Lesson Summary
This learning experience will take two class periods. The students will learn that the dead load is the weight of a structure’s own material. They will learn that the live load is the added weight on a structure. They will learn that the live load and dead load of a structure affect its ability to stand. Students will think about the characteristics of a structure that can affect its ability to support loads.
Teacher Background
Using their own bodies as “structures,” students explore the effect that the weight of a structure’s own materials (dead load) has, and then test how added weight (live load) affects the stability of a structure. Live load is the added weight that is placed on a structure. Then the students test how dead load and live load affect the stability of their straw structures.
Set-up/Management Tips
- The book What It Feels Like to Be a Structure by Forrest Wilson is used in this lesson, and is included in the kit. The students, in groups of four, gather around a desk or small table. Two of the students stand on opposite sides of the desk and lift the desk off the ground. These two students and the desk now are considered the structure. These two students are now part of the building’s structure, and are therefore also part of the dead load. The other two students place books (live load), on different parts of the desk. Then the two students, placing the live load on the building, should ask the dead load students how the building felt when they had to lift the live load. The dead load students should report that they felt pressure or pulling stresses on different parts of their bodies as they lifted the desk with live loads on it.
- Make a class list on poster paper or the chalk board of the live load and dead load parts of a school building as outlined on page 68 of the teacher’s manual.
- The students can create a load tester out of string with a paper clip to hang washer weights (live load) on when testing their straw structures. The directions for making the load testers are on page 66 of the teacher’s manual. However many teachers have found that hanging the weights directly on paper clips is easier for the students to manage because tying loops at the end of the string can be tricky. It is important that the class weigh the load tester with a spring scale, either string/paper clip or just paper clip, and establish an agreed upon weight for the load tester. The load tester’s weight will be included in the weight of the live load.
- The large washers (live load), used in the kit can vary in size and weight among the kits. It is important to weigh them with a spring scale and establish an agreed upon weight for the large washers in your kit.
- The students need to establish agreed upon weights for the straws and paper clips for calculating their structures dead load. The students will need to count the number of straws and paper clips in their structures and calculate the dead load of their structures. It may not be possible to weigh one straw or paper clip with their spring scale. Have the students try to find the weight of straws and paper clips by weighing 10 or 100 and then finding the weight of one straw and one paper clip.
- Before calculating the dead and live load of the structures it might be helpful to review how to read a spring scale with the students.
- When the students start testing with their load testers on their structures, they should place the load testers on different parts of their structures. They should start with one washer and add more washers one at a time to the structure. The goal is to place washers as high as possible on the structure. The goal is to test which structure can hold the greatest number of washers (live load) at the highest possible point on their structure.
- Prior to having the students place the load tester and weights on the highest point of their structures, have the students make the data table, listed in the teacher’s manual on page 72, in their science notebooks. The manual suggests posting a large class poster of this chart in the classroom. The class poster should be titled Live Load/Dead Load and have columns labeled: Group/Dead load/ Live load/Height of Live load. Have the students duplicate this poster in their notebooks. The number of rows on the posters is determined by the number of groups in the class. When discussing this data, as a class, use the questions on teacher’s manual pages 72-73. Have the students think about the dead loads/live loads of the neighborhood structures and record their ideas in their science notebooks. Ask the questions listed on page 73 of the teacher’s manual.
- Discuss how they are using ratios to compare how the dead load relates to the live load. The concept of ratios will need to be reviewed with the students. Optional
- Review how shape, design, materials and size can all affect the structure’s ability to support loads. Invite the students to make additions or changes to the “Why Do Structures Stand?” or the “Principles of Good Construction” charts.
- The manual suggests having the students make a human pyramid in PE by using the directions on the website http://www.pbs.org/wgbh/buildingbig/educator/force.html.
- Optional book mentioned and not included in the kit Round Buildings, Square Buildings, and Buildings That Wiggle Like a Fish by Philip Issacson mentioned on teacher’s manual page 69. This activity focuses on how to read nonfiction books.
- Science notebook questions and writing suggestions for this learning experience are listed below:
- Have the students date and title a page in their science notebooks, “My Body as a Structure.” Teacher’s manual pages 67-68 instructs them to think about their bodies as structures, and write responses to questions listed on these pages.
- After discussing live load and dead load as outlined on teacher’s manual page 68 have the students to the questions listed on that page
- The teacher’s manual page 73 has directions for writing a summary.
Literacy Support
Scientific Vocabulary
The following words are key vocabulary words that will be introduced in this lesson and reinforced throughout the unit:
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