if you take the weight of this kid, very heavy kid times a small distance, you gonna get a number? that's gonna give you a torque like this. is there a way maybe to find out what the weight of the board is, if you knew this particular distance? and then, i want to give you something else to think about too, gang. see this broom? okay. where is the center of gravity of the broom? how many can see where the center of gravity is? is it in about here? all right, center of gravity right there? you see that? okay. here's what i'm gonna do, gang. right through the center of gravity. i got a question for you. if i put this in the bathroom scale,

which weighs more, this or this? or the same? think about that. if you know the answer to that, you know the difference between torque and weight. think about that. catch you next time. yay. [music]

you are bonkers 'cause iron doesn't float. people make boats out of wood. well, here's this clay, and it has the same weight. watch this. oh, yuck. [laughter] yucko. yeah, we got it now, gang. isn't that nice? now it's being held up by what? your fingers.

my fingers. you get the idea. concentration of force is pressure. so let's talk about that, gang. pressure, definition. screwed up. i don't wanna talk about pressure. i wanna talk about density first. you guys, can you come in on wednesday? [laughter] how do we find the center of gravity of different things? well, the book's easy. how about something like this? there's a way. and the way is very easy. let me show you. all i gotta do is suspend it. suspend it by that point. guess where the center of gravity is, gang? it's somewhere beneath this line, okay? over here,

somewhere in here. now, let me try this again, gang. troy, i think our board is insufficient. let me try this again. let me hold it from here, gang. the center of gravity is somewhere along there. and i can see if that's true by seeing if it will balance. and it does. so it's somewhere along there-- where along there? i can hang it by another point and find out that it's-- now, troy, the center of gravity of this board is within the board.

that blows everything, gang. i don't know what to do. yeah, the board's too fat. look at the globe here. in the summertime, amsterdam is way up here, okay? now, let's suppose we have an imaginary line right in here about where darkness is, okay? everything to this side here is dark, 'cause let's suppose the sun is coming in this way, okay? sunlight is coming in. well, let's look at amsterdam way up here. yeah, right here, okay? first of all, the sun comes up. here they are. day, day, day, day, day, day, day, day, day, day, day, day, day, day, day, day, night, night, night, night, night, night, night, day, day, day, day, day, day. most of the time, they're in the sunlight. the sun come right here. most--i've got this wrong. i've got this wrong, gang. i've been doing it.

in fact, when i get over here and started halfway, what? did you see i screwed up? i screwed up. what was my screw up? check the neighbor and see how hewitt screwed up. [laughter] how did hewitt screw up? come on, check the neighbor. how many are saying, "it looked all right to me." [laughter] come on. how did i screw up? you actually turned it over. yeah. turned it over. well, you gotta- well, for television-- okay, it's got 24 times as much area to feed itself. but what's wrong with that, gang? twenty-four times as much area is feeding how much more cell? 1, 2, 3, 4, 5, 6, 7, 8, eight times. oops. that was 24. yeah, it mixed up. yeah, eight times much. four times. oh, now, i mixed up, gang. i'm getting mixed up. it is four times as much total area, because 24 is four times six. four times six, that's why i screwed up.

what i'm gonna do? what i'm gonna do? how do we start that? thanks for bailing me out again, lee. what are we talking about-- i'm self-conscious when this camera is on me. the cell is getting bigger and bigger. huh? the cell is getting bigger and bigger. oh, yeah. [laughter] you guys get freaked out with this thing looking at you -how about me, yeah? [laughter] the living cell gets bigger and bigger, right? let's suppose the living cell gets double the size. slight, uh-huh-- what do we got here, gang? [laughter] what do we got here? trouble. i've got a tablecloth. i've got a tablecloth with no lip, okay? - no. - watch this. those dishes are essentially at rest, aren't they? here's something for you to do this weekend when you finally get invited to your friend's house for dinner, okay? and the friend wants to know, what are you doing, what are you doing at school? you can kind of show him this, right?

you don't wanna try this at your own house, not with your own dishes, okay? you might mess--but you try them at your friend's house. how about this, gang? what's gonna happen if i pull this thing very, very quickly, huh? what's gonna happen? -- let's try it. a one, a two, a three. and there you see newton's law flawlessly executed. that distinction between-- that distinction between weight and mass, i can kind of show you that kind of neatly with this device. what i'm gonna do is take this heavy ball-- heavy ball or massive ball? - both. - yes. both, yeah. see, i'm gonna take this ball. it's got a lot of mass, also has a lot of weight, okay? and what i'm gonna do, i'm gonna take one of these strings in the bottom. you see i'll try different trials here. and i'm gonna pull, pull, pull.

i'm gonna pull, pull, pull, pull, pull, pull, until one of these strings, either the bottom one or the top one, is gonna break. and what i want you to do is i want you to guess, hypothesize, which string, the top or the bottom will break with a gradual, gradual tension increased at the bottom? check your neighbor. okay, when i pull that very, very slowly, gang, which string gonna break, top or bottom? - top. - top. top one? how many say the top? let's try it. [laughter] maybe newton's having a bad day. [laughter] you know what that might have been? that might have been a string before that we partially damaged. yeah. probably. can we start the tape... but with an angle like that, doesn't it travel a greater distance than the one that's just falling vertically? so for them to hit the same time, it has to be going faster. the object has to be traveling faster.

it turns out, if i jump off the lanai like this, i'll step off like this. i'll step off like that. i'll hit at the same time in all places. over here, i'll be going faster, because i have a bigger speed like this. and that arrow is gonna be bigger than this and this. i'd be faster, but i've gone a further distance. - right. - okay. and later on we'll talk about a neat, neat concept that'll tell you that down here, the--wait a minute, i will not be going faster. erase the tape. lionel, that's wrong. it turns i'll have the same speed here, here and here. no, i won't either. no, i won't either. now, lionel, the tape's okay. leave it going. sorry. [laughter] i get a little mixed up. do you guys get mixed up with this stuff? i mean, all the time, i get mixed up with elementary physics. so if you guys get mixed up, don't feel bad. i'm with you, all right? with this clip, i'm gonna fasten the point to here. now, i'm gonna crank this again, okay?

if you see a lightning bolt from here to here, if you see that, scouts honor, "a" in the course. if you don't see that, then you got to do your exams and study and da, da, da, da, okay? so let's try it now. [laughter] i've seen it. scouts honor. scouts honor. never go back on a scout's honor. [laughter] oh, boy. [laughter] it's almost as if there's a spark there, isn't there? [laughter] this is most unusual. i think i see-- try switching the other side.

no. and, gang, i have no explanation for this. this is new to me. can you put it on the other side? this should--it should be less probable, though, but-- you see it's got to leak from one to the other. i wonder if it's because i didn't discharge it to begin with. let me try something. --continuing to charge. isn't that in a way-- yeah, it does. it turns out it does, yeah. but i could--you crank it counter clockwise. okay, watch this now. it shouldn't do. [laughter] that blows me out. that blows me out. this has never happened before. i've never noticed-- and if the leak's off that point, then it should drift over here without having that snap, snap, snap, and it's not happening. try to--when you put the two points on it, you turn it the other the way. oh, well, i didn't mean to do that, but... see if it works--

now, but that-- maybe you should discharge it first. [laughter] oh my god. [laughter] i noticed everyone out there seems to be pretty happy today. [laughter] you seem to be pretty happy because you see the old fool up here making a damned fool of himself, right? you guys should all be saying, "oh, gee--so we could-- "yeah, we can test to see whether things are *true. "if i bring a positive--i bring a positive object nearby, "shouldn't the positive object attract the negatives and pull the negatives from there? mm-hmm. and shouldn't the leads collapse? one of the nice things about science is you start to understand and see if you can predict things. and if you can, then it tells you that your theory probably is more likely correct than more likely wrong. let's try that, gang. if this is more positive--

oh my god. [laughter] why does it still diverge more? that blows me away, gang. is that coming together? it's getting more and more diversion. and it should collapse when i bring this over. it should. what do you mean it should? it's doing what it should. my explanation is just off, right? [laughter] look at that. i've got nothing to-- i'm supposed to be teaching you guys electrostatics. i've got nothing to say. in fact, probably everything i say is just all canned crap. [laughter] because, honey, it's just not doing. look at that. i've got nothing to say. i could talk about coulomb's law a little bit, but i don't believe in it anymore. [laughter] let's continue as if everything were going smooth.

it's called make believe. i thought science was all about making discoveries, experimental and-- we could continue with this, couldn't we? we could continue and maybe find something fundamental, but it's not part of my act. [laughter] well, okay, let's move on, gang. i don't know. someone's gonna give me an explanation of what's happening here. and i'm gonna be very impressed. who is going to be the one? in fact, that could be like a term project. what went wrong tonight? who's gonna say, "hewitt, nothing went wrong at all. "what happened was, da, da, da, da, da, da, da. "what went wrong was your failure "to be able to observe and interpret what happened to it. da, da, da, da, da. nature is not wrong, you is." okay?

someone write it out, 'cause i am baffled, gang. [music]