Parade float STEM challenge: a 45-minute engineering activity, 6–8

1. Define (5 min): write the criteria on the board. The float rolls at least 1 meter past the end of the ramp, carries all 10 pennies on its deck and has a paper balloon at least 15 cm tall that stays on. Constraint: only the materials given.
2. Plan (5 min): teams sketch a design and label the axles, wheels, deck and where the load goes. Ask: "Where should the heavy pennies sit so the float doesn't tip?"
3. Build (15 min): share the most useful trick only if teams get stuck: tape a straw across the underside of the deck and slide a skewer through it, so the axle spins freely inside the straw.
4. Test (10 min): every float starts from the same mark with no pushing. Measure from the end of the ramp to where it stops. Record the distance and whether the load and balloon stayed on.
5. Improve (8 min): one change per team, then retest. Each team names the variable it changed.
6. Debrief (2 min): which changes helped most? Students usually point to straight axles, a low load and wheels that don't rub.

Science talk: connect results to friction (where the axle rubs the straw or deck) and to center of mass (why tall, top-heavy floats tipped on the ramp).

Differentiation: for students who need more support, show one working axle before building and assign roles (builder, tester, recorder). For advanced students, time the last meter of the roll and calculate speed in meters per second, then compare floats. For English learners, post a labeled sketch with axle, wheel, friction, load and stable. For students with fine-motor challenges, pre-cut the straws and skewers and let them lead testing and measuring.

Quick check: exit ticket: "Name one change that increased your distance and explain it using friction or center of mass."

If you try it, post your class's longest roll and what the winning float did differently.