Placeholder Image

字幕表 動画を再生する

  • Cogito, ergo swim?

  • Today on Michael's Toys, we're going to be building a cartesian diver named after

  • Rene Descartes.

  • It's a very cool thing that you can build at home yourself.

  • You will need enough water to fill a squeezable plastic bottle that has a nice tight-fitting

  • lid, four sugar cubes, four paper clips, at least a couple toothpicks, a teaspoon of cinnamon,

  • two different colors of vinyl electrical tape, some transparent tape, an assortment of ketchup

  • packets, a small metal bowl, and a pencil that you have kept

  • in a dish of salt at least overnight.

  • A full list of all of these materials can be found down in the description below.

  • Step one is to uncap our plastic bottle.

  • This will contain the ocean that our cartesian diver explores.

  • Our diver will be a ketchup packet.

  • Now you could use a packet of any other kind of sauce, mayonnaise perhaps, mustard, but

  • I find that ketchup works the best.

  • Ketchup, it's perfect.

  • So what we're gonna do is squeeze up the little packet of ketchup and insert it into

  • the bottle.

  • Plop!

  • Perfect.

  • Now that our diver is in there let's give it an ocean.

  • I will put the bottle in this little bowl just in case I spill which I'm sure I will.

  • Let's see if I have enough water.

  • Perfect.

  • Alright.

  • Now make sure the cap goes on very very tightly.

  • Perfect.

  • Okay.

  • Now here we go.

  • Let's dry this off and get ready to dive.

  • So our ketchup packet is floating in the bottle.

  • Floating up towards the top.

  • But for how long?

  • Watch this.

  • Watch what happens when I squeeze the bottle.

  • Not so floaty now are you?

  • But if I stop squeezing, it floats back up to the top.

  • I can not only make it sink but I can make it stay right where I want it to stay just

  • by applying the right amount of pressure to the bottle.

  • I can send it to the bottom with a strong squeeze

  • and free it to the top by simply loosening my grip.

  • It's enough to make anyone go Oh boy!...ancy.

  • When an object is immersed in a fluid whether it be a gas or a liquid, pressure is exerted

  • by that fluid on the object because the object is being bombarded by the molecules that makeup

  • that fluid.

  • Now getting bombarded by a single molecule isn't much but try getting bombarded by

  • trillions.

  • That could cause some pretty large pressure.

  • But here's the thing, the actual magnitude of the force that comes from being bombarded

  • by a fluid's molecule increases the deeper down that molecules is because of the weight

  • of all the fluid above it.

  • Which means when you're submerged in air or water the pressure at the bottom of you

  • is greater than the pressure from above so any collisions that occur top down like this

  • pushing you down are weaker in total than all the ones pushing you up.

  • Now the difference is a net force up and that force is called a buoyant force.

  • But how strong is the buoyant force on an object in a fluid?

  • Well take a look at this ketchup packet. Alright it is surrounded by water.

  • But if it wasn't in this bottle what would be in its place?

  • Well just water. Water would be filling that volume.

  • The water of volume the exact same size and shape as that ketchup packet would be there and what would that volume of water be doing?

  • Would it be sinking or floating? No.

  • So there ya go. The weight of that parcel of water equal in volume to this packet

  • would be equal and opposite the buoyant force pushing in the other direction.

  • So it would stay where it is and not sink or float.

  • This observation is known as Archimedes' principle.

  • The buoyant force on an object is equal in weight to the volume of water it displaces by being in that fluid.

  • In the case of this ketchup packet the packet has a smaller weight

  • than an equal volume of water so the buoyant force wins out

  • and the packet floats.

  • But not for long because inside almost all sauce packets

  • there's a little bit of air and air is much easier to compress

  • than sauce or water so when I squeeze the bottle

  • The water pressure inside the bottle goes up and all the air in that packet compresses. It gets smaller.

  • Which means the volume of the packet gets smaller.

  • But its weight stays the same so all of a sudden we're talking about a smaller volume

  • with the same weight. That's more dense.

  • Denser things sink.

  • When I release my squeeze the buoyant force becomes once again stronger than the weight force

  • because the volume of the packet increases.

  • Because the air that is right now compressed

  • expands back. The ketchup packet takes up more space.

  • Enough space that an equal volume of water

  • would weigh more.

  • Therefore the buoyant force moves it up.

  • So go ahead and try to build one of these at home and try out different kinds of sauces.

  • I have found that packets of ketchup work out the best.

  • I find that soy sauce packets, I've got one right here

  • They just sink right away. They are too dense.

  • Hot sauce packets from Taco Bell have the opposite problem

  • They float too well. Put one in, it'll

  • float and no matter how hard I squeeze I can't get it to fall. Maybe you're strong enough.

  • Try it out. It's called an experiment.

  • Thank you science. I find that not all ketchup brands

  • work equally well though. I have

  • some oh yeah so these Heinz packets, they also float too well.

  • If your packet sinks right away

  • it might just be on the edge and if you add some salt to your water

  • you may be able to get that packet to float because adding salt increases the buoyant force of the fluid in your bottle.

  • But I gotta tell you I've made dozens of these in my life and I always find that ketchup is the safest bet.

  • Watch this.

  • Are you guys watching?

  • wait watch...hold on watch this.

  • And as always, thanks for watching.

Cogito, ergo swim?

字幕と単語

ワンタップで英和辞典検索 単語をクリックすると、意味が表示されます

B2 中上級

直交ダイバーの作り方 (How To Make A Cartesian Diver)

  • 2 0
    林宜悉 に公開 2021 年 01 月 14 日
動画の中の単語