Balancing Buddies

Using art and physics, this simple craft plays with an object’s center of gravity to make a fun little toy that surprises and delights little engineers!

Throw a ball in the air and gravity pulls it right back down, but not everything falls straight down when gravity is acting on it. Most objects are not simple spherical shapes like balls, so gravity acts on these more complex shapes in more complex ways. All objects behave as though their mass (the matter from which they are made) is concentrated at a point called their center of gravity. A simple spherical object, like a ball, has its center of gravity located at its center. In a more complex object can be located somewhere else. In your body, the center of gravity is typically slightly higher than your waist, because more weight is in the top half of your body than in the bottom half.

To create this toy that plays with gravity and equilibrium, we will move a cork’s center of gravity away from its center, causing our “Balancing Buddy” to rock and sway, but remain standing upright. We originally saw a craft similar to this in a Parents magazine, but after a bit of tweaking and adding some science-based research to the project, not to mention much doodling and decorating, we discovered that playing with gravity is quite a bit of fun!

Supplies:

(1) wine cork
(2) 12-inch bamboo skewers
(1) toothpick
Air-dry modeling clay or Playdoh
Colorful construction paper
Googly eyes
Pompoms of various colors and sizes
Colorful plastic beads (light weight, but large enough to thread on skewers)
Markers
Scissors
Glue Gun

Directions for Assembly:

Decorate the cork using markers. (We chose to make a silly face. If adding google eyes, pompoms or other 3D features, wait until further assembled – step #9 – so features can completely dry/set undisturbed. If doing this craft with very little ones, it’s best to let them decorate and manhandle the cork now, rather than after skewers are inserted to avoid frustration.)
Decorate skewers as desired with markers.
On a firm work surface, place cork so it is standing on end, with “face” oriented upside-down so Buddy is standing on his “head.” Press the pointed end of a skewer into one side of the cork about 1/3 of the distance from the bottom (his “feet”), at a 45-degree angle. Repeat on the opposite side. (See drawing above by my 8-yr-old assistant for clarification.)
Press the toothpick into the center of the cork.
Feed 1-2 beads onto skewers as desired. Be sure to keep equal number of beads.
Roll two equal balls of air-dry clay or playdoh, about the size of a large grape. Press one ball onto the end of each skewer, careful to not puncture all the way through the clay ball. (This will hold any beads in place as well.)
Using paper and/or pompoms, create a cone hat and/or other accessories for your Buddy. Be sure to keep to the top of the cork and evenly balanced or symmetrical.
Use hot glue gun to secure in place. (We glued a large pompom on the top of the cork; then glued a paper cone “hat” over the hidden pompom to provide a stable and generous gluing surface. We then added another small pompom to the top of the hat. See drawing above by my 8-yr-old assistant for clarification.)
Complete face by adding google eyes, pompom nose, etc.

How to Balance:

Place the tip of the toothpick on your finger or on the palm of your hand to see if Buddy balances. If it tips over or leans to one side, adjust the angles of the skewers until it stands upright. Still unbalanced? Make sure the two clay balls are the same size, larger than a grape, smaller than a ping-pong ball.

How does it work?

Every object has a center of gravity. This is the point where its mass is evenly distributed and the object is balanced and stable. While the cork appears to be the solid, stable center of our little “Buddy,” the clay balls are actually heavier than the cork and bring the center of gravity all the way down to the bottom tip of the toothpick. By shifting the cork’s center of gravity downward and away from the center of the cork, our Buddy must balance, or stand on the tiny wooden tip. To keep Buddy upright, the weight of the two clay balls must also be balanced. This means they must be the same size and weight, as well as symmetrically placed on the skewers.