Balancing Nails - Science Magic
Find the center of gravity as twelve nails find precarious stability on the head of just one nail.
The object of the challenge is to balance all of the nails on the head of a single nail. All of the nails have to be balanced at the same time and cannot touch anything but the top of the nail that is stuck in the base. If you're really ambitious, you can try your luck at our large-scale version using landscape nails and a friend as the base. Enough of this idle chatter... get balancing!
- A block of wood
12 identical nails with heads
(use 10 penny size or larger)
- Safety glasses
- Start by hammering one of the nails into the center of the block of wood. The nail does not have to be perfectly centered, but the closer it is to center, the better! NOTE: It can be a good idea to measure and pre-drill the hole to avoid splitting the wooden block.
Place the wood block flat on a desk or table and try to balance the remaining 11 nails on the head of the standing nail.
To win this challenge, none of the eleven nails may touch the wood block, the desk or table, or anything else that might help hold them up. No additional equipment other than the wood block and the nails may be used. It may seem impossible… but let us show you the trick! The trick is arranging the nails so that all of their mass is distributed evenly.
- Lay one nail flat on the table.
- Arrange the first of the remaining nails so that the nail head is propped up by the nail laying flat on the table.
- The next nail should lay in the opposite direction. The two nail heads should only be separated by the width of the nail that is laying flat on the table.
- Continue laying the nails in alternating directions until you achieve the pattern shown at right.
- The final nail should lay in the opposite direction as the nail laying flat on the table. This final nail will rest nicely between the heads of the propped nails. Again, refer to the picture at right for how this should look.
- Carefully lift the nails by the nails on the top and bottom of the pile.
- Now find the center of gravity and balance the nails on the top of the standing nail. It might take you a couple of tries, but trust us… you'll get it!
How does it work?
The trick to balancing the nails has to do with their "center of gravity" or balancing point. Gravity pulls an object down as if all of its weight were concentrated at one point called the "center of gravity." Objects fall over when their center of gravity is not supported. For symmetrical objects like a ball or a meter stick, the center of gravity is exactly in the middle of the object. For objects that are not symmetrical, like a baseball bat, the center of gravity is closer to the heavier end. The stability of the nails depends on their center of gravity being right at or directly below the point where they rest on the bottom nail. Add too many nails to the left or right and they become unstable and fall off.
Scientific puzzles can be trickier than they look. The best way to solve a puzzle is to think of an idea and then try it out. Even if it doesn't work, you might think of another idea at the same time. The key is not to get frustrated and give up. Keep trying. You might even have to sleep on an idea and come back to it the next day. You may want to share your ideas with someone else to see if they have a different approach to solving the problem. This problem solving process is exactly like the scientific method - ask a question, run some tests, ask another question, run some more tests, and eventually come to some conclusions. If your experiment or "solution" doesn't work, that's okay. Some of the greatest scientific discoveries have been made by mistake!
Balancing Nails Experiment
December 11th, 2012
Click the thumbnail below to see the video.
RE: Balancing Nails
Steve Englewood, Colorado - January 21, 2010
John - You're so kind to write. Thanks for the kind works… and I hope you try the nail demonstration. We've shared the detailed instructions online at http://www.stevespanglerscience.com/experiment/00000083 I love the version that you mentioned using the forks and toothpick. I also have this one online - you might want to see if your version is different. You're right… it's a great demonstration of the center of gravity and torque. http://www.stevespanglerscience.com/content/experiment/00000117 Thanks again for watching.
John H. Denver, Colorado - January 21, 2010
I love to watch your segment each Monday on 4:00 at 9 News. I've missed a few, but not many. I wish I had 100%. I was especially interested in your presentation yesterday, 1/18/10 wherein you were able to balance the nails on the head on one nail. I can't wait to try it when my garage, which contains my 16 penny collection, warm up enough for a trial run. You reminded me of a fun visual that I use to thoroughly amaze friends and foe alike. Are you familiar with a balancing demonstration wherein one uses a fork, spoon, toothpick, water glass and match? It's fun, I'm told it's a demonstration of torque. If you are interested, I'll try to explain it in writing.