DENJIRO: There’s a technology that has been in use since Before the Common Era to lift heavy objects. It’s the pulley. So how are you able to lift heavy objects with it? Let’s pull someone up with a pulley to explain. There’s a pulley attached up high. There’s a pulley below, which has a rod that has a swing hanging from it. A rope attached to the top is going through the two pulleys multiples times, and the other end is hanging down by my side. You can see that the bottom pulley is essentially hanging by four ropes. Now, let’s use this contraption to lift someone up. My assistant is going to sit on the swing. He weighs about 60 kg. Let me pull the rope to lift him up.
GIRL: You were able to easily lift him up!
DENJIRO: Now, let’s have two people sit on the swing. The total weight is about 140 kg. It’s pretty heavy.
GIRL: Wow!
DENJIRO: I was able to lift them up. It’s not that I’m particularly strong. So why was I able to lift them up? The weight of the two people were being supported by four ropes because of the pulleys. This results in the force needed to lift them up becoming one fourth their weight. The pulley that’s not fixed and has the swing hanging from it is called a “moveable pulley.” If you use a moveable pulley, you can lift heavy objects with little force.
You can easily lift yourself up with a moveable pulley too. I’m going to give him the rope that I was pulling on earlier. He’s going to pull on the rope himself. In this case, since he’s holding the rope himself, his body weight is being supported by five ropes. As a result, he can lift himself up with a force of just one fifth his weight of 60 kg, or 12 kg.
I hope energy will bring you all happiness. Our magic word is "Happy Energy!”
11 сен 2024
