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.

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welcome to another session of beliefs and believers. we certainly had quite an interesting class last time on buddhism, and i want to take a few more questions, because we're just getting