D. Structures and Mechanisms · Simple Machines and Movement

Design Challenge: Build a Machine to Move a Load

A1.3 A1.4 A1.5 D2.4 D2.5 D2.3About 45 minutes

Learning goals

I can use the engineering design process: ask, plan, build, test, improve and share.
I can choose a simple machine (or two together) to solve a moving problem.
I can test my machine by measuring the force it needs, and improve it.
I can follow safety rules while I build and test.

Words to know

engineer
A person who designs and builds things to solve problems.

design
To plan how to make something before you build it.

prototype
A first model you build to test your idea.

compound machine
A machine made of two or more simple machines working together, like a wheelbarrow or scissors.

criteria
The rules for what your design must do to be successful.

Teddy needs help!

Teddy the bear wants to sit on the couch to watch a hockey game. But Teddy is sitting on the floor, the couch is high, and Teddy can't climb. (Pretend Teddy is very heavy!)

Your job: be an engineer. Design and build a machine that moves Teddy (or another load) from the floor up onto the couch or a chair, using less force than lifting straight up.

A long cardboard ramp leaning from a living room rug up to a couch seat, with a teddy bear sitting at the top and a toy car, tape and books nearby. — A simple cardboard ramp is one way to get Teddy onto the couch. What other machine could you build with things from home? AI-generated image

The engineering design process

Engineers solve problems in steps:

Ask: What is the problem? What must my machine do? (These are the criteria.)
Plan: Think of ideas. Pick one. Draw it and list your materials.
Build: Make a first model, called a prototype.
Test: Does it work? Measure the force with a rubber band.
Improve: Change one thing to make it work better. Test again.
Share: Tell others what you made, what worked and what you changed.

The design steps from this lesson. Test and Improve can loop around many times before you Share.

Simple machine idea	How it could move the load up	What you could use
inclined plane	push the load up a ramp onto the seat	a board, a big piece of cardboard, a baking sheet
wheel and axle	put the load in something with wheels so it rolls	a toy truck, a wagon, a toy stroller
pulley	pull down on a string to lift the load up	a spool on a pencil, string, a basket
lever	push down on one end of a board to lift the load	a ruler or board and a fulcrum (a block or a thick book)

Ideas for your machine

Two machines are better than one

A compound machine uses two or more simple machines together. A toy truck rolling up a ramp uses a wheel and axle and an inclined plane. Wheels make the ramp even easier to go up because there is less rubbing (friction).

Worked example

Let's follow the design process

Maya's load is a small stuffed bear with some coins in its pocket. The chair seat is about 45 cm high.

Ask: The criteria: move the bear from the floor onto the chair seat, using less force than lifting it, and the bear must not fall off.
Plan: Maya draws a ramp from the floor to the seat made from a long piece of cardboard. She will put the bear in a shoebox and pull it up.
Build: She leans the cardboard on the chair and tapes the top edge to the seat so it won't slide.
Test: Lifting the box straight up stretched her rubber band 9 cm. Pulling it up the ramp stretched it 5 cm. It worked! But the cardboard sagged in the middle.
Improve: She folds the cardboard in half to make it stiffer. She also puts the bear in a toy truck instead of a shoebox. Now the stretch is only 2 cm!
Share: Maya explains: "I used a ramp and wheels together. That is a compound machine. It needed a much smaller pull."

Maya's final machine (a ramp plus wheels) needed a 2 cm stretch instead of 9 cm. That is 7 cm less than lifting. Improving her prototype made it work much better.

Imagine this

Teddy says thank you for the machine. He also asks if the next model could have an elevator and a snack bar.

Test	What we did	Rubber band stretch
1	lifted the shoebox straight up	9 cm
2	pulled the shoebox up the cardboard ramp	5 cm
3	pulled a toy truck up the stiffer ramp	2 cm

Maya's test results

Maya's results as a bar graph. A shorter bar means a smaller pull, so the toy truck on the stiffer ramp was easiest.

Hands-on activity

Your design challenge

Problem: Move a load (a stuffed toy with a few coins or a small bag of rice) from the floor up onto a chair or couch seat.

Criteria:

It must use at least one simple machine.
It must need less force than lifting (a smaller rubber band stretch).
The load must arrive safely without falling.

You may use: cardboard, boards, books, a toy truck, string, a thread spool and pencil, tape, a rubber band and a ruler.

Ask: Say the problem and criteria in your own words.
Plan: Draw your machine and label the simple machine(s) you are using.
Build your prototype with a grown-up.
Test: Measure the rubber band stretch when you lift the load straight up. Then measure it using your machine. Record both.
Improve: Change one thing. Test again.
Share: Show your drawing and results. Tell what you would change next time.

Safety rules:

A grown-up does any cutting.
Build on the floor or a steady chair. Do not stand on furniture.
Keep string away from necks. Do not stand under a hanging load.
Pull rubber bands gently and point them away from faces.
Clean up when you finish.

Your turn

What are the six steps of the engineering design process?

What is a prototype?

What is a compound machine?

Name a compound machine.

Your machine stretched the rubber band 4 cm. Lifting stretched it 8 cm. Did your machine meet the "less force" criteria?

Why do engineers draw a plan before building?

Name two safety rules for the design challenge.

More practice: warm-up

What does an engineer do?

Which step comes right after test?

Could a ramp help move a load up onto a chair?

What tool do we use to measure the rubber band stretch?

Is it okay if your first test does not work?

More practice: on your own

Ella's ramp was too steep, and the load kept sliding back. Name one way to improve it.

Why should you change only one thing at a time when you improve?

Leo used a spool pulley. His rubber band stretched the same as lifting. Did it meet the criteria? What could he try?

Maya's stretches were 9 cm, 5 cm and 2 cm. Which test needed the most force? The least?

How could you share your design with your class?

Challenge

Design a lever to lift a heavy book a little bit off the table. Where would you put the fulcrum, and why?

Your ramp works, but it takes up the whole room. How could you change the design and still use less force than lifting?

A wheelbarrow is a compound machine. Explain how each of its simple machines helps.

Check your understanding

Quiz

What is the first step of the engineering design process?

What do engineers do after they test?

A toy truck rolling up a ramp is a compound machine. Which two simple machines does it use?

Your machine stretched the rubber band 3 cm. Lifting stretched it 9 cm. What does this show?

Which is a safe choice during the build?

A prototype is...

For parents and teachers

Big idea: This lesson uses the engineering design process (A1.3): ask, plan, build, test, improve and share. Your child chooses simple machines for a task (D2.3, D2.4), measures force with and without the machine (D2.5), follows safety rules (A1.4) and shares results (A1.5).

How to help: Let your child lead the planning, even if you can see a problem coming. A test that "fails" is a great learning moment: ask, "What happened? What could you change?" Help with cutting and with holding things steady.

What success looks like: a labelled drawing, a working prototype, two or more measurements, one improvement, and a clear explanation. The machine does not need to be perfect.

Common difficulties:

Changing many things at once. Encourage one change per test.
Expecting a fixed pulley to reduce force. Remind them it changes direction only.
Measuring unevenly. Pull slowly and steadily, and read the ruler while the load is moving.