okay, gang, let's begin. we talked about archimedes' principle. true or false, archimedes' principle says,

that the amount of buoyant force that's gonna act on any immersed object would be numerically equal to the weight of the object? false. false? let me try another one. very good. archimedes' principle says, "the amount of buoyant force "that will act on an immersed object "is numerically equal to the weight of the fluid displaced by that object." it's true. hey, huh, huh. there's a difference, right? yeah. is that true? let me ask you a question like this. this piece of iron, very, very dense. i'm gonna put the iron in the water. yacko, it sinks. hoom, really sinks. some people say, "well, that's because there's no buoyant force acting on it," and you say-- there is. there is or isn't? there is. answer begins with i. is. is. okay. you like that hint? okay. turns out there is. how about this piece of wood? this piece of wood have the same size,

has the same volume. i'm gonna put that in. he was, like, "oh, there's a buoyant force acting on the wood." yeah. it's true. some people would say, "the fact that the iron sinks "and the wood floats is evidence that there is more buoyant force on the wood." to that, you would agree or you would disagree? knowing they're the same volume. see what your neighbor says. which has the greater buoyant force, the sunk iron or the floating wood? and realize they're both the same size, same volume. how many say there was a buoyant force on each, and son of a gun, the buoyant force was greater on the submerged iron? some people say that, but some people don't.

now, let's use archimedes' principle to answer the question. archimedes' principle says, "the more water displaced, the more buoyant force." yeah or no? - yeah. - yes. yeah. so some displaced a lot of water, a lot of buoyant force? how about some displaced only a little bit of water? a little buoyant force. okay. this is both at the same volume, same size. when i put them in, one sinks. now, i wanna ask you a question, which has the greater buoyant force? and when i ask that question, i want you to use archimedes' principle to answer the question. let's suppose instead i said which one displaces the most water? the one that sinks all the way underneath or the one who only sinks a little bit? what would you say? the one that sinks all the way. this side of the class, what would you say? the one that sinks all the way? the one that sinks all the way happened to be iron. and the one that sinks all the way displaced the most water. so the one that sinks all the way has the greater buoyant force. do we all see that? yup.

so one is floating and one sinking. there is two things to consider, gang. two things to consider. here's my object in the water. here's the buoyant force. but there's something else to consider. here's the weight. in fact, there's a lot more than that. it turns out the weight would be over five times as heavy as the buoyant force for iron. irons are very, very compact. iron is very dense. nevertheless, there's the buoyant force. if i took this iron and held it like this, which has got the greater buoyant force? the iron like this? or like this? or like this? exactly. yeah. yeah, yeah. see, so the buoyant force has to do with the weight of water displaced. and it's gonna sink-- displace a lot more water like that, than, say, if it's up here floating. i don't have to tell you if this is wood or iron. all i have to tell you is, "hey, how much water is displaced?" you got the answer to how much buoyant force.

so the thing that has the greatest buoyant force is the thing that could displace the most water. you kinda see that? okay. here's a piece of clay. we talked about this last time. here's a hunk of clay. take the clay, it sinks. any buoyant force acting on the clay? yeah. there's a buoyant force acting on the clay. how much compared to the weight? less. there must be less. the weight must win. that's why it's on the bottom. so the weight wins. what i'm gonna do is i'm gonna refashion the clay and make it into like a boat. now, when i put it in, it will displace more water before it sinks. and let's see if it displaces enough to-- the same clay floats. hc. how many say, "i don't know. i didn't be knowing clay floats."

but some clay floats, honey. [laughter] if it got the right shape. or is there more to it in that? is there more to it than that? when i made the clay wider, didn't it displace more water? guess how much water it has to displace to float. more than its weight-- as much as its own weight. because now, guess how the buoyant force compares to the weight. one guess, when you see the system in equilibrium not accelerating. take a guess. not even take a guess, take a good--take an estimate. what is it? and you know what it is, it's the same. and that's a complication for a lot of people because for floating objects, the buoyant force not only equals the weight of water displaced, it also equals the weight of the object doing the displacing. can you see why some people, boom, they can't handle it, they get mixed up. so it's only when you float that the buoyant force and the weight of the object are both the same. see?

if i make the buoyant force less by having it displace less water, then the buoyant force is not big enough to support the weight, and so the weight's the same, buoyant force is less and-- [makes sound] and it goes in the direction of the net force, yeah? kinda see that? make sense? lee, question. when you reshape it, though, you aren't changing the density of the clay by itself. so what makes it less dense overall? so that-- yeah. we haven't really talked about density yet, have we? but it turns out-- now, i don't change the density of the clay. but i do, nevertheless, when it's submerged like that, get a big air pocket. so as far as the water is concerned, there is something with less-- something of less density when you consider the space that the air pocket takes up. so counting this-- like a hollow piece of iron, of course, will float, see, because it's got the air inside. so the overall density is less. so i can say the overall effective density if you count from, you know, counting the air that's trapped in there.

not trapped in there but which just support it, kinda something like that. let's talk about density. make that a little clearer, i hope. here's an object. i'm not gonna tell you what the object is 'cause, you know, we don't care what the object is. but the object in there is taking up that much water. we say it's displacing that much water. hey, gang, if you weighed that much water, you got a value for it, okay? how would that compare to the buoyant force that acts on that unknown object? it begins with ss. - same, same. - same, same. okay. in fact, the weight of water displaced is gonna give me an upward buoyant force. now, let's suppose this object happens to be a baggie filled with water. then how heavy will it be?

and it turns out it'll be just as heavy as the buoyant force. so you know what it does? it doesn't sink. it doesn't float. it just remains at one with the water because it has the same mass, has the same volume of water, which is to say it has the same density. so if something has the same density as water, it's not gonna float, it's not gonna sink, it's gonna do neither. the density of water is one gram per cc. one gram per cc or 1 kilogram per liter or 62.4 pounds per cubic foot. that's the density of fresh water. i got a question for you. is there anyone in here that happens to know the numerical value of density for a freshwater fish? check your neighbor. any buoyant force in a fish, gang? yes. show me a fish with no buoyant force and i'll show you a fish in a vacuum, okay?

a fish is displacing fluid, usually water, if it's healthy, right? and so there's a buoyant force acting upward. any gravity pulling in that fish? yes. oh, yeah, and that's pulling down. guess how hard the gravity is compared to the buoyant force as such that the fish stays there. come on. - same. - same, same. so what's the density of the fish? water. the same as water. so if i tell you water has a density of 62.4 pounds per cubic foot, then you guys know what a fish density is in cubic feet. 62.4 pounds, okay? guess what your density is, more or less than 62.4 pounds per cubic foot. more or less? all the ladies in the class will be saying less. most of the dudes will be saying less. but some dudes say, "hey, honey, ain't talking to me "because i don't know why, "but i try and i try and i just can't float. "and my friends are telling me why and they're all saying that i'm too--" [laughs]

yeah, too dense. too dense. yeah. people that have no fat, no fat, very, very muscular, very compact are a little bit more dense than water. they sink in water, hear that? because let's look at this over here. this is the size of anything. if the weight is like that, then it weighs more than an equal volume of water and what can we say about its density? greater than an equal volume, greater than water-- that of water. what's this object with an-- forces which way? down. which way is it gonna go? - down. - down. it's gonna sink. so objects that are more dense than water will sink in water and we see why. because the buoyant force is not enough to keep up with the weight. let's suppose this object has a weight like this, very small compared to water. okay. any buoyant force? yeah. buoyant force is the same as before. remember, the buoyant force doesn't have to do with the weight of this at all. it has to do with the size of it, how much water it's taken up.

it has to do with the weight of water displaced and that depends on the size of the object displaced in the water. yeah? this object here now is--has a net force acting which way? begin with a u. up. end with a p. put it together. up. up, okay? guess which way it goes. up. it goes up until it-- floats. --floats. see? it'll finally go to the surface and get to a point here now. there's less buoyant force at the surface. is there less buoyant force at the surface? yes. you bet there is, okay? and now that weight and that buoyant force, both balance and it floats. so here we have the idea that the weight of the object itself equals the buoyant force and that's the principle of floatation. so if something is more dense than water, sinks in water, less dense, floats in water, same density-- [makes sound] --stay right there. i got a question for you. here's our fish. it's in a bowl. it's a pet fish. we like that fish.

we find out that when we feed that fish, the fish goes right to the food. if we put the food in the bottom, the fish goes down and gets it. food--put the fish-- the food in the top and the fish goes up. how does the fish go up and down? it takes its flippers and goes down like this and it go back up like this, right? let's suppose we take those flippers and cut them off. [laughter] it's for science. all right? all right. now it could take the tail on to it, right? all right. we cut the tail off. with the eyeballs. okay. now, oh let's suppose we-- that's a little cruel. let's suppose we just take the flippers and put scotch tape over them, okay, and put a couple of splints in the tail. okay. now, how can the fish go down if it wants to go down? how many say, "it can't do anything now, got no flippers"? how many say, "i think the fish still can go down"? here's a little hint.

if the fish is gonna go down, what does the fish have to do to its density, make it more or less? more. is there any way for the fish to change its density? yes. what can it do? breathes off the air. it can contract its--bladder. it can make its volume smaller. if it pulls in on its bladder, pulls in, it'll sink, okay? and so the-- let's suppose, all of a sudden, you put better food at the top. how's it gonna get to the top? it's gonna push out. push out, make the volume larger and it's gonna go right to the top. so a fish varies its density by varying its volume. submarines-- [makes sounds] --crash dive. they're down there, they come back. how does a submarine do that? by varying its volume? how does a submarine dive? how many say this? how many say, "hey, i learned enough physics that i know this. "that if a submarine on a surface dives, then i know that submarine must have somehow become more dense"?

how many say, "i don't see the connection"? [laughter] you're swimming and someone hands you a boulder. guess what you do, honey? okay? your overall density becomes more and what do you do? begin with an s. - sink. - you sink. and so the submarine becomes more dense not by changing its volume but by doing what? taking some water. there's one other choice, gang, for density. the equation guides our thinking, doesn't it? if it's not volume, what's the other choice? - weight. - weight. and so the submarine gets heavier. how does it get heavier? what does it do? it drinks water. it--water's heavy? if you have enough of it, yeah. and that water, drinks water, becomes heavy, it sinks. now it's down below, "hey, we wanna come to the top." what do they do? blow the water out. so the water is out, the submarine becomes lighter, less mass-- [makes sound] --right back up again. so a submarine does it by changing the weight and fish do it by changing the volume. got a project for you for saturday night.

saturday night, when you take your bath, okay, get everyone else out of the tub and bathe alone, okay? parents, "this is for science. i got the bathtub all to myself tonight, all right?" and here's what i want you to do in that bathtub. i want you to float back in the tub and i want you to take a great, big deep breath. and when you do that, see if you don't rise right off the tub. and when you're floating really high, then i want you to blow it all out and-- [makes sounds] --see if you don't crunch right back down on the bottom. what's going on there? have you guys tried that? yeah. you take a deep breath, you'll rise in the water. let it out and you'll go down. hc. submarine or a-- fish. --fish--like a fish. see? when you take a breath, don't your lungs get bigger? your volume gets larger, okay? so you don't have to sink as deep to displace the same amount of water. so you'll float higher.

so when you're higher, then you go-- [makes sounds] --like that, what happens? you cave in, you become more dense, and you sink. when you float, some people-- you're trying to teach your friends how to float and they're kind of freaking out. you tell them, "hey, take the deepest breath you can. now hold it." are they gonna float easier? yeah. yeah, they're gonna float easier because what's happening? their volume has increased. and so long as you keep as much air as you can, it's not the air, it's the idea that your lungs are out, you see? and if your lungs are out, you're less voluminous-- i mean, more voluminous, and you float higher. or how about you-- you're just barely can float and you let it all out? okay. i tried something yesterday in a swimming pool with a snorkel. i wanted to see how deep i could go with a snorkel. it turns out i could go about 30 inches, less than a meter, less than a meter deep. because when i get down a meter deep and i'm trying to breathe to that snorkel-- i put up a piece of plastic tube in the end of the snorkel. when i get down there-- [makes sounds]

--i could just barely breathe. hc. pressure of water. the pressure of the water, how it was pushing me in and contracting me and making the pressure in my lungs more. it turns out the pressure in your lungs will be the same as the water pressure outside. it'll squeeze in until-- and now i've got more pressure, 30 inches under the water, more air pressure on my lungs than up there. how many people say, "oh, just go like this and all the air will rush down to you"? it's not gonna go from low pressure to high pressure. when i was a kid, i used to think that if you're a deep sea diver-type, all you have to do is take a garden hose, put it between your teeth and swim down and you breathe it off the top. but i forgot about the idea that the water pressure squashes you in. --any air or you got in there, honey, go--go this way. could you imagine going down quite a few feet? you got your-- yeah, our lungs full of air. someone hands you an empty hose-- [makes sounds] what you got is gonna-- you get even--hey. you see that? water pressure depends on depth.

let's put all these ideas together and see if we can handle this one. it's life preserver time. and you look over there and you see two life preservers and they look both to be the same. nice orange color of the tags and everything. except one is filled with styrofoam and one is filled with lead pellets. someone says to you, "if you use the one with the lead pellets "and they are both the same size-- this was critical thinking time, gang. someone says to you, "if you put on the life vest filled with lead pellets, "it turns out you'll have more buoyant force on you than if you use the one with the styrofoam." and someone says, "you know what? "that guy is right. "there will more force-- buoyant force acting on you with the lead pellet one." yes or no?

- yes. - yes. that's like saying this, "hey, you wanna be held up?" "you wanna grab one of these? but i tell what? "if you grab the iron, "there'll be more buoyant force on it. than if you grab the wood." what's the answer? - yes. - yes. that's only one trouble. you're not interested in only the buoyant force. you're interested in something else. the net force. and gang, the weight is gonna overwhelm that greater buoyant force. it turns out the lead pellet-filled styrofoam life vest will give more buoyant force because, why? because it'll sink beneath the surface and displace all of its volume, whereas the styrofoam one will-- [makes sounds] --you'll be up like this. see? this part here not even displacing. so when you put on a life vest, all you're doing, gang, is you're decreasing your overall density. and when you increase your overall density, you do that by increasing two other things, one that you want to increase and the other you don't want to increase. and the one that you want to increase is what?

the volume. you want to increase the volume, so you get the puffiest thing you can. then that puffy thing is gonna have some weight, right? but not very much compared to the volume, and so even a small life preserver will float you nicely. all it does is it's add to your volume while only adding a little bit to the weight. so the friend that handed you the lead pellet one surely add even more to your volume, but humongously more to the weight, and that's why you drown. so strictly speaking, we see that there's a difference between the buoyant force that acts on something and the net force that acts on something. would you like another critical thinking-type question? how many say, "no, i'm tired. that's enough." let's try this one. some years ago, i had the good pleasure of swimming in the great salt lake in utah before they came in and embed it with fresh water. it used to be very, very salty and very, very dense. and you could float in the great salt lake. and honey, i just go up like this.

with regular water, you're down like this or something like that. with kerosene, you'd sink, okay? not too much density. okay. but in that great salt lake, you could float very, very high on the water. now, that's because there's more buoyant force on you if you float in the great salt lake. - no. - no. true? false? who knows? check the neighbor. okay, gang, what would be the answer? how many say, "no, it turns out "if you float in the great salt lake, "very, very dense water, but you know what? "the buoyant force gonna be just the same "if you float in there as if you float in the ocean, same buoyant force." how many say, "yes, that's true." hands? and who say, "that's not true." hands. mm-hmm.

maybe i leave that one for you to think about. [laughter] but i can give some hints. and i can say, "do you float in both cases?" - yeah. - yeah. hmm. isn't there a little room for floating? when something floats, the buoyant force will be how great? - equal to. - equal to. equal to what? - the weight. - the weight. so when you float in the great salt lake what's the buoyant-- let's suppose you're 120 pounder, what's the buoyant force on you? - 120 pounds. - 120 pounds. let's suppose you float in the lake, fresh water and you float. what's the buoyant force acting there if you're 120 pounder? - 120 pounds. - 120 pounds. so the buoyant force gonna be the same on both cases? - yeah. - yeah. question? wouldn't that because you float higher? you do float higher. all right. you float very high in the great salt lake. so, wouldn't that-- wouldn't you displace less water? yeah. you would displace very, very much less water, less volume of water. can we start to pull it together, gang?

can we pull these ideas together? you displace less volume of water. but salt lake water, honey, you don't have to have very much of it before it weighs the same as that what you would displace in the fresh water lake. you see the difference, gang? we're thinking carefully about these ideas. how much weight of water you displace, and how much volume of water you displace are two different ideas. and for the same weight and different densities, you have different volumes. okay, in a clay boat-- yeah. --and i made it big like that, it displaced more water. it displaced more water. and when i made the clay boat big, it displaced more water. and what happen to the buoyant force when i displaced more water? begin with an m. more. more. see? enough to make it float. okay. if you made it even flatter, will it displace it more? i can make it some more, but it sticks up above the top. i can do that. yeah. so the weight could stay the same? the weight's gonna stay the same. that's right. but the volume, i can change, the volume that the water stays. now, it's floating even higher. lee.

suppose that you filled it too much and the water got let into the air pocket inside-- ah. --what happens? then the weight is gonna increase. let's suppose there's a leak on the boat, huh, something like this. let's try this with a little hole there, okay? watch what happens now, gang. oh, it floats. it's very, very wonderful. but all of a sudden, it's getting heavier and heavier and-- [makes sounds] [laughter] okay? now, the buoyant force was-- wasn't enough to take care of that added weight. that's why when a boat springs a leak, it gets heavier. it gets heavier and the buoyant force no longer may be enough to make it float. lee, question. when you drop those bottles into the water a couple of weeks ago, a couple of sessions ago-- yes. --was there a buoyant force on the box? yeah. there's always a buoyant force on anything that displaces water, okay? now, how much buoyant force? equal to the volume. equal to--well, it's really equal to the--

the mass and weight of the bottle displaced by the water. that's right. that's right. yeah. when you're making that clay bigger, okay? by that equation, wouldn't it be changing its density? i'm changing--well-- because the weight stays the same with the volume. it's just the clay became bigger. so--and so the volume got-- the volume of the boat is way thicker than the water than you put it on. effectively, the density of that which does the displacing becomes less. the problem is that, well, the clay has the same density no matter what you do. that's true. but the volume of clay that displaces the water, that density becomes less because now a lot of it is that air. so in a sense, we're effectively changing the density. the density of a ship is a lot less dense than the density of iron and metal, because the ship has that open space in the middle. see? so the volume is way bigger by not increasing the weight if you hold the weight the same. do you see that these equations are nice ways to think about things? see?

if you hold the weight the same to change the volume, then you'll change the density. see, there's all kinds of ideas and considerations to think about with any problem. that's why these relationships at least narrow it down to a couple of things, in this case, to weight and volume. okay. consider you had a ship, like you own--you had a ship, --just like you have up on there. the weight increases, the volume also increases, right? i left you with question with a question, gang. what's gonna happen to a ship loaded with styrofoam compared to a ship that's empty? here's my ship empty. see how it floats? very high. see this styrofoam? how many say, "that ain't styrofoam." well, i can spread it out and pop it up and now it is. but it has the same weight, doesn't it? i put the styrofoam in. oh, that's strange. it sinks lower. let me ask you a question.

if you see a ship loaded with five tons of lead, is that gonna float lower in the water? yeah. how about you have the same ship loaded with five tons of styrofoam crumbed in there, is that gonna float lower in the water? yeah. guess which is heavier, five tons of lead or five tons of styrofoam? [laughter] so they're both gonna push the ship down by the same amount. so the answer is the ship loaded with anything that has any weight is gonna float lower than a ship loaded with nothing. did we kinda get that, gang? sure. here's the part where people get mixed up. what if you took that styrofoam and you attached it to the outside of the ship? what would happen then? it's gonna float higher. increase the volume. see, on the outside, you'd increase the volume. yeah. let's try something like this. here's a block of wood. it floats that high. what i'm gonna do is i'm gonna put this piece of metal.

get some elastic bands here. i'm gonna put a metal load on the top. and when i do that, is it gonna displace more water? yeah. yeah, it's gonna displace more water because it's heavier now. oops. still floating. let's get it sort of a little bit stable. you see how much this float, it's displacing, gang? see where that waterline is right to here? i'm gonna take this out and turn it upside-down. i'm gonna turn this upside-down. and you're gonna estimate where's the waterline gonna be, higher, lower or the same? - higher. - higher. - lower. - it's lower. how many say lower? how many say the same? how many say higher? how many say, "hey, i'm just gonna takes notes, right?" let's take a look, gang. it's floating, yeah? is this a floating object? how much water is it gonna be displaced by this floating object? some people say, "the weight of water displaced is equal to the weight of this." - yeah. - yeah. is this still equal to the weight of this? - yeah. - yeah. - the same. - it's the same. yeah. look, right there.

right. but you just increased the volume? yeah. did i? did i? did i increase the volume water displaced? no. there's a couple of ways to look at this. now, the iron is underneath. it is tricky. it is tricky. it's very, very something to really, really get you thinking, right? okay. it goes like that. it goes like this. you see in both cases, it's floating. notice how much-- notice how far down-- how far up the waterline is on the wood. that's because the whole weight of this is pushing down, yeah? well, this push down is hard when it's submerged? won't it buoyed up itself? yes. if you applied buoyant force on it. notice that the wood is a little higher now? yeah. but notice the water level over here is the same. there's a lot to think about there, gang, a lot.

and what i wanna do is i want to give you a couple of homework problems. problems, exercises, okay, that will help you shape up your thinking. say that--aren't the thing isn't attached to the wood, though, it's in the water, will the water rises the same amount? oh, if it wasn't attached, of course, and it would interact with the wood. you mean, like, it if were tied. no, if it wasn't. it was still in the water, the wood is in the water but separate. oh, well, then-- oh, i see what you're saying. okay, like over here. oh, your question is going to be very helpful to the question i'm gonna ask you. [laughter] so i won't answer you. the role of teachers are not to give answers. the role of teachers are to what? provoke questions. and who should be the one to remember and gets to find the answer? correct. see, it's tough that when you find the answers to your own questions, that's what you remember. and you might remember when you find the answers to someone else's question, which you'll hardly ever remember the answers that someone else's gives to their own questions.

so i want to ask you fellow-- you people a question and let you think about it for a couple of days. and here it is. i've got a boat, and the boat is loaded with metal. and look how low it floats. look where the waterline is here, gang. isn't that something? see the waterline? now, what i'm gonna do is i'm gonna take the metal out. when i take the metal out, what's the waterline do? it drops. but now, i'm gonna throw the metal back in. when i do that, will the waterline have a drop, rise, or stay where it was when i start it like that? that's your question. here's the waterline. when i take the metal out and throw it overboard,

overboard, will this water level go up, will it go down or will it stay right there? the thing to think about is now the metal is made to float. when i take it and throw it overboard, then the metal sinks. any difference in the buoyant force on the metal either way? something to think about. question without giving away too much information. well, if the water was all the way to the top and there was an ice cube inside, there's ice cubes floating, if the ice cube melt, would the water overflow? that's a good point. how about that, gang? you've got a glass of water with an ice cube in it. the ice cube sticks up a little bit, yeah?

when the ice cube melts, does the water level go higher, lower or stay the same? - higher. - it's higher. i'll be asking you that question at a different time. [laughter] too bad it's-- yeah. i got a nice one for you. you want a dandy? this is a dandy. okay. here's your question, gang. consider a balloon floating in the water. the balloon will float like that.

it will displace only a tiny bit of water. that tiny bit of water has some weight, yeah? guess what that weight of water is compared to the weight of the whole balloon? - equal. - equal, okay? so balloons float very, very high in the water, yeah? let's suppose this balloon, i weight it down. i tie a heavy brass weight on here, okay? and i make it float. i make it so it's just on the verge of sinking. here's my balloon right here. see that? see how that is? i mean, it is--the density of that balloon system, the balloon plus this now must be equal to that of water, just, just barely, yeah? i mean, on the verge of sinking like if i put a nickel or a dime on the top here, i'd increase the weight and that make it sink. but i'm not gonna do that. i have it just on the verge of sinking. now, here's your question. what would happen if i take that balloon

and i push it under the water by half a meter or so and take my hand away? when i do that, gang, what happens to the balloon? will the balloon stay there, will it sink or will it come back up? ooh. that's your question. that's your question. what will happen to the balloon when you push it under and let go? will it sink, stay where it is or come back up? and most important of all, hc, how come? any questions about anything, gang? yes. question. do we have to take into consideration the water pressure? oh, that will very, very much take into consideration, water pressure, very much. and if you don't that-- take that in consideration, then you will feel yuck, yuck, next time.

how about this, gang? someone says, "oh, the reason wood floats "and iron sinks is because wood-- because iron is heavier." i mean, you take a paper clip-- [makes sound] --then you take a great, big log and it floats. so what's that person mean when he says, "oh, it's because the iron is heavier?" - denser. - more dense. denser. denser. see? heavy compared to volume, then that's denser. any other questions about anything? okay, we're right on schedule, gang. next time, we're gonna be talking about gases, gases and atmospheric pressure. see you then. physics. yehey. [music]