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DENJIRO: There is a nail hammered into this wooden board. Even if you try to pull it out with a pair of pliers using all your might... the nail is too deep in the board to pull it out. But if you use this nail puller... As you can see, you can easily pull it out without using much force. This makes use of something we all know: the principle of the lever.
NARRATOR: If the distance between the fulcrum and the nail is short, and the distance between the fulcrum and the grip is long, there is more force exerted on the nail. Therefore, you can easily pull out the nail by moving the nail puller without much force.
DENJIRO: Now, let’s experiment with the power of the lever using this large contraption. The place at where the rod is hung is the fulcrum. We have a staff member sitting on a swing that is suspended from the end of the pole. And if we pull on the other end of the pole...
GIRL: The man was lifted!
DENJIRO: We were able to easily lift the staff member using the principle of the lever.
NARRATOR: The ratio between the distance from the fulcrum to the rope on the right and the distance from the fulcrum to the swing is 4:1. That means the man on the swing can be lifted with a force that is one fourth of his weight.
DENJIRO: Using this principle, we can easily measure the staff member’s weight.
NARRATOR: A basket is now suspended at the place that was pulled on. The pole is even when there is nothing on either end. Now, just like before, the staff member sits on the swing. Two-liter bottles of water are placed into the basket one by one. Eight bottles have been placed in the basket.
GIRL: He’s been lifted up!
NARRATOR: The staff member has been lifted up, and the pole is now balanced.
DENJIRO: 8 two-liter bottles weights 16 kg. The ratio between the distance from the fulcrum to the rope on the right and the distance from the fulcrum to the swing is 4:1. If we multiply 16 times 4, we get 64 kg. That means the staff member weighs about 64 kg.
I hope energy will bring you all happiness. Our magic word is "Happy Energy!”