Forces, Arch Bridges, & Truss Bridges

I’m a Christian. I was an eighth-grade American History trainer. I am currently a contract writer, public speaker, & homeschooling mom of 9.

Lesson Plan on Bridges: Forces, Arch Bridges, & Truss Bridges

This is the primary half of a two-half palms-on unit research on bridges. Activities embrace building grape and toothpick truss bridges, piecing collectively a play-doh arch bridge, appearing out the forces involved in bridge building, and more! These classes are geared towards elementary and middle faculty level kids. They had been created for a weekly homeschool co-op that meets for two 1/2 hours with 33 youngsters between the ages of 1-13. Use these enjoyable lessons along with your classroom, family, after college program, camp, or co-op!

One pupil’s drawing of a bridge

Varieties of Bridges

1. Pray. Read and focus on Ephesians 2:20.

2. Have youngsters draw a fast sketch of what involves mind once they consider a bridge.

You have to:


three. Ask youngsters to consider the final time they remember crossing a bridge. The place have been they? How were they traveling (on foot, by automobile, bicycle, bus, or prepare)? What have been their impressions? Did they discover the bridge? Ask what structures they think about to be bridges. Usually when folks think of bridges, they consider buildings spanning water.

four. Ask the kids to consider different obstacles bridges can span.

5. Introduce the five major kinds of bridges (beam, arch, suspension, cable-stayed, and cantilever) by exhibiting pictures from books. I used Bridges Are for Crossing

You have to:

a e-book akin to Bridges Are for Crossing showing the 5 major varieties of bridges (When you’d want a guide with pictures moderately than illustrations, Bridges by Seymour Simon is a good possibility.)

6. Look again on the unique drawings each child sketched. Categorize them into every kind of bridge. (Assist kids who aren’t able to establish their bridge type.) Which bridge type did most individuals think of once they considered a bridge?

(Introduction concepts came from ).

E-book I used for exercise 5

Pressure & Compression

Tension & Compression

7. Explain that bridges, like all constructed structures, rely on unseen forces that hold them together which permits them to support extra weight, also called “masses.” We normally don’t think about forces performing on an object or construction that isn’t shifting. A pressure is a push or pull on an object. When an object is at rest (not transferring), the forces performing on it are balanced.

8. Demonstration of forces:

Place a chair in the middle of the ground. Ask the youngsters whether or not there are any forces performing on this chair. Clarify that even without anyone pushing on the chair, there are forces acting on it. The pressure of gravity is pulling down on the chair. It doesn’t collapse as a result of it supports its personal weight.

Have a toddler push the chair a short distance. Ask, “What pressure simply acted on the chair?” (A push unbalanced the forces on the chair & made it transfer.)

Now have 2 kids face one another and push on both aspect of the chair so that it doesn’t move. Ask, “Are any forces performing on the chair? If that’s the case, why doesn’t it transfer?” (Although two forces are performing on the chair, they’re balanced, inflicting it to remain in place.)

This is the case with a bridge. Two forces, compression and stress, are working together in stability to maintain the bridge up at all times.

You will want:

Rigidity at work.

An instance of compression.

Learning Compression and Rigidity

9. Compression is the act of being pushed or pressed collectively. Everybody should place their arms with their palms collectively & elbows bent. Tell them to press their palms collectively. This pushing force is known as compression.

10. Clarify that stress is the act of being stretched or pulled. Have the children place their hands in front of them, and clasp curled fingertips together. Inform them to drag on their arms. This pulling force is named stress.

Beam Bridges

Beam Bridges: Compression and Rigidity

9. Give each group of youngsters a slightly damp (i.e. not rock exhausting) sponge and a marker.

One youngster ought to draw a couple of strains, about 1″ apart, on the sponge. (Don’t measure or use a ruler. Precise spacing isn’t essential.)

Have the children bend the sponge into a U-form as if a load were on it. See how the lines get nearer together on the inside of the U? That is as a result of a drive called compression makes issues shorter. On the skin of the U, the strains get farther apart. A drive called pressure makes things longer.

You will want (per group):

Kitchen sponge


10. How do these forces of compression and tension work on a bridge?

The sponge is sort of a simple beam bridge, just like in the event you put a log throughout a stream with a purpose to cross it.

Position 2 books of roughly equal height (three-four inches) 1-2 inches aside so that the flat sponge can “span” them. Put the sponge throughout the space between the 2 books.

Have one little one use a pen, pencil, or finger to put a downward force on the top of the sponge – simply enough to cause the sponge to bend however not completely collapse.

What happens to the parallel lines drawn on the top and bottom? (The strains on the highest move nearer collectively. The lines on the underside move farther aside.)

Ask where the sponge is in compression or the place the compressive forces are situated. (The inside of the U-shape/the highest.)

Where is the sponge in stress, or where are the tensile forces situated? (The skin of the U-form.)

How might you stability out the forces of stress and compression appearing on the bridge to make it stronger? (Some ideas embrace using a stiffer material for the beam, or including helps, corresponding to knitting needles or pencils, to the sponge.)

(The sponge exercise thought came from ).

Demonstrating suspension bridge compression

Demonstrating suspension bridge tension.

Compression and Pressure on Suspension Bridges

13. A suspension bridge have to be balanced to face up. It makes use of tension within the cables to create an overall power of compression in the towers. Everybody will need a associate for this exercise.

To demonstrate compression on a suspension bridge, have partners press the palms of their fingers together and lean toward each other. The kids will be making an arch with their our bodies. Go around to every pair and push on high of the arches. Explain that when you are pushing down you might be causing them to push together, or to be put into compression.

To reveal stress, have every staff member grasp the opposite’s forearms. Each kids lean again. Their arms should stretch out between them. Go around to several pairs and lean gently on prime of their arms to test their “construction”. Explain that whenever you lean on them you are pushing down and inflicting their arms to stretch, or be put into rigidity.

Demonstrating loads.

Reside Masses and Dead Masses

14. Clarify that bridges must be capable to assist two kinds of forces, called masses, or they are going to collapse. Present the toy bridge. Ask what weight it must assist. Lifeless load is the weight of the bridge itself, comparable to its columns, beams, nuts, bolts, trusses, cables, and so on. Now place the toy automobile, individual, cow, or other merchandise/objects on the bridge, and tell the kids that these are stay loads. Ask them to let you know what a reside load is. Dwell load is the burden or power of momentary exterior elements acting on the bridge, similar to individuals, automobiles, and many others.

You have to:

A toy bridge (like a block within the shape of an arch)

Examples of dwell loads (i.e. a toy automotive, toy cow, or toy individual)

15. Ask students to give you extra examples of stay load. In the event that they want hints, blow on it (wind) and shake it (earthquake). Clarify that environmental factors, resembling temperature, earthquakes, and wind additionally represent stay loads appearing on bridges. Cold and warm temperatures cause components of the bridge to vary shape and put pressure on different elements of the bridge; earthquakes push and pull horizontally on a structure as the ground beneath jerks forwards and backwards; and wind blows on a construction pushing it horizontally.

Arch Bridge Exercise Step-by-Step

sixteen. Beam Bridges and Masses:

The difference between bridge designs is how a bridge carries the burden (load). Let’s start with the most simple of bridges, the beam bridge.

For this demonstration, everybody might want to work in pairs or in teams of three.

Stand a pair of books upright like bookends, every about 6 inches aside. Have kids work in teams or pairs with one baby holding up the two books and one child including the “load” to the bridge.

Place a bit of paper throughout the primary pair. Gently place paperclips one by one in the middle of your beam bridge. At what point can it no longer maintain its load and it begins to sag?

How can you make it stronger? Let youngsters try out some theories.

17. Arch Bridges and Hundreds: The Romans came up with one resolution to this: the arch.

Have the children try to for an arch utilizing just the sheet of paper. It would collapse because its ends transfer outward.

Curve a bit of paper upward and tuck the ends contained in the e book covers to type an arch. The books are acting as abutments. What kind of pressure do the abutments (as represented by the textbooks) impose on the arch, pushing (compression) or pulling (stress)? (Answer: The abutments push again on the arch for the reason that arch is pushing on the abutments.) Level out how the stacks of books act as abutments preserving the ends of the arch from spreading apart. Gently add paper clips. Does this shape hold more of a load?

Tape 2-3 sheets of paper collectively end to finish to make 1 long piece. It needs to be as excessive because the books when it is propped up between them in an arch. Relaxation a chunk of paper on top. Can this bridge hold extra paper clips than the first 2? Why? (The arch helps to distribute weight.) (Notice: Not all teams had success with this.)

Accordion-fold a bit of paper lengthwise. Place it across the highest of the books. Fold one other piece of paper in the identical method. Lay 1 sheet of paper under and 1 sheet over the accordion-folded paper. Strive not to squish the folds. Do you suppose it will hold greater than the arch bridge? What number of paper clips can this bridge maintain before it begins to sag? The triangles in this bridge make it stronger. We’ll come back again, so keep in mind that!

You will have per group:

A pair of books

A chunk of paper


Arch Bridge Fashions

18. (In case you are not restricted by time) Divide children into teams of 6. Have three kids stand in 1 line dealing with the opposite 3 children who are also standing in a straight line, 1 behind the opposite, going through the other workforce. The center 2 children will place their palms on one another’s shoulders. The surface children should put their hands on the waist of the child in entrance of them. Once they’re set, start pushing. Push equally so everyone stays up. As quickly as you are pushed, really feel the compression (pushing) pressure that squeezes your body. That is what it is wish to be a stone in an arch bridge. Let every child have a turn in the center. The place in the middle is named the keystone. (The bridge exercise concept got here from Bridges by Carol A. Johmann).

19. Present an image of Rainbow Bridge. Have children use play-dough to form an arch bridge. Place it on its side. Minimize it into 5-7 wedge-shaped items. Try to put it together again so that it can stand up. Briefly discuss the function and significance of a keystone. (The arch bridge activity idea came from Bridges by Carol A. Johmann).

You have to per student:

Half of a container your input here of play-dough

A plastic knife

20. Make Squares and Cubes:

Start with 4 toothpicks and 4 gumdrops or grapes. Poke the toothpicks into the gumdrops/grapes to make a square with a gumdrop/grape at every nook. Poke one other toothpick into the highest of each gumdrop/grape. Put a gumdrop/grape on the highest of each toothpick. Connect the gumdrops/grapes with toothpicks to make a dice. (A cube has a square on either side. It takes eight gumdrops/grapes & 12 toothpicks.)

Use more toothpicks and gumdrops/grapes to keep constructing squares onto the sides of the dice. When your structure is about 6 inches tall or extensive, try wiggling it from side to side. Does it feel stable, or does it really feel kind of shaky?

What form could be stronger and less shaky?

You’ll need per pupil:

A minimum of 100 gumdrops, gummy fruit, or grapes

No less than a hundred toothpicks

21. Making Triangles & Pyramids

Start with three gumdrops/grapes and three toothpicks. Poke the toothpicks into the gumdrops/grapes to make a triangle with a gumdrop/grape at each level. Poke another toothpick into the highest of each gumdrop/grape. Bend these 3 toothpicks in toward the center. Poke all 3 toothpicks into one gumdrop/grape to make a 3-sided pyramid. (A 3-sided pyramid has a triangle on either side. It takes four gumdrops/grapes and 6 toothpicks.)

Use more toothpicks and gumdrops/grapes to keep constructing triangles onto the sides of your pyramid. When your structure is about 6 inches tall or extensive, attempt wiggling it back and forth. Does it really feel strong, or does it really feel type of shaky?

Why are triangles so sturdy? As you’ve in all probability already discovered, squares collapse easily beneath compression. Four toothpicks joined in a square are likely to collapse by giving way at their joints, their weakest points. A sq. can fold into a diamond.

But should you make a toothpick triangle, the state of affairs modifications. The only strategy to change the angles of the triangle is by shortening one of the sides. So to make the triangle collapse you would have to push laborious sufficient to interrupt one of many toothpicks.

Can you identify which components of the triangle are in pressure and which are in compression? (If pressure is applied to any of the corners, the 2 sides radiating from that time can be in compression, while the side reverse that point will probably be in tension. If stress is utilized to any of the edges, that aspect will probably be in tension, whereas the other two sides might be in compression.)

Are you able to add a toothpick to the sq. and rectangle so they do not transfer? (Take discover of the shapes they have made contained in the sq. and rectangle; they are triangles.)

Making trusses and assembling them to make a truss bridge

Truss Bridges

22. Building Truss Bridges: Use your gumdrops and toothpicks to build a truss bridge, which combines triangles and squares.

Place two gumdrops/grapes with their bases laying flat on your work floor. Insert the pointed ends of a round toothpick into the middle of every gumdrop’s/grape’s aspect to create a barbell shape. Insert one other toothpick to each gumdrop/grape at a 45-diploma angle. Insert each naked ends of the toothpicks into the same gumdrop/grape to form a whole triangle. Insert a toothpick into one of many base gumdrops/grapes of the primary triangle at a forty five-degree angle, and one other toothpick into the highest gumdrop/grape. Insert each of the brand new toothpicks’ bare ends into a new gumdrop/grape; this will create a second inverted triangle.

Repeat this process until you have three upright and two inverted triangles that type a trapezoidal form.

Repeat the triangle-making process to create another trapezoidal form; this will run parallel to the primary and provde the second facet of your bridge.

Connect the two trapezoidal sides of the bridge using a complete of seven toothpicks to run across from gumdrop to gumdrop.

Look down from an overhead vantage point to examine that you’ve got three squares on the base and two squares on the prime.

Painting Famous Bridges

Portray Famous Bridges

23. Permit college students to view pictures of well-known bridges. Let the youngsters sketch a famous bridge utilizing a pencil after which colour it in utilizing watercolor.

You’ll need per pupil:



24. Ask questions equivalent to:

Identify a sort of bridge (beam, arch, suspension, cable-stayed, & cantilever) What’s the definition of a power? (a push or pull on an object)

Title a power that acts on bridges. (compression, pressure, load)

Use your arms to point out me the pressure of compression. (Push them collectively.)

Use your fingers to point out me the pressure of pressure. (Pull them aside.)

What’s a lifeless load? (the load of the bridge itself, resembling its columns, beams, nuts, bolts, trusses, cables, and many others.)

What’s a reside load? (the burden or force of temporary external elements appearing on the bridge, resembling folks, autos, and so forth.)

Describe what a beam bridge would possibly appear like. (a log throughout a stream)

Describe what an arch bridge might appear like. (a bridge with arches under it)

What form can make a bridge stronger? (triangle)

What is a keystone? (The stone in the crown of the arch that holds the other stones together.)

Describe what a truss bridge may seem like. (a beam bridge manufactured from triangles and squares)

What was your favourite exercise from at this time?

Joke: Why did one bridge hope the other bridge would fall down?

As a result of they were arch enemies!

In search of More Great Books on Forces and Bridge Sorts?

Bridges by Seymour Simon – Guide picture is from amazoncom.

We additionally loved studying:

Forces Make Issues Transfer (Let’s-Read-and-Find-Out Science 2) by Kimberly Bradley (for reviewing the idea of forces)

Constructing Large by David Macaulay (particularly nice for older children)

Bridges (SeeMore Readers Level 2) by Seymour Simon

Cross a Bridge by Ryan Ann Hunter

Bridge Building: Bridge Designs and How They Work (High Five Studying) by Diana Briscoe

Bridges Go from Right here to There by Forrest Wilson

Rosita’s Bridge by Mary McMillan Fisher

Sven’s Bridge by Anita Lobel

From Cement to Bridge (Start to Finish) by Robin Nelson

Bridges by Etta Kaner

Let’s Strive It Out with Towers and Bridges : Palms-On Early-Studying Activities by Seymour Simon (great for preschool & kindergarten ages)

Bridging the World by Robert S. Cortright (for photos of well-known bridges)

Bridges of the World Coloring Ebook by Bruce LaFontaine (for pictures of famous bridges)

Would you prefer to dig in deeper with extra activities? These have many extra fantastic concepts on what to do!

Bridges! Amazing Constructions (Kaleidoscope Kids) by Carol A. Johnman

Bridges and Tunnels: Investigate Feats of Engineering with 25 Initiatives (Construct It Your self collection) by Donna Latham

Constructing Toothpick Bridges (Math Initiatives: Grades 5-eight) by Dale Seymour Publications Secondary

Draw 50 Buildings and Other Buildings: The Step-by-Step Approach to Draw Castles and Cathedrals, Skyscrapers and Bridges, and So Much Extra by Lee J. Ames

Steven Caney’s Final Constructing Ebook by Steven Caney

Build It!: Actions for Setting Up Super Constructions (Design It) by Keith Good

Material Record for the Lesson

Objects for Households to Convey Per Baby:

A pencil, marker, watercolor paints with paintbrush, & small container for water for paints

5 sheets of white computer paper (four of the pages could be scrap paper however 1 must be clear for the watercolor picture.)

Kitchen sponge (1 for each 2 children)

20 paperclips

A handful of small objects which might be heavier than paperclips (resembling pennies)

Scotch tape (1 per family)

Half of a container of play dough

A minimum of one hundred grapes, gumdrops, or gummy fruit

No less than 100 toothpicks

Protective cowl shirts (non-obligatory – we will only be using watercolor paints)

A minimum of 1 picture of a famous bridge that your baby can sketch (from a library guide, the Web, and so on.) (1 for each three kids)

Items to Deliver to Share with the Group:

A guide with pictures of the 5 main kinds of bridges

Large amount of books or other items that can be utilized for bridge span testing

Toy bridge (like a block within the form of an arch) & examples of stay hundreds (toy automobile, toy cow, toy individual)

An image of Rainbow Bridge (from a e-book or the Web), 1 plastic knife per youngster, and One piece of wax paper per child (to protect the desk)

Paper towels or napkins

Our Favorite YouTube Videos

Invoice Nye on Bridges & Forces – My kids LOVE watching Bill Nye!

World’s Biggest Arch Bridge: Hoover Dam Bridge

Ready for the Subsequent Lesson?

Build grape and toothpick truss bridges, piece collectively a play-doh arch bridge, act out the forces involved in bridge constructing and suspension bridges, paint well-known bridges, hold a bridge-building contest, and more on this enjoyable 2 half unit research on bridges!

Bridge Lesson on Forces, Arch Bridges, & Truss Bridges – That is part 1 of a 2 half hands-on unit research on bridges. Build grape and toothpick truss bridges, piece collectively a play-doh arch bridge, act out the forces involved in bridge building, and more!

Bridge Lesson on Suspension, Cantilever, & Cable-Stayed Bridges and Bridge Building Contest – That is part 2 of a 2 half palms-on unit study on bridges. Create and act out cantilever, suspension, & cable-stayed bridges, compete in a bridge-building contest, and extra!

Bridge Unit Presentations and Area Journey Ideas – This is the culminating undertaking following a 2 half fingers-on unit examine on Bridges. Also included are the sector trips we went on throughout this unit and fun recipe concepts with a bridge theme.

Searching for all of my arms-on unit examine lessons?

Enjoyable, FREE Arms-on Unit Studies – Over the years I’ve posted over 30 science and social-studies based unit research, compromised of greater than one hundred forty lessons. For every lesson I’ve included activities (with photographs), our favorite books and YouTube video clips, lapbook hyperlinks, and other sources.

© 2012 Shannon

Do you have a favorite bridge? Do you even notice them? – Or just depart a note to let me know you dropped by! I like getting feedback from you!

Shannon (author) from Florida on December 02, 2020:

Sadly, this platform would not offer that as an possibility. You may copy and paste the text into a Word document & then print it.

Lindsay Pilgrim on March 21, 2020:

Is there a printable version of this lesson?

Nasfat on October 10, 2018:

Thanks iijuan for the great effort.

Are all the lesson plans for 4th to fifth Grades? if yes do you have some for different grades,

Shannon (author) from Florida on August 24, 2012:

@digitaltree: Thank you a lot!

digitaltree on August 24, 2012:

Nice Lens and lesson on constructing bridges.

Shannon (author) from Florida on June 27, 2012:

@BikePro: Thanks for dropping by!

Graeme on June 27, 2012:

Thanks for the great article, and the Invoice Nye video! Brings me again…

ceejaycmarshall on June 12, 2012:

I love this lens! Nice unit to fit a bridge theme! Thanks.:)