hey guys! hey there, squid! how’s it going? tgs: mmmph. iâ€™m kinda cranky right now. jessi: oh no. no one wants that. whatâ€™sbothering you? tgs: cruise ships. jessi: cruise ships? tgs: yeah, cruise ships. you know, those giantboats that you people sail around in. thereâ€™s been one floating above me all day, and icanâ€™t get any sleep! i mean, itâ€™s huge! and noisy! itâ€™s likea floating city! so, instead of sleeping, iâ€™ve just beenbobbing awake, staring at it, and wondering.
how does a giant ship like that float on thewater? i mean, heavy things sink in water, right?like when someone up there tosses a rock into the ocean — which happens, you know — itsinks. so why does that heavy ship get to float? jessi: the reason a big, heavy ship like thatcan float has to do with its shape. whether an object sinks or floats to beginwith has a lot to do with something called displacement. displacement is when an object displaces,or pushes aside, water. so, like, when you drop an ice cube into an already-full glassof water, some water spills out.
tgs: thatâ€™s displacement? jessi: thatâ€™s right — the amount of waterthat spills out is actually equal to the amount of space the ice cube takes up! or think about when you take a bath. tgs: hold up. wait. whatâ€™s a bath? jessi: well, up here, we like to clean ourselvesup by soaking in a tub full of nice warm, soapy water. tgs: that sounds gross! do that mean thathumans just walk around all day getting dirty? if you spent all of your time in the waterlike me, youâ€™d never get dirty in the first
place. jessi: well, not everyoneâ€™s the same, right?i know some of the people watching here know what a bath is. tgs: mmmrph, okay. jessi: so, say you fill the bathtub up — allthe way to the top. and then you climb in. now thereâ€™s water on the floor. lots ofwater. the amount of water equal to the amount of space that you took up! now, one of the secrets to an object beingable to float, is that it has to displace enough water so that the water it pushes asideweighs as much as it does.
alright, so, say youâ€™re in the tub and youwant to do an experiment. you can bring in a small bowl, and some rocks from your rockcollection. if you put the bowl in the water, itâ€™llfloat. because the bottom of the bowl is displacing some water. and the amount of water that itâ€™spushing aside weighs the same as the bowl. now, drop a little rock in there. add another, and another. the bowl is getting heavier, so itâ€™s sinkinga little bit each time. but even though the bowl is heavier, itâ€™salso displacing more water — so the amount of water that itâ€™s pushing aside still weighsthe same as the bowl.
tgs: so what does that mean for the cruiseship? why doesn’t it sink? jessi: well, ships are designed to displaceas much water as possible. theyâ€™re realllly wide, and their bottomstend stretch down really far, so they push aside a lot of water. plus, a ship has lots of empty space insideit — a lot of it is hollow — which helps to keep it light, compared to the huge amountof water that itâ€™s displacing. and voila… it floats. tgs: ok, ok. so that giant, noisy party overmy head right now is displacing enough water that it can float.
well, you people may be noisy, but the factthat you figured out how to build giant metal things that floatâ€¦ thatâ€™s pretty clever,iâ€™ll give you that. jessi: yeah, and i don’t know about you, butsome of my favorite things tend to clever and noisy. thanks for joining squid and me,learning about displacement. see you next time! tgs: bon voyage!