Could you balance a book on just a single flat piece of paper?
No
Strengthening materials
- Which shape of pillar is the strongest?
- Which ways are used to strengthen materials used in buildings?
- What is the purpose of folding, tubing etc. in the building structures?
- How can triangles strengthen structures?
- Where in everyday life do we find examples of folding, tubing and braces?
- What is a strut and where is it used?
Ways to strengthen materials
There are different ways to strengthen materials to make a stronger structure. We can do this by changing the shape of the material. You may think that the shape may not make that much of a difference, but let's have a look.
Which shape is stronger?
Explore different ways to strengthen paper
MATERIALS:
- Up to 5 sheets of A4 paper for each group
- Pieces of sticky tape
- A number of identical or similar size books for each group
INSTRUCTIONS:
- In groups of 4, investigate different ways of using your paper sheets to balance a book.
- Look at the pictures below for some ideas.
- Use a piece of sticky tape if you need it.
- How many different ways can you find of balancing a book more than 10 cm above the desk or floor, using only 1 sheet of A4 paper? You can try this on your own or in a small group.
- Once you think that you have found all the ways you can do it, choose a member of your group to report back to the rest of the class on the ways that you have found.
- With your teacher's help, show each different method side-by-side on a table or on the floor at the front of the class.
Teacher note: This can be done numerous ways, by rolling the paper into a tube and balancing the book on top of the tube, or by folding the sheet of paper into various shapes with different cross-sections. Allow the children to explore and grapple with it, and when they report back, display an example of each different method at the front of the class.
QUESTIONS:
Which shape is the strongest? Why do you think so?
The investigation should show that the strongest shape that the paper can be folded or rolled into to support a weight would be a round tube.
What did we learn from doing this activity? Materials can be made stronger by changing their shape. An example is rolling the paper into pillars. Pillars can be circular, triangular or square. Which one do you think is the strongest?
Tom has a pile of books next to his bed at home. He wants to make a stand for these books so that his room looks a bit neater. He thought about making a stand using materials he can easily get hold of, such as paper. His idea is to make 4 pillars and then place a cardboard sheet on top on which to place his books. But, Tom does not know which type of pillar would be the strongest - triangular, circular, or square.
Let's help Tom and do an investigation to find out which shape of pillar is the strongest for him to make a book stand.
Teacher note: For this investigation the class can divided into three groups. Each group folds the paper to form a different shaped pillar.
Group 1: Circular pillars
Group 2: Triangular pillars
Group 3: Square pillars.
Each group will investigate only the strength of their pillar.
The conclusion will be made when the results of all groups are put together.
To make the investigation a fair test, each group must use the same :
- size and type of paper
- identical books
- platform
- amount of sticky tape
Explain this to the learners while doing the experiment - it would not be a fair test if each group used different paper and different weights of books. In the experimental design stage, encourage learners to ask questions such as "How will we know it is strong?", "What should we do to check it is strong?", etc. This will help learners to see that by placing books on top with increasing weight, you can test how strong the pillars are. Do not give them these answers outright, rather ask them the questions first and encourage them to think.
Which pillar is the strongest?
AIM:
Write down what you think the aim is for the experiment.
To investigate which type of pillar is the strongest: a triangular, circular, or square.
APPARATUS
- four sheets of A4 paper
- scissors
- sticky tape
- a piece of cardboard to form a platform as the lid of a box
- a number of the same type and size of books
METHOD:
- Each group will make and test a different pillar, either circular, triangular or square. Look at the image below to see how to make the different shaped pillars.
- In your group, make 4 of the same pillars out of the 4 sheets of paper (one sheet per pillar).
- You can use sticky tape if needed. Check the amount with other groups so that you all use the same amount, otherwise it would not be a fair test.
- Put a platform of cardboard on the folded pillars as in the picture below.
- Now go round to each group as a class and test the structures.
- Add books (one-by-one) onto the platform. Use the same books for each group and place the books on in the same order each time.
- Record the number of books that each structure can hold before collapsing on the table below.
RESULTS:
|
Groups |
Number of books |
|
Circular pillars |
|
|
Triangular pillars |
|
|
Square pillars |
Now draw a bar graph of your results. A bar graph is used to represent your results in a different way. Your teacher will guide you through the process.
On x-axis: three types of support. Circular, triangular and square
On y-axis: number of books
Heading: The graph shows the number of books supported by pillars of different shapes
CONCLUSION:
What is your conclusion from this experiment? Which shape of pillar is the strongest?
QUESTIONS:
Which shape pillar would you tell Tom to use for his book stand?
Dependent on experiment. It should however be the round pillar.
How did all the groups make sure that the experiment is a fair test? In other words what did you, the learners in your class, make sure was the same in all the groups?
The type of paper used, the number of columns (4), the type and size of cardboard for the platform, the number and size of the books, the amount of sticky tape used were all the same for each group.
Tubing and Folding
Materials are strengthened by shaping them into a tube (tubing).
Tubing is often used to make frames and for supporting weight. The tube can be in a number of shapes, as we saw in the investigation. It can be circular, square, triangular or even in a U-shape.
When exploring different ways to strengthen paper you discovered folding the paper also helped to strengthen it. Corrugated cardboard and bubble wrap plastic are examples of strengthened folded materials .
Corrugated iron is another example of how folding makes a material stronger. Look at the picture below of a sheet of corrugated iron and a flat sheet. Corrugated iron is much stronger which is why it is used for the roofs of some houses.
What is my school made of?
The Thunderbolt Kids need to investigate the uses of different materials in different schools. They have asked your help with your school.
INSTRUCTIONS:
- In groups of 4 you need to investigate the different materials used in the buildings and structures in and around your school.
- Look particularly for materials which have been tubed or folded, and for the use of struts and braces.
- Record your observations in the table below.
- An example has been provided:
|
Structure |
Material |
Ways to strengthen (Folding, Tubing, Triangulation) |
|
Roof |
Corrugated iron |
Folding |
- The strength of structures can be increased by changing their shape, using methods such as tubing and folding.
- Shapes of structures can be circular, triangular or square.
- Braces across corner joints in structures increase their rigidity and strength.
- Struts are used to strengthen or support structures.
Name some ways to strengthen paper to make a stronger structure.
Folding, making into a tube, placing more pieces together.
Choose which piece of metal below would be better to use for a roof, and explain why.
A. Corrugated metal sheet - it is stronger and will not bend as easily
Which piece of steel shown in the picture would you use as the stand for a basketball hoop? The flat piece of steel or the circular tube? Why?
The flat bar would bend too easily when weighted - rather use round tube which is stronger.
The upright poles of the carport shown in the picture are made of square tubing. Give two good reasons why they are not just made of solid steel the same size?
Solid steel would be very heavy, and very expensive.