Balancing Nails Experiment
- Firmly place one nail into the center of the board. Place the block flat on a desk or table and try balancing the remaining 11 nails on the head of the standing nail. Be creative! But don’t cheat by using things like magnets, glue, gum, spit, etc.
NOTE: To win this challenge, all 11 nails must balance exclusively on the single standing nail. 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. Impossible? We’ll show you how it’s done! The key is to arrange the nails so all of their mass is evenly distributed and they can be supported on one point. Ready?
- Lay any nail flat on the table with the head on either the right or left side. This is nail #1. Hook the head of nail #2 over #1 so that it is next to the head of #1. #2 is perpendicular to #1. Nail #3 also hooks over #1 but points in the opposite direction as #2 and is also perpendicular to #1. The heads of #2 and #3 should be separated by about the width of nail #1. Continue laying the nails in alternating directions, leaving one nail aside. When you have done this, you should have five nails on one side and four on the other.
- Nail #11 is laid on top of all the heads but points in the opposite direction as #1. Nail #11 rests nicely between the heads of the nails you just hooked to #1.
- Use two hands and carefully lift all the nails by holding the ends of #1 and #11 together. Now, use the center of the group and balance all 11 nails on top of the lone standing nail. It might take you a couple of tries, but trust us… you’ll get it!
- 12 Nails
- Adult supervision
How Does It Work?
The trick to balancing the nails is in locating their balance point. Gravity pulls an object toward the Earth as if all of the object’s weight were concentrated at one point on the object. It’s called the center of gravity or the center of mass (if gravity is uniform). As you’d expect, an object falls over when its center of gravity is not supported. For balanced, symmetrical objects like a baseball or a meter stick, the center of gravity is exactly at the center of the object – – inside it. For objects that are not symmetrical, like a baseball bat or a hammer or your glom of nails, the center of gravity is closer to the heavier end and can sometimes even be outside the object. In this trick the stability of the nails depends on the center of gravity of the glom being right at or directly below (that is, outside of) the point where they touch the lone standing nail. Add more nails to the left side or the right side and not the other side, you’ll move the center of gravity in that direction or away from its support. The mass becomes unstable and falls off the lone nail with a crash!
Take it Further!
Now that you have mastered the Balancing Nails puzzle, try different ways to experiment with it. Are there other objects that you can use instead of the nails that you can still balance? How about larger or smaller nails? Just remember that it’s all about the center of balance and you will never go wrong!
Scientific puzzles can often 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 one idea doesn’t work, you might think of another one at the same time. The key is not to get frustrated and then give up. Keep trying! You might have to sleep on an idea and come back to it the next day. Keep notes or even photos of what you try and describe the outcome you had. You may want to share your ideas with someone else to see if they have a different approach to solving the problem. Draw a simple picture of what you’re trying to do to organize your thoughts. This is a problem solving process and it’s exactly like the scientific method: ask a question, run some tests, ask another question, run some more tests, and eventually you’ll come to a conclusion. If your experiments or “solutions” don’t work the first time, that’s okay. The key is that a scientist doesn’t give up if the first attempt flops. Some of the greatest scientific discoveries have been made because of mistakes!
Science Fair Connection
Preforming the Balancing Nails experiment is pretty cool, but it isn’t a science fair project. You can create a science fair project by identifying a variable, or something that changes, in this experiment. Let’s take a look at some of the variable options that might work:
- Try testing different size of nails. Which nails work the best?
That’s just one idea, but you aren’t limited to that! Try coming up with different ideas of variables and give them a try. Remember, you can only change one thing at a time. If you are testing different objects, make sure that the other factors are remaining the same!