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Engineering activity

Rubber Band Racer

Build a simple car from a cardboard tube with straw axles and bottle cap wheels, powered by a rubber band!

BuildingAbout 25 minutesScreen-freeParent help expected

Materials and setup

How this changes by age

Pre-K (ages 3–4)

Build a simple car from a cardboard tube with straw axles and bottle cap wheels, powered by a rubber band!

Difficulty 1 of 3

Steps

  1. Build a rubber-band car: poke two straws through a cardboard tube for axles, attach bottle caps as wheels, and loop a rubber band around the rear axle.
  2. Wind the rubber band by turning the rear wheels backward, then let go.
  3. Roll the rubber-band car. Where does it stop? Mark it with a piece of tape on the floor.
  4. Try again — does it stop in the same place?
  5. Tell a grown-up one thing that surprised you.

Learning objectives

  • Discover that a wound rubber band stores energy that can make things move
  • Build a simple vehicle with axles and wheels
  • Observe cause and effect with stored energy release

Kindergarten (ages 5–6)

Design and build a rubber band car that rolls at least 3 feet. Experiment with wheel size and rubber band thickness.

Difficulty 2 of 3

Steps

  1. Build TWO rubber-band cars from cardboard, straws, and bottle caps. Make them as similar as possible.
  2. On the first car, wind the rubber band MANY times (e.g., 15 wraps). On the second car, wind it FEWER times (e.g., 5 wraps).
  3. Race the two cars side by side from the same starting line. Which one goes farther?
  4. Mark where each car stops. Measure the distance.
  5. Talk about it: why might more wraps make the car go farther? (Hint: more stored energy.)
  6. Tell a grown-up one thing that surprised you.

Learning objectives

  • Build a vehicle that converts stored energy into motion
  • Compare how wheel size affects travel distance
  • Measure and record distances from multiple test runs

Early elementary (ages 6–8)

Engineer a rubber band car optimized for distance. Test variables including rubber band winds, wheel size, and surface friction. Record data systematically.

Difficulty 2 of 3

Steps

  1. GOAL: Design a rubber-band car that carries a small toy 'passenger' 30 feet without the passenger falling off.
  2. Build a sturdy car frame with axles and wheels. Ensure wheels spin freely. Add a flat platform or seat for your passenger.
  3. Test: place the passenger, wind the rubber band, release. Did the car reach 30 feet? Did the passenger stay on?
  4. Measure the distance traveled and count successful trips (passenger still aboard at 30 feet) out of 5 attempts.
  5. Iterate: if the passenger flies off, lower the seat, add a seatbelt (rubber band), or smooth the ride. If the car doesn't reach 30 feet, reduce friction or add more winds.
  6. Record your best result: distance + number of successful trips out of 5.
  7. In one sentence, tell a parent or sibling what surprised you today.

Learning objectives

  • Conduct controlled experiments changing one variable at a time
  • Understand the relationship between stored energy and distance traveled
  • Analyze how friction from different surfaces affects vehicle performance

Upper elementary (ages 8–10)

Design a rubber band vehicle optimized for either maximum distance or maximum speed. Calculate potential energy stored in the band and compare to kinetic energy of the vehicle.

Difficulty 3 of 3

Steps

  1. GOAL: Design a rubber-band car that carries 100g of cargo. Optimize for EFFICIENCY, not raw speed.
  2. Build a vehicle with low-friction axles, aligned wheels, and a cargo platform that holds a 100g weight (a small bag of coins or rice).
  3. Measure SPEED: time how many seconds the loaded car takes to travel 30 feet. Run 3 trials and average.
  4. Measure EFFICIENCY: cargo grams (100g) divided by the number of rubber-band wraps used. Higher ratio = more efficient.
  5. Iterate: try fewer wraps with better wheel alignment, lighter frame, or larger wheels. The goal is to move the cargo with the FEWEST wraps possible.
  6. Compare version 1 vs version 2. Which had a better grams-per-wrap ratio?
  7. Report your best efficiency ratio (cargo grams per rubber-band wrap) and your 30-foot time.
  8. In one sentence, tell a parent or sibling what surprised you today.

Learning objectives

  • Calculate and compare potential and kinetic energy in a mechanical system
  • Identify sources of energy loss in a vehicle (friction, drag, misalignment)
  • Optimize a design for energy conversion efficiency

Safety and evidence note

Read the full activity before beginning. An adult should supervise tools, heat, food, outdoor work, movement, and experiments as appropriate. Completion records that the activity was done; the child’s explanation, work sample, photo, or demonstration is stronger evidence of learning than a completion check alone.

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