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D. Structures and Mechanisms · Materials, Objects, and Everyday Structures

Structures: Built to Hold a Load

D2.2 D2.4 D2.5 A1.3 A1.4 A1.5 A3.1About 40 minutes
Learning goals
  • I can explain that a structure is made to hold up a load.
  • I can find structures at home and in my community.
  • I can find the frame that holds up an object.
  • I can design, build and test a structure that holds a book.

Words to know

structure
An object made to hold up or support a load. A table, a chair, a shelf and a bridge are structures.
load
The weight a structure holds up. Books on a shelf are a load.
support
To hold something up so it does not fall.
frame
The inside "skeleton" that holds up an object, like the poles in a tent.
design
To plan how to make something before you build it.
stable
Steady. It does not tip or wobble.

Hold that up!

Try this: hold your arms out straight and ask a grown-up to put a pillow on them. Can you hold it? Now a second pillow?

Your arms are supporting a load!

Many objects have the job of holding things up. We call them structures.

What is a structure?

A structure is an object that is made to hold up a load. The load is the weight it supports.

  • A table holds up plates and food.
  • A chair holds up you!
  • A bookshelf holds up books.
  • A bridge holds up cars, people and trucks.
  • A bird's nest holds up eggs and baby birds.

Structures can be made by people or found in nature.

A wooden bookshelf with three shelves full of colourful books.
A bookshelf is a structure. Each shelf holds up a load of books. AI-generated image
loadlegstabletop
A table is a structure. The books on top are the load. The tabletop and legs support the load and carry it down to the floor.
🪑🛏️🌉🏠🪺⛺
Structures: a chair, a bed, a bridge, a house, a nest and a tent.

Frames hold things up

Some objects have a frame inside. A frame is like a skeleton. It holds the object up and gives it its shape.

  • A tent has poles. The poles are the frame. The fabric hangs on them.
  • An umbrella has thin metal ribs. They hold the fabric open.
  • A house has a wooden or metal frame inside the walls.
  • Your body has a frame too: your skeleton!

Take the frame away and the object falls down flat.

Strong shapes

Wide bottoms make structures stable (steady). A pyramid of blocks is harder to knock over than a tall, thin tower. Triangles are strong shapes too. Look for triangles in bridges and roofs!

Worked example

Let's decide: is it a structure?

Is a backyard swing set a structure? What is its load?

  1. Ask: Does it hold something up? Yes. It holds up the swings and the children on them.
  2. So it is a structure.
  3. The load is the swings plus the children.
  4. The frame is the metal or wooden poles. The legs are spread out wide to make it stable.

Yes. A swing set is a structure. Its load is the swings and children, and its frame is the poles.

Worked example

Let's design and build: a paper bridge

Can you make one sheet of paper hold up a toy car between two piles of books?

  1. 1. Ask: What is the problem? We need a bridge across a gap that holds a toy car.
  2. 2. Plan: Put two piles of books about a hand-width apart. Try a flat sheet of paper first.
  3. 3. Build and test: A flat sheet sags and the car falls. The test did not work. That's okay! Engineers learn from tests.
  4. 4. Improve: Fold the paper like a fan (accordion folds) and lay it across. Test again.
  5. 5. Observe: The folded paper is much stiffer. It holds the toy car!

Changing the shape of the paper made it a stronger structure. This is how engineers work: ask, plan, build, test and improve.

flat paperfolded paperIt sags under the car!Stiff! It holds the car.
Same sheet of paper, different shape. Accordion folds make the paper stiff, so the bridge holds the load.
Just for fun

Riddle: I have four legs, but I can't walk. I hold up your supper every night. What am I?

A table! It's a structure, and your supper is the load.

Hands-on activity

Design challenge: a book stand

Problem: Build a structure that holds a picture book off the table (at least as high as your hand is wide) for 10 seconds.

You may use: 10 sheets of paper or newspaper, 50 cm of masking tape (a grown-up can measure), and scissors (with a grown-up).

  1. Plan: Draw your idea first. Will you roll paper into tubes? Fold it? Make triangles?
  2. Build your structure.
  3. Test: Gently put the book on top. Count to 10. Did it hold?
  4. Improve: If it fell, what part broke or tipped? Change one thing and test again.
  5. Share: Tell or draw what worked best.

What to look for: Rolled paper tubes are much stronger standing up than flat paper. A wide base keeps it steady. Safety: test on the floor and keep fingers out from under the book.

Your turn

1

What is a structure?

2

What is the load on a bookshelf?

3

Name a structure in your home.

4

Name a structure in your community.

5

What is the frame of a tent?

6

Which is more stable: a tall thin tower of blocks or a wide pyramid of blocks?

7

Is a bird's nest a structure? Why?

More practice: warm-up

1

Does a chair hold up a load?

2

Name one structure that holds up cars.

3

What does "support" mean?

4

What are the legs of a table for?

5

What holds up the fabric of an umbrella?

More practice: on your own

1

A snowman has a heavy head. Why should the bottom snowball be the biggest?

2

Is a sock a structure? Explain.

3

What would happen to a tent if you took the poles out?

4

Your paper tower fell over in a test. What could you change?

5

What is the load on a hockey arena roof in winter?

Challenge

1

Your skeleton is a frame. What would your body be like without it?

2

Why do bridges often have triangle shapes in them?

3

Plan a structure to hold a stuffed animal up high. Name your materials and one way you will make it stable.

Check your understanding

Quiz

1.

What is a structure?

2.

What is the load on a bed?

3.

Which one is a structure?

4.

What is the frame of an umbrella?

5.

Which tower is the most stable?

6.

After a test fails, an engineer should...

For parents and teachers

Big idea: A structure supports a load (D2.2), and many objects have a supporting frame inside. This lesson also introduces the engineering design process (Strand A1.3): ask, plan, build, test, improve, share.

How to help: Go on a structure walk. Point out bridges, playground equipment, bus shelters, fences and porches, and ask "What load does it hold up?" At home, look inside a lampshade, umbrella or tent to see the frame.

About the design challenge: Let your child plan and build. Resist fixing it for them. A collapse is valuable: ask "What part gave way? What could you change?" Rolled tubes and wide bases usually succeed.

Common difficulties:

  • Calling every object a structure. Ask, "What does it hold up?" A sock or a crayon does not hold up a load.
  • Confusing the structure and the load. The load is what sits on it; the structure does the holding.
  • Frustration when tests fail. Celebrate improvements. Real engineers test many times.

Safety: Test structures low to the ground; keep fingers clear of falling books; supervise scissors.