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STRUCTURES AND FORCES

Welcome to STRUCTURES AND FORCES

1st ESO

GLOBAL GOAL: develop spontaneous talk between learners

Learning outcomes (what learners will be able to do by the end of the lesson)

Describe with the aid of written, audio-visualor digital information, the main characteristics of a structural type.

• Relate efforts with structures and explain how they work.
• demonstrate understanding of the concept of force and its related features.
• successfully engage in visual matching between concepts and images.
• use language creatively.
• use a class vocabulary record of new words.

Lesson 1: Introduction and activation of previous concepts. Structures.

 Students will know about… Learning Resource or Activity Description Classroom and materials Previous concepts about structures.. Presentation  Sharing previous concepts through questions, brainstorming. warm up: video  https://www.youtube.com/watch?v=jh3wLR-bG-I Activation of previous concepts on internal forces and structures. -    Theory/computer classroom. -    Digital whiteboard. -    Worksheets. -    Notebook. Previous knowledge activity: KWL chart. Starting a KWL chart.(What I Know/What I Want to know/What I Learned) Task 1: classify structures. In groups, students will classify structures (drawn on flashcards) whether they are natural or man-made. Then will explain conclusions to the rest of the class. Task 2: key Words activity. Students in groups will identify the ten main words of the transcription of the video.  After, the whole class will debate which are the most important words. With this activity students start a glossary. Final task: One minute paper. Brief activity to summarize main concepts.

Lesson 2: Forces and structures.

 Students will know about… Learning Resource or Activity Description Classroom and materials Forces and structures. Conditions of structures: rigidity, resistance and stability Starting routine: what can you remember? Questions to review concepts of previous lesson. -   Computer classroom. -   Digital whiteboard. -   Worksheets. -   Notebook. Video about structures conditions. Activity 1: Describing structures. Hand-out (speaking, drawing and writing activity) + pair work. One student will describe a structure, the other student will draw it. Then students switch places. Hand-outs will include descriptions. Activity 2. Thinking activity. Conditions of structures: rigidity, resistance and stability. Teacher describes a structure. Learners fill in a table. Then, the whole class decide which structures are resistant, rigid and stable. After that, teacher checks their comprehension. Task 2: Talking about forces and efforts: https://www.youtube.com/watch?v=uoKo3DbfYZk Video about forces and efforts. Activity 1: How many forces do you know? In groups, students will draw a structure. They will decide which forces affect the structure. Next, students will explain the rest of the class how the structure works. Activity 2: answer questions. Students will answer questions. Ending the lesson. Glossary Time to think about new words which learners don't know.  Words are written on the board and revised by the teacher.

Lesson 3: Structural types.

 Students will know about… Learning Resource or Activity Description Classroom and materials Structural types. Starting routine what can you remember? -  Computer classroom. -  Digital whiteboard. -  Notebook. Task 1: Introduction and online activity: http://uk3.hotpotatoes.net/ex/163166/PDVDOZOG.php Introduction of main concepts and online activity. fill in the blanks activity. Video about a famous structure. Ending the lesson: Debate. Which type of structure is stronger in terms of rigidity, resistance and stability?

Lesson 4: efforts, materials and shapes.

 Students will know about… Learning Resource or Activity Description Classroom and materials Structural efforts: traction, compression, torsion and shear. Materials and structures. Shapes and structures. Triangles in structures. Starting routine: what can you remember? Questions -  Computer classroom. -  Digital whiteboard. -  Notebook. Task 1: Introduction and video on efforts: https://youtu.be/8IN544ZKzmQ Explaining basic concepts about efforts. Activity 1: Forces on-line lab: vocabulary ad technology activity. On-line lab that simplifies the real-life forces and actions that affect structures. Activity 2: Online activity. http://uk3.hotpotatoes.net/ex/163166/SWCKQTXT.php Online match activity about structures and efforts. Task 2: watch the video: https://youtu.be/oVOnRPefcno Video about bridges. Activity 1: What makes bridges so strong? Fill in the blanks. Activity 2: Materials on-line lab :http://www-tc.pbs.org/wgbh/buildingbig/lab/swf/materials.swf On-line lab that simplifies the real-life properties of a selection of materials, in order to illustrate key concepts. Activity 3: Shapes on-line lab: http://www-tc.pbs.org/wgbh/buildingbig/lab/swf/shapes.swf On-line lab that simplifies the conditions that affect structures (shapes), in order to illustrate key concepts. Ending the lesson: playing with structures. Different on-line applications and games where students intuitively will handle with structures.

Lesson 5: Theory assessment.  Mini-project.

 Students will know about… Learning resource or activity Description Classroom and materials Synthesis task Task 1: multiple option test. http://uk3.hotpotatoes.net/ex/163166/HQHPVCIZ.php Individually students will carry out a task in the computer to check what has been learned throughout the unit. The task will be evaluated. -  Computer classroom -  Notebook. -  Mobile video camera. Task 2: Mini-project. An outstanding structure Activity 1:  choose structure and answer questions. This task will start after the theory assessment. The task will take 3 lessons. During this lesson, students choose a structure. Then will answer some questions.

Lesson 6 and 7: Mini-project.

 Students will know about… Learning resource or activity Description Classroom and materials Synthesis task Activity 2: Drawing/construction. Gathering information with critic criteria. Video report. Students will prepare, drawings, models, photos, etc. about the structure.  All the work should be compiled in a video report with explanations. Internet can be checked in order to get information for the project. -  Workshop -  Notebook. -  Mobile video camera.

Lesson 8: Exhibition of works and evaluation

 Students will know about… Learning resource or activity Description Classroom and materials Description of a structure: elements, efforts,  way of work… Task 1: Presentation of works. Videos will be projected. The presentation should include explanations, pictures, drawings, model etc. Evaluation will be made both by their classmates and the teacher. -  Theory/computer classroom. -  Digital whiteboard. -  Notebook. Task 2: reflexion activity. Students will complete the KWL chart that they will started at the beginning of the unit.

REMEMBER: write on your notebook a list of new terms and concepts which can help you; you can also write those terms you think are important to remember.

REMEMBER: you have to write an everyday reflection on your blog/notebook, answering the following questions:

• What have you learned today?
• How have you learned today?
• Have you worked alone or in groups?
• What new terms and concepts in English have you used today?
• In which point of the class did you have a problem?
• How did you find a solution to that problem?
• Do you have any other doubt about the lesson?

LESSON 1: INTRODUCTION AND ACTIVATION OF PREVIOUS CONCEPTS.

Warm up: general overview of the unit (video)

Transcription:

Good morning scientists as we continue our unit on structures today we are going to look at various man-made and natural structures what do you think of when you hear the word

structure people often think of buildings when they hear this word and mostly famous once but not all structures are buildings structures are all sorts of things a desk home a vehicle bed

and even a mailbox structures do many things they provide warmth they do things hold things some structures are gathering places some tell a story some structures are a part of society

and some structures are landmarks some structures are just nice to look at some structures are man-made that means people made or built them such as cars houses mailboxes or

buildings but sometimes nature provide us with structures these structures are found naturally in the environment and they are not made by people sometimes forces such as erosion

make natural structures beehive tree nest and Hill and even the Grand Canyon are all examples of natural structures turn to your partner and tell them if this structure is a man-made or

natural structure tell your partner what the structure is made up an igloo is an example of a man-made structure even though is made from something found in nature this is a

picture of Mount Everest is it man-made or natural what do you think it's made of this is an example of a natural structure this is a picture of a well-known bridge found in San Francisco

is it man-made or natural this structure is definitely man-made do you think the structure is man-made or neutral this is Stonehenge and it's made of stone which is part of nature but

people oved and piled the stones while we are not sure how it was done we know nature cannot arrange stones this way so this is an example of a man-made structure

sometimes things found in nature inspire people take this beaver dam for example the beaver dam is an example of a natural structure while the dam on the right is clearly a man-made

structure thank you scientists keep asking questions and keep investigating.

Previous knowledge: starting a KWL chart (What I Know/What I Want to know/What I Learned).

What I Learned

The final column will be completed at the end of the unit and it will serve both students and teacher to check if student´s expectations have been fulfilled.

Flashcards with structures drawn on them will be given to each group. After a chat, each group will decide which structures are natural or man-made. Their conclusions will be shared and explained to the rest of the class.

Students in groups will read the transcription of the video and they will identify the ten main words of the text. After some minutes of reflexion the whole class will debate which are the most important words. The words will be written on the board (with this activity students start a glossary).

As surely there will be more than 10 words, the task will consist in reducing the number of words. Each word will be considered individually by the group which proposed it which will have to justify his decision. In many aspects this will be the more useful part of the exercise.

- Ending the lesson: One minute paper. Brief activity to summarize main concepts

LESSON 2: FORCES AND STRUCTURES

starting routine: what can you remember?

“Is the hospital a natural structure? Why?”

“Can you name an example of man-made and natural structure?”

Ever wonder how tall buildings can withstand windy days, or why bridges don't collapse when large trucks drive over them? The answer is structural engineering. Structural engineers use physics and math to design and analyze the sturdiness of structures, things like bridges, buildings, concert stages, and even rollercoasters. Don't get me wrong. Designing any one of these things can involve multiple types of engineering, but it's structural engineering that's responsible for making sure that that structure won't collapse or fall over. You see, a structure must be able to handle the forces or loads that it's likely to experience. Take a skyscraper, for example. It not only has to support itself, but also all the people and furniture inside the building, and then external factors, like wind, snow, or an earthquake.

The materials and geometry that make up a structure influence how it may respond to those forces. Different materials have different properties, like strength, weight, and flammability, that can influence a structure's sturdiness. For example, steel is generally stronger, and weighs more than wood, and different geometric shapes work better for different purposes. For example, a square or rectangular base can typically hold more weight than a triangular base. Structural engineers perform calculations to determine the best materials and shapes to use in order to build a study structure. The next time you find yourself at the top of a rollercoaster, you can thank structural engineers for doing their part to make sure it's nice and sturdy.

Activity 1: Describing structures. Hand-out (speaking, drawing and writing activities) + pair work. One student will describe a structure, the other student will draw it. Then students switch place and start again. Hand-outs will include descriptions. Any misunderstood word will be looked up in the dictionary.

Teacher will introduce structural concepts like rigidity, resistance and stability with pictures and drawings.

Activity 2. Thinking activity: Conditions of structures: rigidity, resistance and stability. Teacher describes a structure, naming each element. Learners fill in a table on their notebooks. Then, the whole class has to decide which structures are resistant, rigid and stable. After that, teacher checks their comprehension. Drawings will be collected for later assessment.

Sketch

Transcription:

A force is a push or pull we can't see a force but we can see the effects of a force

A force:

1) can move the stationary object

2) stop moving an object

3) or change its direction

A force...

4) can change the speed of the object.

5) it can also change the shape of the object.

A force is mesure using a force meter.

The SI unit of force is Newton.

There are two kinds of forces: contact force and non-contact force

When we push or pull an object, we have applied force to the object.

The object will move in the direction of the applied force.

An applied force is an example of a contact force.

Friction is also a form of contact force. Friction goes against motion eventhough friction slow things down and makes movement difficult

there are many things we could not do without friction,

Friction holds us to the ground and allowing us to walk without slipping.

Friction causes a car brake in time to accidents

The amount of frictional force depends on the texture of surfaces in contact

When the surface is smooth there is less friction.

The force that makes things fall to the ground is called gravity.

Gravity is an example of non-contact force.

Gravity pulls an object to the earth.

The force of gravity also exists on the moon but it is not as strong as it is on the earth.

When an object rests on an surface there will always be a reaction force.

When we're standing on the earth the reaction force balances the weight of our body so we don't fall through the pavement.

The reaction is also called normal force.

Magnetic force is a non-contact force

Magnetic force only acts on magnetic objects ....iron, steel and nickel are magnetic materials.

The force of magnetic attraction pulls the magnetic objects towards the magnet.

The interaction of forces makes the world we live in the way it is.

A cycle on a bicycle experiences the interaction of different forces:

1) gravity pulls the weight of the bicycle and the rider towards the earth while an equal reaction force acts upwards.

To manage gravity as you ride the frictional force between the wheels of the bicycle and the ground acts against the forward force so you

don´t go too fast.

As a fish swims forward water resistance acts in the opposite direction

When gravity pulls the fish towards the bottom of the water the upthrust exerts an upper force that encounters gravity.

In level flights the upward lift apply to the wings of an aeroplane equals to the amount of weight of the plane.

When a force forward thrust the fella is equal to the air frictional drag on the plane

Activity 1: How many forces do you know?

In groups of four, follow the next steps...

1. Draw on a paper a structure. It can be a bridge, a house, a skyscraper, a tower from the middle ages, a building, whatever.... Don´t take too much time drawing, it´s just a sketch.
2. Once it is done, talk with your partners and draw in different colours all the forces that you think might affect the structure: weight, wind, earthquake… think how each force behaves.
3. Now you are going to tell the rest of the class how your structure works.

Activity 2: Now, split the groups in pairs and answer these questions:

• Think on three different situations where forces are used in your everyday life.

• Draw the forces affecting the bicycle and the rider

• Have you ever been on a plane or diving? Draw a plane or a diver and the forces. Talk to your partner and try to explain him how forces affect you in any of these situations.

Ending the lesson. Glossary. Time to think about new words which learners don't know.  Teacher writes new words on the board.

Homework: Let´s look for structures!

Individually, students will look on the internet for different types of structures. They will write them on their notebook for later revision.

LESSON 3: STRUCTURAL TYPES

Starting routine: what can you remember?

Questions:

• “Is push and pull a force?”
• “what are the main conditions of structures?”
• “definition of rigidity, resistance and stability"

Now, we know a little bit more about forces. It´s time to see different kinds of structures.

1. Massive structures

2. Shell structures.

3. Trusess.

4. Frame structure.

5. Suspension structures.

Now, we will watch the following video:

Task 2: Fill in the blanks

Hi, I'm Veronica jolla california travel tips here outside the glorious golden gate bridge in San Francisco.

Let's learn a little bit more about the golden gate bridge. Its history, architect and some little-known facts.

The Golden Gate Bridge history dates back to its proposal in 1916.

Construction began in _____ and 35 million dollars later, the bridge officially opened to traffic on May 28 ______

It was the ______ suspension bridge in the world until ______ the record has been beaten several times.

Since then as we passed through the _____ gate began our crossing by car.

I wondered how long is the golden gate bridge.

We learned it's about 1.7 miles from _________ to ____ with a 40 200-foot _________ span

Engineering ________ marvel at the Golden Gate Bridge blueprints _______ by joseph strauss in irving morrow.

Until then it was called the bridge that couldn't be ______ due to rough ocean currents, heavy fog and 60 mile-per-hour winds.

The vista point on the Marin County side is the ______ place to stop and _____   ______ of the Golden Gate Bridge.

Enjoy the city's fabulous ______ through a viewfinder or marvelous this beautiful piece of American ________

I hope you enjoyed this quick Golden Gate Bridge _______   _____.

I learned some _________facts about the golden gate bridge and I hope you did too

______ veronica hill and that's your California travel tip.

Ending the lesson. A debate about structural types will be created.

DEBATE GUIDELINES:

• Each group will choose a structural type and discuss PROS AND CONS.
• Brief presentation of arguments.
• Whole discussion and conclusion.

Debate Topic: Which type of structure is stronger in terms of rigidity, resistance and stability?

LANGUAGE SCAFFOLDING:

Definitions:

MASSIVE: Structure made by piling up similar materials into a particular shape or design. It was commonly used in ancient times to build the pyramids.

FRAME: Skeleton of vertical and horizontal elements: beams, pillars and columns that support the weight of other elements. They are ussually made of reinforced concrete and steel.

TRUSSES: Frame structures formed by triangles. The triangle is the most rigid frame structure.

SUSPENSION: Structures in which the main elements that support the load (wires and cables) are subject only to forces of extension.

SHELL: A type of structure made up of layers of materials bound together to form complex shapes or to produce a material with high strength for its weight. They are used in computer´s boxes, cars or aeroplanes.

BEAM: Beam is a flexure member of the structure. It is subjected to transverse loading such as vertical loads, and gravity loads. These loads create shear and bending within the beam.

COLUMNS: A long vertical member mostly subjected to compressive loads is called column.

STRUT: A compressive member of a structure used in refurbishing.

GRID: A network of beam intersecting each other at right angles and subjected to vertical loads is called grid.

CABLES AND ARCHES: Cables are usually suspended at their ends and are allowed to sag. The forces are then pure tension and are directed along the axis of the cable. Arches are similar to cables except hath they are inverted. They carry compressive loads that are directed along the axis of the arch.

Vocabulary:

prepositions of place:

At the top/bottom...  In the middle there is...                     On the left/right ...

next to…             in front of…                      behind…              near…    on top of…

under…

Expressions:

We think/We believe....

________ are stronger than __________ because...

________ are more rigid than _________ because ...

________ are more stable than ________ because....

________ are more resistant than ______because...

Some examples:

Massive structures are stronger than  frame structures because they are made of _________________.

It is more resistant because it has _________________.

It is more stable than __________ because it is wider on the base and narrower at the top.

LESSON 4: EFFORTS, MATERIALS AND SHAPES.

Starting routine: what can you remember?

Questions:

“Is push and pull a force?”

“Is traction originated by a vertical force?”

“Is a pyramid a massive structure?”

“Is a tree an artificial structure?”

Task 1: In this video you will understand the different kinds of efforts and how are related with forces.

We can also work this part with play dough, writing key words on the board and telling students to copy them on their glossary.

Activity 1: Forces on-line lab: vocabulary ad technology activity.

On-line lab that simplifies the real-life forces and actions that affect structures, in order to illustrate key concepts.

http://www-tc.pbs.org/wgbh/buildingbig/lab/swf/forces.swf

In pairs, click on the "FORCES LABORATORY" button. Write your conclusions on your notebook

Activity 2: Online activity.

Click on FORCES AND STRUCTURES button. Write your conclusions on your notebook.

Activity 1: Fill in the blanks.

TV presenter: hi guys, I were just playing with some blocks. You know it may not seem like it but the cities and towns that we live in are all built using the same rules as our little pretend

village over here. It's just that the real ones are bigger and one of our viewers six-year-old.

Hannah from the UK want to know how some of the things that we build stay standing. So she sent us a really great question:

why our __________ so strong?

Excellent question.

Sometimes when a road or rail road track needs to go across something big like a _____ or a deep ______ experts called __________ design and build bridges to do that job and bridges

can be really busy.

Take for example, what's said to be the world's busiest bridge the George Washington Bridge in ________________ City.

Look at all those cars and _______ it has to be pretty sturdy to carry so many people and cars for a bridge. To carry that much weight it has to be built a special material like _____ and

_______ but it takes more than tough materials to make a _______ bridge.

So let's look at how bridges work one very simple kind of bridge is called a _______ bridge.

When we say simple we really do mean simple a beam bridge can be just a log that used to walk across the street or put a long strip of cardboard between two short blocks

that's a beam bridge to all bridges can hold a certain amount of weight but what happens if we put too much _______ on a beam bridge let's find out it __________ so bridge that carries

trucks and cars which are very heavy would have to be stronger than a bridge that carries bikes or people on foot which are lighter so how do we make _________ bridges? well over

time people have learned that certain shapes can be used to make stronger bridges.

Take a look at this railroad bridge it has to be strong because it carries trains what shape do you see?

that's right _________ and that's not by accident the fact is triangles are really strong _________ for building if you put force on one side of a triangle it bends, but if you put ______ on

its point, it keeps its ________.

That's because the two sides of the triangle or push down by the ______ and the bottom gets stretched out to both sides each side feels the force but none of them _______ and this

makes the triangle or really sturdy and stable shape.

This is why you'll see lots of triangles and bridges both above the part that you actually travel on called the deck and below it the long string of triangles that you see in a bridge is called a

truss.

Truss has helped a bridge spread out the weight that it has to carry but not all bridges are made of _________. If a bridge has to cross a really _______ body of water it might be too

difficult or expensive to build a truss bridge so engineers design another kind of bridge called a ___________ bridge The ______________ bridge in California is a great example of a

suspension bridge.

Suspension bridges work by using a force called ____________. Tension is just pulling something tight.

Suspension bridges are made of a _________ that's hung or suspended from thick ________ that stretch from one side of the bridge to the other.

These cables are supported by _____ towers and then are held down tightly or anchored on both ______.

Suspension bridges are strong because the force on the bridge gets spread out. The ______ of the cars or trains horses whatever is traveling across it pulls on the cables creating

________. Both cables then pull _____ the towers and also pull ___ the anchors on either end of the bridge to hold up the deck.

I could go on and on about all kinds of _______ bridges but basically bridges are strong not only because they're made of _______ materials but also because of the smart

_______ dreamed up and planned by ________ so thanks for asking Anna and thank you for hanging out with us at scishow kids.

See you next time

Activity 2: Click on the "SHAPES LABORATORY" button.

Activity 3: Click on the "MATERIAL LABORATORY" button.

Ending the lesson: playing with structures. Different on-line applications and games where students intuitively will handle with structures.

LESSON 5-6-7: ASSESSMENT. MINI-PROJECT

Task 1: multiple option test. Individually students will carry out a task in the computer to check what has been learned throughout the unit. The task will be evaluated.

Click on the MULTIPLE OPTION button.

Task 2: Mini-project. An outstanding structure.

Activity 1: In groups, students will choose a structure (internet might help them). Then, they will search for the information needed to answer some questions.

Questions:

What type of structure is it?

What is its function? If it is a bridge, a building, an object, etc.

How can the structure withstand windy days?

What types of forces does this structure support?

Are there any tension effort? Compression effort? Bending effort? Torsion effort?

Which elements stand the weight?

How is weight transmitted to the ground? Describe the process.

What would happen if a pillar or beam is removed?

What would happen if we add more weight?

Activity 2: Students will prepare, drawings, models, photos, etc. about the structure.  All the work should be compiled in a video report with explanations.

GUIDELINES:
• Find a structure in the internet.
• Make a detailed drawing of the structure. Including the name of the elements (pillars, columns, beams, cables, etc.).
• Draw the forces that affect the structure.
• In case you want to make a model of the structure, a simple sketch will be enough. The model should be made with paper, chopsticks, glue, carton, etc.
• Write on your notebook the answer for the questions written above.
• Record a video using a mobile phone to compile: all the information about the construction process, explanations and information of the structure, forces and efforts, structural type, structural conditions: rigidity, stability, resistance. And answer to the mentioned questions. You may include all the information that you can get from the internet about your structure and think it is valuable.
• Videos will be projected in the last lesson for assessment.

Example given: Golden Gate Bridge of San Francisco.

Questions:

What type of structure is it? It is a pendant structure.

What is its function? It is a pendant bridge so it connects both sides of San Francisco´s bay. Cars and trucks can pass from one side to the other.

How does the structure withstand windy days? The platform is supported by cables. These cables are supported by two towers. The towers are anchored on both sides of the bay with strong cables and reinforced concrete foundations.

What forces can support this structure? Horizontal and vertical forces.

Are there any tension effort? Yes there are. Cables support tension efforts.

Are there any Compression effort? Yes, there are. The towers support compression efforts.

Are there any Bending effort? Yes, there are. The platform is a big truss which supports a bending effort.

Are there any Torsion effort? Yes, there are. The trusses also support torsion efforts created by the wind or an earthquake.

Which elements stand the weight? Trusses, metallic towers and cables.

How is weight transmitted to the ground? The towers support the majority of the weight. The weight of cars and trucks are supported by the trusses and the trusses are supported by the cables, which transfer the effort to the towers. The towers then dissipate the compression directly into the earth.

The supporting cables, on the other hand, receive the bridge's tension forces. These cables run horizontally between the two far-flung anchorages. Bridge anchorages are essentially solid rock or massive concrete blocks in which the bridge is grounded. Tensional force passes to the anchorages and into the ground.

What would happen if a pillar or beam is removed? If a tower is removed the bridge would fall down.

What would happen if we add more weight? Probably the bridge would stand, but it has a limit.

Once the drawing is finished, you can check if the structure has any of the shapes we studied on the previous lessons.

Besides, you can check if there is any of these basic structural steel shapes.

Explain all the information on your video.

Language of learning

Review of all the vocabulary studied

Language for learning

Language for classifying:

This structure is a …………… structure. It is a …………. structure because it ………… This structure has three features: …………………..

Example:

This structure is a pyramid. It is massive structure because it is made by piling up similar materials into a particular shape or design. Pyramids were commonly built in ancient times.

Language to describe / analyse:

This structure is stable, rigid and resistant.

This structure has three features: rigidity, resistance and stability.

It is stable because when you apply a force it doesn´t move.

It is instable because when you apply a force it can collapse.

The platform is supported by............

The weight is supported by the ................

Language for comparing and contrasting:

More …………….. than …………….. Less……………….than…………….

This structure is more rigid than a wooden house.

It is more stable than a pendant bridge but less stable than a frame structure.

Language to communicate ideas and opinions:

I think / I believe that …. ……..Although it is not ……..

I think that San Francisco pendant bridge is a stable and resistant structure. Although it is not as rigid as a pyramid because it moves when wind blows.

Language to hypothesize:

If ……………………… are removed …………………….

If we add ……………………the structure might ………….

Examples:

If some cables are removed the bridge might fall down.