Wheels Down Ramp Go Round and Round

People in charge: HollyJohnsen, ShelleyDeFord, MinaYoussef

Activity:

• Students build wheels (made of 2 CDs connected by a pencil as an axle. Held together with clay). Students place play-doh on the CDs in different amounts/areas to make the fastest wheel they can. At the end of class, groups race their wheels.

Concept: Rotational inertia

Materials needed:

• Play-doh
• Clay (thicker than play-doh)
• pencils (for axles)
• CDs (for wheels)
• cardboard (for ramp)

Brainstorming:

• Intro to inertia
• Mention inertia a little before beginning
• Ramp outside, and different wheels of different sizes/inertias
• Playing around with clay to modify wheels
• Races
• Share equations?
• Ice skater video and other demonstrations
• Learning how to design

Timeline: 0-10 min: Ask if anyone has heard of inertia before.

• - if yes, ask them to explain to the class - otherwise, explain Newton's law: things at rest will stay at rest, and things in motion will stay in motion, unless an outside force acts on them
  • -- ex: ice skating with little friction, and inanimate objects not moving around by themselves. -- How much does this force have to be? Depends on inertia: -- Q: If your car breaks down and you have to push it to the gas station, would you rather be pushing a huge truck/Hummer or a small VW bug? -- Q: If you were playing football, would you rather have to stop a child or a sumo wrestler?
  - There's also inertia in rotating objects -- if there were no friction, something spinning (like a top) will keep going. - Let's figure out the rules for rotational inertia.

10-15: explain activity, split into groups of 4. Go outside if possible.

• - each team gets 4 CDs, 4-5 things of play-doh, some clay, 2 pencils, a ramp.

15-35: working in groups to race their two wheels with different clay orientations to experiment with weight and placement.

35-45: convene, let each group submit their best wheel design for a race.

45-60 min: Discussion

• - Q: While building, what made it faster, what made it slower? - Q: What's important? - A: mass, radius

• If we can figure out how to download one, we'll show a clip of an ice skater pulling in her arms and spinning faster. Reduced inertia, so she can spin faster. If there's a spinny chair in the classroom, one of us can possibly demonstrate. If not, hopefully people have seen/done ice skating or played on tire swings and things and may identify.