古代の武器 ボーラ／Bolas: An Ancient Weapon *Audio in EN / DE / FR / PT / ES

DENJIRO: Here's today's topic: bolas! It was a tool used in the past for capturing animals. Let's try it out. You throw it by holding one of the balls and spinning the other two. When the bola was released, the three weights spread out and then wrapped around the pole. The key here is that the three weights spread out, but why does that happen? Let me explain using dry ice. I have three pieces of dry ice connected by a string. Just like when a bola is thrown, I'll spin one piece of dry ice so that the other two spin around it. Now, let me release it. At first, when I was spinning this around, the other two pieces of dry ice were close to each other, but when they were released, the pieces spread out. When it was first released, the center of rotation was at the two weights, and centrifugal force caused them to separate. As the weights drifted apart from each other, the center of rotation moved toward the knot in the middle, and therefore the bola moved with the knot at the center. Then, why does the bola get entangled with the pole? Let's try another experiment. I have a string with a smartphone attached to one side and a weight attached to the other. I'm holding the weight, which is lighter than the smartphone. The string is hanging on a rod. The smartphone is just hanging from the string. Also, I have a bucket full of water under the smartphone. If I let go of the string now, you may think that the smartphone will fall into the water. Let's see what actually happens. The string wrapped around the rod! When I let go of the weight, the string became shorter and shorter as the weight spun. The shorter the string, the faster it spins. This causes the centrifugal force to increase, causing the string to wrap tightly around the rod. This is the same principle as a bola wrapping around an object. I hope energy will bring you all happiness. Our magic word is "Happy Energy!"