Unit 4: Stability

Stability: the state of being stable

Unit 4: Stability

¤  KWL CHART

Cross A Bridge by: Ryan Ann Hunter

illustrated by Edward Miller

What is a Stable Structure?

¤ Objects that are short and wide are stable. They have stability. This means they stand firm. Objects that are tall and narrow may be unstable. This means they are more likely to fall over.

¤ * Stand up activity.

Stability

¤ Structures are all around you. A structure is something that holds a load.

¤ Your school building is a structure.

¤  The car or bicycle that helped

you get to school is also a structure.

A spider’s web is one of nature’s structures.

Stability

¤ Structures need to be stable. This means they must be steady and not fall over. In this unit, you will learn about structures and what makes them stable

Why Do Structures Need to Be Stable?

¤ Some objects are more stable than tall ones. But tall structures are found all over the world. How do engineers design tall structures so that they are stable?

Why Do Structures Need to Be Stable?

¤ Some objects are more stable than tall ones. But tall structures are found all over the world. How do engineers design tall structures so that they are stable?

¤ Answer: The engineer who designed these structures were very useful to choose the right materials for each task. Sometimes the material was altered to make it stronger.

Materials:

¤ Sheets of paper, 21.5 cm x 28 cm

¤ Small uniform weights

¤ Pencils

¤ Hardcover books

¤ Tape

Procedure Paper Bridges Trial #1 Completed with Ms. Di Donato

¤  Divide the class into working groups

¤  Give each group

-  paper, tape, a stack of books,

-  some weights, and activity sheets

¤  Place two piles of books on a flat surface (so that each pile is the same height and approximately 20 cm apart)

¤  Place a piece of paper over the gap so it spans the two piles of book

Independently Answer Question

¤  How many weights do you think the

paper can hold before it collapses?

¤  * Show students what the weights look like

¤  * Record answer on activity sheet, titled Trial #1

Test Predictions

¤  Have the groups test out their predictions by placing weights on the paper until it buckles

¤  Synonyms for buckle: clasp, collapse

¤  * have students record the maximum number of weights their best paper bridge could support (completed as a class), draw diagram of the bridge on their activity sheets

Making Paper Towers Strong

¤ A structure is built to hold a load. The load is the weight that the structure has to support.

¤ Sometimes materials are strong enough to hold loads by themselves. Other times, materials need to be changed to become stronger.

¤ We alter, or change, the material to help it do a better job

Refer to Chart Paper

¤ What can you do to the paper so that it can support more weight?

Beams

¤ A piece of material that has to resist bending is called a beam.

¤ The shape of a beam affects how stiff it is and the load it can carry.

Keep in Mind

¤ While completing the procedure with group members, consider what can be done to the paper so that it can support more weight

¤ Refer to chart paper

Procedure Paper Bridges Trial #2 Completed with Group Members

¤  Give each group

-  paper, tape, a stack of books,

-  some weights, and activity sheets

¤  Place two piles of books on a flat surface (so that each pile is the same height and approximately 20 cm apart)

¤  Place a piece of paper over the gap so it spans the two piles of book

Presenting Group Work

¤  One member from

each group is going to present

their groups paper bridge

¤  Questions that need to be answered:

1.  What was the groups prediction for the number of weights the paper could support?

2.  How many weights was the paper bridge able to support?

3.  Show the rest of the class the drawing of trial #2’s paper bridge.

Questions for Students:

¤ Why were some paper bridges able to hold more weights than others?

¤ What was different about the paper bridges?

¤ What happened to the paper bridge when you added more weight to it?

¤ What happened when the paper bridge could no longer support the force of the weight?

What is a Force?

¤ A force is a push or pull

¤ When weights were added to the paper bridges, they pushed down on the paper. This force caused the paper to collapse.

Examples of Push and Pull Forces

Examples of Push and Pull Forces

Test Your Knowledge: Push and Pull Forces

Overall Expectations

¤  Assess the importance of form, function, strength, and stability in structures through time

¤  Investigate strong and stable structures to determine how their design and materials enable them to perform their load-bearing function

¤  Demonstrate an understanding of the concepts of structure, strength, and stability and the factors that affect them

Specific Expectations

1. Relating Science and Technology to Society and the Environment

1.1 assess effects of strong and stable structures on society and the environment

2. Developing investigations and Communication Skills

2.2 investigate, through experimentation, how various materials

2.3 investigate, through experimentation, the effects of pushing, pulling and other forces on the shape and stability of simple structures

Specific Expectation Continued

¤  2.5 use appropriate science and technology vocabulary

3. Understanding Basic Concepts

3.2 identify structures in the natural environment and in the built environment

3.3 identify the strength of a structure as its ability to support a load

3.5 identify properties of materials that need to be considered when building structures

Extensions

¤  Give students the opportunity to examine other ways that forces alter the shaper or strength of different structures.