Balancing eating utensils on the rim of a glass is a trick that requires moving gravity a little bit.
A balanced diet is always a good idea to help you stay healthy. Here’s an activity that’ll be a hit at home or at your favorite sit-down restaurant. (Our guess is you’ll either get a free dessert or you’ll be asked to leave.) Find a way to balance a fork and a spoon on the edge of a glass using only a toothpick. Yes, it’s a balancing act with a most interesting, gravity-changing solution.
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- A fork and a spoon (or two forks)
- Round toothpick
- Heavy drinking glass (or half-fill a lighter one with water)
- Adult supervision
Start by pushing the two center tines on the fork upward a little. (This is probably not the best thing to do with heavy or expensive utensils; cheaper is probably better.)
Push the fork and spoon together so the bowl of the spoon is under the two center tines, but over the outer two tines of the fork. It’s useful if the fork and the spoon weigh about the same.
This step may take some practice. Balance the utensils on a fingertip to find the middle point. This is where the toothpick should be inserted between the utensils. Work the toothpick into the tines of the fork.
Carefully set the toothpick on the rim of the glass. Slowly slide it in or out across the rim until you’ve found the best balance point. Both handles will be curving downward below the rim of the glass and the toothpick will be almost horizontal.
Once you’ve mastered the balance, you’re ready to show off a little. Strike a match (that’s a job for an adult) and burn the end of the toothpick hanging over the inside of the glass. To everyone’s amazement, the toothpick will burn down to the very edge of the glass but the utensils will not fall.
When that flame stops, light the end on the outside of the glass and watch it burn. It stops at the utensils but they remain balanced. What a show!
How Does It Work
The center of gravity of an object refers to the central location that gravity acts on the object. In this activity, the center of gravity is straight down from the spot where the toothpick sits on the rim of the glass (called the pivot point). If you look closely at your balancing utensils, you’ll notice that the handles are curved well below the toothpick. This actually moves the center of gravity directly below the point where the toothpick touches the rim.
If the glass has slanted sides, the center of gravity— where the utensils balance front and back, left and right, up and down— is actually located in mid-air next to the glass. A tightrope or high wire walker often uses a long stick for balancing in the same way as the forks are used in this experiment.
If you burned the ends of the toothpick, you may have been surprised that the utensils remained balanced. Why didn’t the flame keep burning and cause a collapse? Fire requires three things: heat, fuel, and oxygen. Take away one of these and the fire goes out. The fuel and oxygen were there but you took away the heat. The glass and the metal rob the flame of its heat and it dies.
The real secret to this activity is to not give up or get frustrated if the utensils fall. Just rebuild and try again. Once you’ve mastered the balancing act, you’ll be the hit of any dinner party.
Take It Further
The Cork-Fork Mystery
Some balancing-fork enthusiasts find this variation more challenging. Give it a try.
- Position a toothpick in the very center of one end of a cork and push it straight into the cork. You don’t have to push it too far.
- Carefully push one fork into the side of the cork closer to the end with the toothpick in it. The handle should curve downward toward the toothpick.
- Push the second fork into the cork directly opposite the first fork. The cork-fork-toothpick device should be as symmetrical as possible.
- Balance the end of the toothpick on the tip of a index finger, on the top of a bottle, or on the corner of a table. Don’t be surprised if your “science art” balances in an unusual position. Remember, you’ve moved the center of gravity to just below the pivot point.
- Actually, the toothpick does not have to be positioned in an end of the cork. Push the toothpick into the side of the cork at an angle near the bottom to discover a new center of gravity. Of course, you may have to adjust the location of the forks to achieve complete balance.