$5 Hovercraft

Here's a cheap CHEAP way to demonstrate a batch of fizzix concepts in a really fun way. A student hovercraft can demonstrate Uncle Newton's Laws, air pressue, vacuums, Uncle Bernoulli, friction, center of mass/weight, conservation of momentum, and that learning actually can be fun and dangerous at times!

I got this particular design from fellow Fizzix Fixture, Harry Rheam, of Eastern High School in Voorhees, NJ. He got a batch of us together about 14 or 15 years ago at Glassboro State College, now named Rowan University, and shared some of his neat ideas. Harry is one of the Demi-Gods of Fizzix teaching! Visit him at... For the complete construction directions, here's the Word DOC format and here's the Adobe PDF format.

Notice, mine uses the top of an old ShopVac, only 1.5hp. You don't need much.

So, what to do with this thing?

  1. Easiest thing is just to ride it! It will skim across the floor almost resistance free. A few things to note while it is moving;
    1. It ALWAYS moves in a straight line, verifying Uncle Newt's 1st Law. No matter what the kids do to it, it won't "curve".
    2. Also along 1st Law stuff: when pushed, give it a little torque also. This will allow it to rotate while linearly moving. Note the rotation continues as well as the linear motion until crashing into a wall or a standing student's ankles.
    3. Have a kid sit "off-center" and apply a pushing force diametrically. The craft will rotate around it's center of mass which the observers can readily see.
  2. Conservation of Momentum:
    1. I have a kid "foating" stationarily on the craft. Then I throw an old medicine ball, weight 15 LBS, directly at him so he catches it. This exemplifies an inelastic collision - a concept that sorta escapes most average kids for a while. The recoil of the catcher and craft is MORE than obvious.
    2. After the kid is stabilized again, he throws the medicine ball at me. The observers will note that he recoils again. Most kids will immediately place all those ugly equations in the back of their minds and actually "see" what Conservation of Momentum is. It's cool to watch the little lightbulbs flick on over their heads - some higher wattage than others, but they are there nonetheless.
  3. Races: Build two of them and have teams race using only propulsion methods from within or on the craft; NO outside forces. This leads to all sorts of inventive, yet semi-successful, engineering ideas. Kids have, in the past,
    1. used a CO2 fire extinguisher for propulsion, thus demonstrating Uncle Newt's 3rd Law.
    2. used a huge electric fan like an everglade skimmer boat. Works, but won't break any land speed records.
    3. used an hand-held drill with a sanding attachment pushed against the floor like a running wheel behind the craft. This works quite well, BUT, be careful. The high RPM's of the wheel does create a large amount of frictional cutting into wooden gym flors, carpeted hallways, and little fingers that get in the way...

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