Thanks to a suggestion from Meg at Bare Baby Feet, this week’s Unplugged Project theme is balance. We felt “sciency” this week, so my oldest daughter and I scoured our favorite science book but found nothing that sounded fun to her.
I did a few Google searches and happened across this amazing-seeming experiment. I tried it and then showed it to my children who were very impressed. As you will see, I tried to make it even more fun for kids by modifying it to make a balance toy: a flying bird. Read on for more!
This experiment (which I understand is often shown as a magic trick), involves two identical sharp forks, a real cork (a real one is a bit softer and easier to use than a plastic one), a toothpick, and a glass. Push the forks into the sides of the cork.
They should be in the middle of the cork, directly opposite each other. The cork will not be in alignment with the forks. Try to have the forks at a 90 degree angle to each other, like this:
Push a toothpick into the end of the cork, on the side between the forks (be careful, the toothpick breaks easily, so be gentle). You will have something like this:
Experiment by balancing the toothpick on your finger. It seems impossible, but once you find the right spot, the forks will just balance. You can mark that spot on the toothpick with a marker, or just remember about where it was.
Place the balance point of the toothpick on the edge of a glass. The forks should remain suspended on the side of the glass. Pretty amazing!
Now, for the grand and very dramatic finale! Take a match and light the end of the toothpick on fire (yes, I really did say to set fire to the toothpick – YOU, not your kids of course :-) ). The flame will move up the toothpick, burning it into nothingness. The fire will stop when it reaches the rim of the glass.
Does the cork fall down? NO! It stays put, hanging by practically nothing on the rim of the glass. You can even lift it off and place it back on, barely touching the rim, and the whole thing will balance.
Here’s a video I made of the toothpick burning (I have never put a homemade video on my blog before so I really hope it works). Watch closely and you’ll see that my son tried to knock the whole thing off the glass at the end of the video but it just bobbed up and down and returned to its original position. Very stable!
How does this seemingly magical “trick” work? Warning: science stuff coming up – feel free to skip to the next section if this is all “blah blah blah” to you.
The secret to understanding this experiment involves a study of center of gravity and pivot point. The center of gravity is “the average location of the weight of the object.” Imagine balancing a see-saw.
But the center of gravity does not necessarily have to be on the object itself. Here it is actually in the open space between the forks. This means that, unlike a see-saw, the object is not balancing on its center of gravity (“CG”). Instead it is balanced on a separate pivot point (the toothpick on the edge of the glass) away from the center of gravity.
We had to arrange the forks so that their mass was a bit lower than the center line of the cork in order to insure that the CG remained lower than the pivot point. Since the CG is lower, if the fork assembly is displaced, the CG will be raised and gravity will pull it back to equilibrium. You can see this in my video. All balance toys have a CG that is below their pivot point. (NOTE: I am NOT a scientist! Any physicists out there may disagree with my terminology, etc., but I am trying to make this as simple an explanation as possible.)
THE FLYING BIRD:
Not wanting to use my good forks as permanent bird wings, I had to think of something else. A matching pair of thrift store forks would have been ideal, but the thrift stores were all closed today. I ended up using a set of small screwdrivers that came from the bargain bin at the local hardware store, and that turned out to be not what my husband expected. There were four screw drivers, so by using two corks, my daughter and I were each able to make a bird.
We stuck them into the sides of the cork at the appropriate angles (see above). They were actually easier to get in there than the forks were.
TIP: Test “fly” your configuration on a glass before proceeding further. Adjust the screwdrivers (or forks) now if necessary to get it right. I didn’t check mine before-hand and had to fiddle later after the feathers were on.
To create a good surface for sticking on feathers, I cut construction paper into a symmetrical wing shape. By folding the paper and cutting double thickness (while keeping a portion of the fold intact) this was easy:
We then covered each screwdriver with a paper wing and stapled it so that the screwdriver was hidden inside. Staple as close to the screwdriver as you can so the wings stay on. It doesn’t matter if the staples are in the middle of the paper because you are going to completely cover the paper with feathers.
Paint your cork if you want to.
Next, glue on feathers. We had “natural-looking” feathers and “fake-looking” feathers, both from Walmart a long time ago. I opted for a colorful, fake bird. My daughter chose to be more natural. Elmer’s white glue didn’t work so well, so I broke out the hot glue gun and we began sticking on feathers.
I found an old jar to be a useful stand for our sticky birds while they dried, as well as for painting the underside of the cork.
After things have dried a bit, you’ll need eyes (googly or beads) and a beak of some sort. We cut the tips off some new crayons with scissors to make our beaks and they made perfect beaks! Glue them on with the glue gun.
If you haven’t already, carefully stick a toothpick in the back end of the bird.
Once everything is well dry, you can “fly” your birds on the edge of a glass. If properly balanced, they’ll bob up and down when touched, but won’t fall off. PLEASE don’t try the flame trick since you don’t want to risk setting all the glue and feathers on fire!
If you did a balance project this week, then please link to your project post in Mr. Linky below. I really prefer links to project posts rather than blogs in general, so that readers will always be able to find your project no matter how far down it is buried in your blog. If you did not do a balance project, please do not link. Read more about how to participate here. We’d love to have you join us!
The theme for next week’s Unplugged Project will be: