Grade 5 · Design & Engineering · Lesson 138

Balance Mobile

Build a tabletop mobile with three large paper shapes that balances for 20 seconds and can move gently.

Time2 × 45 minutesTeamsPairs; alternate builder and testerEquipmentBasic classroom design materials; no powered equipment

Your project in view

What you are making

Build a tabletop mobile with three large paper shapes that balances for 20 seconds and can move gently.

This generated example illustrates one possible finished design—not actual student work. Use the lesson’s sizes, connected parts and safety steps; your colors and creative details can be different.

Generated finished-project example for Balance Mobile: Build a tabletop mobile with three large paper shapes that balances for 20 seconds and can move gently.
Balance Mobile · Generated project example

Student directions · Grade 5

What will you make and do?

Build a tabletop mobile with three large paper shapes that balances for 20 seconds and can move gently.

Teacher overview: Students will plan the specific object described below, make and test a first version, then use their results to improve it. Read one step together, demonstrate the unfamiliar action, and let students complete that step before moving on.

  1. 1Plan your project

    Draw the stand, beam and three shapes. Predict which shape or distance will make each side heavier.

  2. 2Make the first parts

    Build a broad tabletop stand. Attach the beam at one center pivot so it can tilt freely.

  3. 3Put it together

    Hang three large shapes with short strings and clips. Keep all strings below face level and off walkways.

  4. 4Test it fairly

    Release from level and time balance for three trials. Record which side drops and the seconds before touching.

  5. 5Improve one part

    Move one hanging point or adjust one shape. Repeat with the same pivot and release.

  6. 6Show and turn in

    Turn in the mobile, distance measurements and balance results. Explain how distance from the pivot changed balance.

How will you know it works?

  • Balances without touching the stand for 20 seconds
  • Shapes hang securely and move freely
  • Record the stated test and explain one revision

Before you move on

Explain which measurement, input or design choice you are testing. Predict the result and record what stays the same so your comparison is fair.

Machine cutting, printer setup and electrical power-on require adult approval. A basic-materials model is a valid way to demonstrate the design when equipment is unavailable.

Keep your plan, test notes and before-and-after evidence with the printable design brief below. Use the detailed teacher plan and any coding guide for tool instructions. These steps continue across the lesson’s meetings, not all in one sitting.

For teachers

Engineering standards

This shows how the lesson connects to the national NGSS engineering standards and what student work you can collect.

Assessed

3-5-ETS1-1

Define the need in Build a tabletop mobile with three large paper shapes that balances for 20 seconds and can move gently. Agree on the two success checks and the listed material limits.

What students show: Two labeled ideas with the target and limits stated.
Practiced

3-5-ETS1-2

Compare the ideas using the project checks: Balances without touching the stand for 20 seconds; Shapes hang securely and move freely.

What students show: A selected design with a reason connected to a success check.
Assessed

3-5-ETS1-3

Test, change one feature and retest: Release from level and time balance for three trials. Record which side drops and the seconds before touching. Move one hanging point or adjust one shape. Repeat with the same pivot and release.

What students show: Before-and-after results collected under the same conditions.

Materials

  • Cardboard stand
  • paper shapes
  • cotton string
  • craft-stick beam
  • tape
  • ruler
  • clips
  • Pencil, planning paper and the printable design brief below

Teacher preparation

  1. Gather per-pair materials: Cardboard stand; paper shapes; cotton string; craft-stick beam; tape; ruler; clips.
  2. Make one rough sample and rehearse the exact test: Release from level and time balance for three trials. Record which side drops and the seconds before touching.
  3. Set the size, load or distance marks mentioned in the steps before class. Demonstrate an ordinary first attempt, not a perfect model to copy.
  4. Prepare any holes, fasteners or difficult cuts for students. Check the stated safety note and clear the testing space.

Step by step

How to teach it

Meeting 1 · 0–8 min

See the job and plan

  1. Introduce the finished object: Build a tabletop mobile with three large paper shapes that balances for 20 seconds and can move gently.
  2. Draw the stand, beam and three shapes. Predict which shape or distance will make each side heavier.
  3. Students say what would count as a successful result.
Meeting 1 · 8–18 min

Model the unfamiliar action

  1. Demonstrate slowly: Build a broad tabletop stand. Attach the beam at one center pivot so it can tilt freely.
  2. Pause so partners can repeat the action; provide prepared parts if cutting or folding blocks progress.
Meeting 1 · 18–35 min

Build the first version

  1. Hang three large shapes with short strings and clips. Keep all strings below face level and off walkways.
  2. Partners swap builder and checker roles halfway through. Check the working part before decorating.
Meeting 1 · 35–45 min

Try once and save

  1. Run one trial of the stated test to locate an obvious problem. Do not count a changed procedure as a fair comparison.
  2. Label and store the model; sketch its current shape and clear the work area.
Meeting 2 · 0–8 min

Predict and set up

  1. Revisit the two success checks. Agree on identical starting conditions and prepare a before/after results table.
Meeting 2 · 8–23 min

Collect evidence

  1. Release from level and time balance for three trials. Record which side drops and the seconds before touching.
  2. One student operates while the other records. Swap for a later trial while noting a change of operator if it affects the result.
Meeting 2 · 23–35 min

Change one thing

  1. Move one hanging point or adjust one shape. Repeat with the same pivot and release.
  2. Keep the original results rather than replacing them with only the best attempt.
Meeting 2 · 35–45 min

Explain and clean up

  1. Turn in the mobile, distance measurements and balance results. Explain how distance from the pivot changed balance.
  2. Collect the brief and results; separate reusable materials and clean the test area.

Assessment

  • Balances without touching the stand for 20 seconds
  • Shapes hang securely and move freely
  • Student demonstrates the actual task: Release from level and time balance for three trials. Record which side drops and the seconds before touching.
  • Record includes failures as well as successes.
  • Student identifies one changed feature and uses the retest to explain the result.

Supports & extensions

  • Provide a worked first joint or sample; have students record dimensions and explain one comparison limitation.
  • Start with the smallest working version of balance mobile before decoration.
  • Extension after success: choose one more value for the same tested feature, predict its effect and repeat release from level and time balance for three trials.

Safety & responsible use

  • Teacher checks materials and test conditions before use. Use classroom scissors; adults prepare difficult cuts, holes and fasteners.
  • No powered tools, coding, hot glue or electrical circuits are required. Keep moving objects contained and test loads light.
  • Use short strings only at tabletop height. Never wrap string around the body or hang the mobile overhead.

No-machine alternative

Use prepared paper parts, larger pieces or an adult-assisted version of the same build. Keep the functional task: Build a tabletop mobile with three large paper shapes that balances for 20 seconds and can move gently. If physical testing is not possible, label sketches as predictions rather than measured results.

Printable student design brief

The challenge

Build a tabletop mobile with three large paper shapes that balances for 20 seconds and can move gently.

Success criteria

  • Balances without touching the stand for 20 seconds
  • Shapes hang securely and move freely
  • Record the stated test and explain one revision

Constraints

  • Use only the listed teacher-approved materials
  • Stay within the teacher-set size, load and test-space limits
  • Two 45-minute meetings; keep the first version simple

Engineer’s notes

Who uses this object, and what should it do?
Draw two possible designs. Label the working parts and circle your choice.
Which size, fold, gap or position must you measure or mark?
Before testing, predict what will happen: Release from level and time balance for three trials. Record which side drops and the seconds before touching.
Record each trial: condition / expected result / actual result.
Draw the ONE change you made. What stayed the same?
Record the retest. Did the change help, not help, or leave the result uncertain?
Show and explain: one result that supports your conclusion.
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