisel (and a small hammer to use with the chisel).
- Some demonstration quarry material. For example, a half stick of cold margarine, a brick, etc.
|Angle:||The "sharpness" of a wedge.|
|Design:||(verb) To plan out in systematic, often graphic form. To create for a particular purpose or effect. Design a building. (noun) A well thought-out plan.|
|Mechanical advantage:||An advantage gained by using simple machines to accomplish work with less effort. Making the task easier (which means it requires less force), but may require more time or room to work (more distance, rope, etc.). For example, applying a smaller force over a longer distance to achieve the same effect as applying a large force over a small distance. The ratio of the output force exerted by a machine to the input force applied to it.|
|Quarry:||A pit from which rock or stone is removed from the ground.|
|Simple machine:||A machine with few or no moving parts that is used to make work easier (provides a mechanical advantage). For example, a wedge, wheel and axle, lever, inclined plane, screw, or pulley.|
|Tool:||A device used to do work.|
|Wedge:||A simple machine that forces materials apart. Used for splitting, tightening, securing or levering. It is thick at one end and tapered to a thin edge at the other.|
|Work:||Force on an object multiplied by the distance it moves. W = F x d (force multiplied by distance).|
Before the Activity
- Gather teacher demonstration materials.
- Prepare student group activity materials.
- Before making copies of the The Wedge Worksheet, fill in the table column descriptions with the wedge materials the students will be using, for example "wood," "plastic" and "Styrofoam" (or have the students do this). Fill in the row descriptions with the type of rock material the students will be using, for example, "foam," "wax" and "clay" (or have the students do this).
With the Students
- Teacher Demo: To give the students a visual understanding of a wedge and how it can be used as a tool, lead a demonstration using wedges as cutting tools. For the demo, the material being cut should be at a larger scale than what the students will do in their group activity. Use a variety of wedges, such as a chisel and hammer, and a plastic knife, on two very different materials, such as a brick and a stick of cold margarine. Some of the wedges will not be successful at cutting the hard materials, due to the wedge angle being too dull or the wedge material being too weak. Having two very different "rock" samples (brick and margarine) helps students understand why we need to design different types of wedges that are made from different materials, and introduces the idea of the importance of appropriate material selection.
- For the student group activity, divide the class into pairs of two students each (although groups of three work well, too).
- Direct each team of students to test their given wedges on each of their given "rock" sample materials. Allow them ~20 minutes to complete the activity.
- Instruct the students to record the performance of each wedge and "rock" sample on their worksheet, using the provided rating scale.
- As a class, conclude the activity by comparing test results among all teams and holding a class discussion. Which wedge/rock combinations were successful? Which were not? Why? How are the wedge angles and points different from each other? Which wedge had the sharpest angle? Which had the biggest cutting surface? How does this make a difference? (Possible answers: A larger cutting surface allows the user to exert more force on the object being cut.) Why do you think engineers design different types of wedges? (Possible answers: Depending upon the characteristics of the material to be cut, they might need to design stronger, but more expensive wedges to cut hard materials.) Why is material selection an important engineering job? (Possible answer: If you choose the incorrect material for your wedge, the tool will not work well and your project may not be successful.)
- While safety protection is not required, students should be aware that wedges have sharp edges so safety precautions need to be taken when handling them.
- Students should not be given metal wedges such a nails.
Activity Embedded Assessment
- For lower grades, a pencil can be used as a wedge to simplify the amount of materials. In this version, students learn how just one material cuts through various types of other materials, such as marshmallows, wax, sandwiches, etc. Have them rate the success of the pencil in cutting each material so they come to understand how a wedge can be used to split materials.
- For higher grades, assign students the task of extracting 4 cubic cm of each material using the provided wedges.
Bochnacki, Andrzeh. 2005. O Piramidach Inaczeh. Andrzej Bochnacki (Polish engineer). Accessed January 18, 2006. (An excellent animation shows how heavy stone blocks might have been systematically moved up an incline plane using many human-powered wedges. Click on Site Map, then click on Transport on the Ramp.) http://www.swbochnacki.com/
Construction of the Great Pyramid, Construction Theories. World-Mysteries.com. Accessed January 18, 2006. http://www.world-mysteries.com/mpl_2_1.htm#Machines
Nature & Science: Geologic Resources, Abandoned Mineral Land: Nature & Science. Updated October 19, 2003. National Park Service, U.S. Department of the Interior. January 18, 2006. http://www2.nature.nps.gov/geology/aml/
Lindsey Wright, Lawrence E. Carlson, Jacquelyn Sullivan, Malinda Schaefer Zarske, Denise Carlson, with design input from the students in the spring 2005 K-12 Engineering Outreach Corps course.
© 2005 by Regents of the University of Colorado.
Integrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder
Last modified: September 1, 2015