Structure Influences Strength and Stability
Lesson 8 of 16
Objective: SWBAT state that triangles, wide bases and strong materials make a tower more stable.
Watch the video for an activity description and to preview some of the resources in this lesson.
NGSS/Common Core Connections
The children will be learning in an authentic way, that different properties are suited for different purposes. This lesson also gets at the heart of the cross-cutting standard in which the children need to know that the shape and stability of structures in the designed objects are related to their function.
These resources need to be pulled up on your Smartboard:
I gather the students on the carpet so they are able to see the Smartboard. I begin the discussion by asking some questions about the Watts Towers and the man who built them, Simon Rodia.
Before we started this unit or read anything about Simon Rodia, I asked you an important question.
I pull the Essential Question up on the Smartboard. We read the question together.
We are going to look further into that question by taking a look at the books we have read about the Watts Towers. By looking closer at the books, let's see if we can find out any new information.
What did Rodia use to create his towers? (cement, steel, sand and lots of tiles/junk) Where did he get the materials? (He bought the foundational materials but he collected the broken tiles and junk from around the neighborhood). What did he make with the cement and sand? (concrete) Why do you think he used these materials?
I want to touch on some of the science standards. I want the children to start thinking about the basics of why people chose items for building according to the task at hand. They choose materials according to their properties. Towers need to be strong and stable. Engineers and builders choose building materials that are strong, such as cement, because it helps create a strong structure.
How did Simon Rodia use small items to make something else?
Again I want to touch on the idea that you can create something big from a small set of pieces. He used steel bars and cement to create the base structure, but then added all sorts of small pieces to make his creation even better. I also show them this List of materials that Simon Rodia used from the back of the book. It's so mind-boggling how many pieces he actually used in this structure!
We take a look at this page about testing from the book.
In the book it said that some city officials thought Rodia's towers might be unstable. So they tested his towers using a wind-load test. The towers passed the test and proved they were stable. Why do you think his towers were so stable?
I pull up an actual photo of the Watts Towers for a visual as the partners are discussing their ideas. I want them to notice what type of structures Simon Rodia used to make his towers stable. I also want the children to notice that the shape of the towers and the materials used influences the stability.
As the children discuss these ideas, I walk around the room and listen to them talk. I note their progress on a clipboard.
After the chidren have finished discussing their ideas about what makes Watts Towers so stable, we gather back again as a whole group to discuss.
The children comment that the towers are wide at the bottom and smaller at the top.
What did we already learn about that was wide at the bottom and smaller at the top?
The children were able to tell me towers and cones are made this way. I pull up a pyramid photo to remind them of other things with this shape. (Here is a Hancock Center photo that can be used if your children do not come up with that example).
What else makes the Watts Towers so stable?
The children tell me that the towers are made with many triangular shapes and are reinforced with concrete. This realization also gets them thinking about how different properties of materials make them suited for different purposes. Also that a set of objects can be built up from smaller pieces. This knowledge will help them when they are challenged to build their own towers later in this unit.
Since the lesson has included other elements, I chose to bring the discussion and focus back to building background knowledge for our engineering project. I pull up a photo of one of the pages from Dream Something Big about Rodia's insight on the use of triangles in building. After reading this page aloud to the children, we start a discussion.
Even though Simon Rodia did not go to school to be an engineer, he still knew about what it takes to make a structure, or in this case a tower, strong and sturdy. As a matter of fact, his work is now known worldwide as an engineering masterpiece. Knowing what you now know about building, what design principles do you think Rodia knew?
I want the children to relate the idea that Rodia used triangles since triangles add strength to structures. Triangles also help support the structure to make it more stable. Also, they should relate the idea that Rodia also made his structures with a wider base and a smaller top to make them more stable. Click here for a video clip of a student answer of what makes a structure strong.
I want to have the children tie all of the ideas together that we have learned so far. I pull the Structure Influences Strength and Stability Wrap-Up up on the Smartboard. We discuss the ideas together. Then I pass out the children's science notebook and turn to the page "What Makes a Structure Strong and Stable?
Now that we have reviewed what makes a structure strong and stable, I would like you to add to your chart. You will be adding to the second box. I would like you to write down what you now know that makes a structure strong and stable.