Balloon Propeller (Newton's Third Law)
How we did it:
- straw (bendable)
"D'you guys remember this one?" I asked.
"No," answered my daughter Trev. "Is it a gravity experiment?"
"Nope! Newton's Third... do you remember which law that is?" And so it began....
First, Trev stretched the balloon by hand and blew it up a bit to stretch it out further.
The next step is to tape the balloon to the end of the straw (the opposite end of the bendy part). There needs to be a good seal, so I did that part myself.
"Where does it balance? Can you find the balance point?" I asked.
Trev put the straw on her finger and figured out at what point the straw balanced. Excellent. When the balance point of the straw was found, she poked the pin all the way through the straw (both sides)...
and poked the pin into the top of the pencil's eraser.
She spun the straw around the top of the pencil several times to stretch the pinhole a bit (you want to get the pinhole nice and loose so that the straw can spin easily). Then she blew up the balloon.
Once the balloon was filled with air, Trev held on to the pencil and watched the balloon fly! There was definitely lots to talk about: "Remember Newton's third, now?" "What did you do to the balloon?" "Why does the air come out? And why does it spin?"
Air, energy, actions, and reactions. Excellent. Simple and effective!