[Script Info] Title: [Events] Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text Dialogue: 0,0:00:00.00,0:00:03.87,Default,,0000,0000,0000,,The following content is provided under a Creative Commons license. Dialogue: 0,0:00:03.87,0:00:06.57,Default,,0000,0000,0000,,Your support will help MIT OpenCourseWare continue Dialogue: 0,0:00:06.57,0:00:13.40,Default,,0000,0000,0000,,to offer high-quality educational resources for free. To make a donation or to view additional material Dialogue: 0,0:00:13.40,0:00:15.29,Default,,0000,0000,0000,,from hundreds of MIT courses, Dialogue: 0,0:00:15.29,0:00:20.55,Default,,0000,0000,0000,,visit MIT OpenCourseWare at ocw.mit.edu. Dialogue: 0,0:00:21.11,0:00:26.95,Default,,0000,0000,0000,,Due to technical difficulties, only a portion of lecture 1 is available for viewing Dialogue: 0,0:00:26.95,0:00:31.09,Default,,0000,0000,0000,,Welcome to Teaching College-Level Science and Engineering. Dialogue: 0,0:00:31.09,0:00:36.32,Default,,0000,0000,0000,,Now, the title contains the word "teaching," which may spark some questions in your mind. Dialogue: 0,0:00:36.32,0:00:43.91,Default,,0000,0000,0000,,For example, is teaching just an art? Or is it something that's just - something you're born with. Dialogue: 0,0:00:43.91,0:00:49.46,Default,,0000,0000,0000,,In which case, either you have it or you don't have it. Well, obviously I don't believe that Dialogue: 0,0:00:49.46,0:00:51.98,Default,,0000,0000,0000,,or I wouldn't be teaching a course on it. Dialogue: 0,0:00:51.98,0:00:52.85,Default,,0000,0000,0000,,What would be the point? Dialogue: 0,0:00:52.85,0:00:59.01,Default,,0000,0000,0000,,Or is it purely a science, where there's a set of equations and procedures to learn, Dialogue: 0,0:00:59.01,0:01:02.07,Default,,0000,0000,0000,,and then all of a sudden you'll be an excellent teacher? Dialogue: 0,0:01:02.07,0:01:08.84,Default,,0000,0000,0000,,Well, actually, it's neither and it's both. It's things that we're all born with, Dialogue: 0,0:01:08.84,0:01:13.75,Default,,0000,0000,0000,,on the one hand, and they're also procedures and techniques, and ways of thinking Dialogue: 0,0:01:13.75,0:01:17.01,Default,,0000,0000,0000,,that will improve how you teach, and that we can all learn. Dialogue: 0,0:01:17.01,0:01:20.06,Default,,0000,0000,0000,,So it's a happy mix, my favorite mix, Dialogue: 0,0:01:20.06,0:01:29.27,Default,,0000,0000,0000,,an art and a science. So, for example, another example that's an art and a science is book design. Dialogue: 0,0:01:29.27,0:01:36.32,Default,,0000,0000,0000,,So compared for example to just pure art, painting, say modern painting, very unconstrained Dialogue: 0,0:01:36.32,0:01:40.54,Default,,0000,0000,0000,,vs. say, biology procedures in the laboratory Dialogue: 0,0:01:40.54,0:01:48.77,Default,,0000,0000,0000,,you know, very very closely specified. It's somewhere in between there is an art but there is, of all Dialogue: 0,0:01:48.77,0:01:54.21,Default,,0000,0000,0000,,of the arts, of colors, of space, but they all have to Dialogue: 0,0:01:54.21,0:02:01.96,Default,,0000,0000,0000,,be used together to achieve a particular purpose. So, again, there are some beautifully designed books and Dialogue: 0,0:02:01.96,0:02:05.86,Default,,0000,0000,0000,,some not so beautifully designed books. And there are principles behind that that we can use to design good books. Dialogue: 0,0:02:07.66,0:02:11.92,Default,,0000,0000,0000,,Simiilarly, there are principles we can use to design good teaching. Dialogue: 0,0:02:11.93,0:02:15.82,Default,,0000,0000,0000,,So this is the whole point of this semester is to design good teaching and how you do that. Dialogue: 0,0:02:17.16,0:02:20.14,Default,,0000,0000,0000,,And rather than give you a big long theory about it, Dialogue: 0,0:02:20.14,0:02:22.50,Default,,0000,0000,0000,,because actually there isn't really theory Dialogue: 0,0:02:22.50,0:02:26.42,Default,,0000,0000,0000,,so much in the equivalent to say Einstein's theory of relativity, Dialogue: 0,0:02:26.42,0:02:29.14,Default,,0000,0000,0000,,but there's principles to learn. Dialogue: 0,0:02:29.25,0:02:31.65,Default,,0000,0000,0000,,The best way to learn those principles is Dialogue: 0,0:02:32.36,0:02:34.04,Default,,0000,0000,0000,,with an example. Dialogue: 0,0:02:34.04,0:02:35.99,Default,,0000,0000,0000,,So what we're gonna do today is Dialogue: 0,0:02:35.99,0:02:40.64,Default,,0000,0000,0000,,I'm going to do an example of teaching with you. Dialogue: 0,0:02:40.64,0:02:46.44,Default,,0000,0000,0000,,We're gonna do it slightly sped-up version of what we'd normally do Dialogue: 0,0:02:46.44,0:02:49.26,Default,,0000,0000,0000,,say if we were actually using this example in a class. Dialogue: 0,0:02:49.26,0:02:52.18,Default,,0000,0000,0000,,Then we're gonna analyze why it was done that way. Dialogue: 0,0:02:52.18,0:02:56.01,Default,,0000,0000,0000,,and from an analysis, general principles of teaching will come out Dialogue: 0,0:02:56.01,0:02:59.04,Default,,0000,0000,0000,,that will be address throughout the semester Dialogue: 0,0:02:59.04,0:03:03.65,Default,,0000,0000,0000,,and they'll be addressed in the context of particular tasks, Dialogue: 0,0:03:03.65,0:03:08.12,Default,,0000,0000,0000,,for example, how to make slides that are useful for teaching. Dialogue: 0,0:03:08.12,0:03:10.82,Default,,0000,0000,0000,,How to use a blackboard. Dialogue: 0,0:03:10.82,0:03:12.61,Default,,0000,0000,0000,,How to teach equations. Dialogue: 0,0:03:12.66,0:03:14.70,Default,,0000,0000,0000,,How to design a whole course. Dialogue: 0,0:03:14.70,0:03:16.06,Default,,0000,0000,0000,,How to make problems. Dialogue: 0,0:03:16.06,0:03:20.48,Default,,0000,0000,0000,,So all of those tasks will be the week-by-week subjects Dialogue: 0,0:03:20.48,0:03:23.91,Default,,0000,0000,0000,,and in each task, all the principles that we're gonna talk about now Dialogue: 0,0:03:23.91,0:03:30.98,Default,,0000,0000,0000,,will show up in those tasks and you'll see the principles illustrated repeatedly. Dialogue: 0,0:03:30.98,0:03:35.20,Default,,0000,0000,0000,,So, the problem. One of my favorites, Dialogue: 0,0:03:36.74,0:03:38.75,Default,,0000,0000,0000,,so these are two cones Dialogue: 0,0:03:39.87,0:03:42.69,Default,,0000,0000,0000,,one is -- has twice the dimensions of the other cones. Dialogue: 0,0:03:42.69,0:03:46.63,Default,,0000,0000,0000,,So let me show you how I made the cones. Dialogue: 0,0:03:50.39,0:03:55.18,Default,,0000,0000,0000,,So I printed out a circle and just cut out Dialogue: 0,0:03:55.18,0:03:57.57,Default,,0000,0000,0000,,one quarter of the circle Dialogue: 0,0:03:58.19,0:04:00.63,Default,,0000,0000,0000,,and then I taped this edge to that edge. Dialogue: 0,0:04:05.81,0:04:10.28,Default,,0000,0000,0000,,Or in mathematician speak, I identified the edges Dialogue: 0,0:04:10.98,0:04:14.01,Default,,0000,0000,0000,,which I now know means I taped the edges together. Dialogue: 0,0:04:14.14,0:04:16.30,Default,,0000,0000,0000,,and then you get a cone like that. Dialogue: 0,0:04:17.03,0:04:20.76,Default,,0000,0000,0000,,So this cone and the other cone were cut out of the same sheet of paper Dialogue: 0,0:04:20.76,0:04:25.40,Default,,0000,0000,0000,,except this one has twice the linear dimensions in its circle. Dialogue: 0,0:04:25.40,0:04:32.35,Default,,0000,0000,0000,,This circle was seven centimeters in radius and this is three and a half centimeters in radius. Dialogue: 0,0:04:33.84,0:04:36.03,Default,,0000,0000,0000,,Other than that, they're the same. Dialogue: 0,0:04:36.03,0:04:42.30,Default,,0000,0000,0000,,The question is which one has the higher terminal of velocity or are they more comparable. Dialogue: 0,0:04:42.78,0:04:43.65,Default,,0000,0000,0000,,So the question is this. Dialogue: 0,0:04:44.80,0:04:47.56,Default,,0000,0000,0000,,I'm gonna drop them and the question is Dialogue: 0,0:04:47.56,0:04:50.87,Default,,0000,0000,0000,,what is the ratio of their terminal velocities? Dialogue: 0,0:05:01.62,0:05:06.47,Default,,0000,0000,0000,,So the ratio of the big cone's terminal velocity to the small cone's terminal velocity Dialogue: 0,0:05:06.47,0:05:13.95,Default,,0000,0000,0000,,is equals to what and you get choices along this axis Dialogue: 0,0:05:13.95,0:05:38.37,Default,,0000,0000,0000,,So here is... Dialogue: 0,0:05:38.37,0:05:42.27,Default,,0000,0000,0000,,Okay, so those are the five regions to choose from. Dialogue: 0,0:05:46.91,0:05:49.14,Default,,0000,0000,0000,,So you have five choices for the ratio Dialogue: 0,0:05:49.14,0:05:51.41,Default,,0000,0000,0000,,roughly one quarter Dialogue: 0,0:05:51.41,0:05:53.82,Default,,0000,0000,0000,,some range here, because nothing's exact Dialogue: 0,0:05:53.82,0:05:55.97,Default,,0000,0000,0000,,and we're definitely not gonna do an exact experiment. Dialogue: 0,0:05:56.91,0:06:01.60,Default,,0000,0000,0000,,Roughly one half, roughly one, roughly two, or roughly four. Dialogue: 0,0:06:01.60,0:06:04.68,Default,,0000,0000,0000,,So does everyone understand the question? Dialogue: 0,0:06:04.68,0:06:06.23,Default,,0000,0000,0000,,You're gonna get to try it yourself. Dialogue: 0,0:06:08.54,0:06:10.24,Default,,0000,0000,0000,,Question about the question Dialogue: 0,0:06:10.50,0:06:13.94,Default,,0000,0000,0000,,I don't know if you could restate the question... actually there was a signing sheet going around... and I sorta lost it. Dialogue: 0,0:06:16.80,0:06:20.05,Default,,0000,0000,0000,,So, uh, yeah, can I restate the question, no problem. Dialogue: 0,0:06:20.05,0:06:22.28,Default,,0000,0000,0000,,So I'm gonna drop them Dialogue: 0,0:06:22.57,0:06:24.20,Default,,0000,0000,0000,,just like this no tricks, Dialogue: 0,0:06:24.20,0:06:27.53,Default,,0000,0000,0000,,I'm not gonna flip this one around or anything. Dialogue: 0,0:06:27.53,0:06:30.86,Default,,0000,0000,0000,,And the question is, what's the ratio of their terminal speeds. Dialogue: 0,0:06:30.86,0:06:33.44,Default,,0000,0000,0000,,So right away, as soon as you let go of them, Dialogue: 0,0:06:33.44,0:06:36.05,Default,,0000,0000,0000,,they come to a steady speed, Dialogue: 0,0:06:36.05,0:06:37.81,Default,,0000,0000,0000,,which is their terminal velocity. Dialogue: 0,0:06:37.81,0:06:42.20,Default,,0000,0000,0000,,And the question is how do the terminal speeds of the big one and the small one differ. Dialogue: 0,0:06:42.83,0:06:46.14,Default,,0000,0000,0000,,So in particular, the question is what's the ratio? Dialogue: 0,0:06:46.14,0:06:47.98,Default,,0000,0000,0000,,And there's five choices for them. Dialogue: 0,0:06:49.07,0:06:49.92,Default,,0000,0000,0000,,Okay. Dialogue: 0,0:06:49.92,0:06:51.27,Default,,0000,0000,0000,,That help? Dialogue: 0,0:06:51.27,0:06:53.98,Default,,0000,0000,0000,,-Yes, and what were the dimensions of them again. Dialogue: 0,0:06:53.98,0:07:00.33,Default,,0000,0000,0000,,-So this guy is -- he was cut out of a circle who was 7 centimeters in radius. Dialogue: 0,0:07:00.33,0:07:05.80,Default,,0000,0000,0000,,And this guy was cut out of a circle who was 3.5 centimeters in radius. Dialogue: 0,0:07:05.80,0:07:09.100,Default,,0000,0000,0000,,And then I was also very careful to use-- do this right?-- Dialogue: 0,0:07:09.100,0:07:15.25,Default,,0000,0000,0000,,I used half the width of tape on the small guy as I did on the big guy Dialogue: 0,0:07:15.25,0:07:21.09,Default,,0000,0000,0000,,just to get it really very perfect scale. Dialogue: 0,0:07:21.09,0:07:27.16,Default,,0000,0000,0000,,Any questions about the question? Dialogue: 0,0:07:27.18,0:07:31.18,Default,,0000,0000,0000,,Okay, so think for yourself for about 30 seconds or so Dialogue: 0,0:07:31.18,0:07:34.52,Default,,0000,0000,0000,,just to induct yourself into the problem Dialogue: 0,0:07:34.52,0:07:36.29,Default,,0000,0000,0000,,and then we'll take a vote. Dialogue: 0,0:07:36.29,0:08:13.75,Default,,0000,0000,0000,,And then you'll have a chance to discuss it with each other. Dialogue: 0,0:08:18.74,0:08:20.40,Default,,0000,0000,0000,,Okay, let's just take a vote Dialogue: 0,0:08:20.40,0:08:29.29,Default,,0000,0000,0000,,so I understand I haven't given all of you enough time to come up with an exact answer or calculate anything. Dialogue: 0,0:08:29.32,0:08:34.79,Default,,0000,0000,0000,,So let's just get a straw poll and then you'll have a chance to argue about it with your neighbor. Dialogue: 0,0:08:34.79,0:08:38.44,Default,,0000,0000,0000,,So who votes for 1/4 which is-- Dialogue: 0,0:08:38.44,0:08:42.12,Default,,0000,0000,0000,,so let's see-- 1, 2, 3, 4, 5, 6. Dialogue: 0,0:08:44.14,0:08:47.96,Default,,0000,0000,0000,,Who votes for 1/2? Dialogue: 0,0:08:47.96,0:08:54.47,Default,,0000,0000,0000,,[counts] 12 Dialogue: 0,0:08:54.47,0:08:57.80,Default,,0000,0000,0000,,Who votes for C? Dialogue: 0,0:08:57.80,0:09:01.49,Default,,0000,0000,0000,,About 22. Dialogue: 0,0:09:01.49,0:09:04.28,Default,,0000,0000,0000,,Who votes for D? Dialogue: 0,0:09:04.28,0:09:05.62,Default,,0000,0000,0000,,No takers. Dialogue: 0,0:09:05.62,0:09:06.91,Default,,0000,0000,0000,,No takers for D. Dialogue: 0,0:09:06.91,0:09:11.13,Default,,0000,0000,0000,,How about E? Dialogue: 0,0:09:11.13,0:09:13.36,Default,,0000,0000,0000,,Okay, so Dialogue: 0,0:09:13.36,0:09:15.38,Default,,0000,0000,0000,,now find a neighbor or two, Dialogue: 0,0:09:15.38,0:09:16.72,Default,,0000,0000,0000,,one or two neighbors, Dialogue: 0,0:09:16.72,0:09:18.52,Default,,0000,0000,0000,,introduce yourself to your neighbor, Dialogue: 0,0:09:18.52,0:09:21.53,Default,,0000,0000,0000,,and also by the way, unless you're taking notes on your laptop, Dialogue: 0,0:09:21.53,0:09:27.30,Default,,0000,0000,0000,,if you could close your laptop, that would be very helpful for the purpose of discussion in this whole Dialogue: 0,0:09:27.30,0:09:28.04,Default,,0000,0000,0000,,course. Dialogue: 0,0:09:28.70,0:09:31.95,Default,,0000,0000,0000,,So find a neighbor or two, introduce yourself, Dialogue: 0,0:09:31.95,0:09:37.65,Default,,0000,0000,0000,,you'll be given a chance to meet graduate students from across te institute, Dialogue: 0,0:09:37.65,0:09:39.75,Default,,0000,0000,0000,,and try to convince them about your answer. Dialogue: 0,0:09:39.75,0:09:40.91,Default,,0000,0000,0000,,Especially if you have a different answer. Dialogue: 0,0:09:40.91,0:09:45.07,Default,,0000,0000,0000,,Or if you happen to share an answer, try to figure out why you're sure of it Dialogue: 0,0:09:45.07,0:09:48.16,Default,,0000,0000,0000,,or if you're not sure of it, settle... Dialogue: 0,0:09:48.16,0:09:50.69,Default,,0000,0000,0000,,So, discussion time. Dialogue: 0,0:09:50.69,0:09:54.36,Default,,0000,0000,0000,,And if you have any questions that come up as you're discussing, Dialogue: 0,0:09:54.36,0:09:56.47,Default,,0000,0000,0000,,raise your hand and I'll come and wonder over. Dialogue: 0,0:09:58.52,0:10:01.46,Default,,0000,0000,0000,,Okay, so meanwhile I also handed out Dialogue: 0,0:10:01.46,0:10:04.32,Default,,0000,0000,0000,,feedback sheets for the end of the session Dialogue: 0,0:10:04.32,0:10:07.40,Default,,0000,0000,0000,,which I'll ask you to spend a minute on at the end. Dialogue: 0,0:10:07.40,0:10:11.48,Default,,0000,0000,0000,,You'll notice one of the question is what's the most confusing thing? Dialogue: 0,0:10:11.48,0:10:14.52,Default,,0000,0000,0000,,So if anything really confusing comes up during the whole session, Dialogue: 0,0:10:14.52,0:10:17.32,Default,,0000,0000,0000,,you can just put it right there, you don't have to wait until the end, Dialogue: 0,0:10:17.32,0:10:19.65,Default,,0000,0000,0000,,or if there's something you really liked or hated, Dialogue: 0,0:10:19.65,0:10:22.46,Default,,0000,0000,0000,,that's question 2, you can put whenever to come up. Dialogue: 0,0:10:22.73,0:10:26.76,Default,,0000,0000,0000,,But, vote #2 and then we'll take some reasons... Dialogue: 0,0:10:26.76,0:10:29.44,Default,,0000,0000,0000,,so... Dialogue: 0,0:10:29.44,0:10:32.50,Default,,0000,0000,0000,,One quarter. Dialogue: 0,0:10:32.50,0:10:36.37,Default,,0000,0000,0000,,One, two, three. Dialogue: 0,0:10:36.37,0:10:39.36,Default,,0000,0000,0000,,Okay, four. Dialogue: 0,0:10:39.36,0:10:41.94,Default,,0000,0000,0000,,One half. Dialogue: 0,0:10:41.94,0:10:44.23,Default,,0000,0000,0000,,Halves don't have it. Dialogue: 0,0:10:44.23,0:10:48.37,Default,,0000,0000,0000,,There's one... okay great. 4, 5, 6. Dialogue: 0,0:10:49.25,0:10:50.90,Default,,0000,0000,0000,,Equall. Dialogue: 0,0:10:51.76,0:10:54.15,Default,,0000,0000,0000,,Let's call it 30. Dialogue: 0,0:10:54.15,0:10:58.18,Default,,0000,0000,0000,,Two Dialogue: 0,0:10:58.18,0:11:00.83,Default,,0000,0000,0000,,and four. Dialogue: 0,0:11:00.83,0:11:03.26,Default,,0000,0000,0000,,Okay, so Dialogue: 0,0:11:03.26,0:11:04.94,Default,,0000,0000,0000,,thanks for the votes. Dialogue: 0,0:11:04.94,0:11:07.04,Default,,0000,0000,0000,,Let's take reasons for any of them. Dialogue: 0,0:11:07.04,0:11:09.74,Default,,0000,0000,0000,,I'll take reasons for any of them, I'll put them up here. Dialogue: 0,0:11:09.74,0:11:11.50,Default,,0000,0000,0000,,You don't even have to agree with the reasons, Dialogue: 0,0:11:11.50,0:11:14.48,Default,,0000,0000,0000,,just something you guys discussed and something that was plausible. Dialogue: 0,0:11:14.48,0:11:17.47,Default,,0000,0000,0000,,-C... Dialogue: 0,0:11:17.47,0:11:20.04,Default,,0000,0000,0000,,-Oh.... Dialogue: 0,0:11:21.29,0:11:23.85,Default,,0000,0000,0000,,-When you do these activities, Dialogue: 0,0:11:23.85,0:11:27.65,Default,,0000,0000,0000,,there's always some... [indistinct] Dialogue: 0,0:11:27.65,0:11:30.28,Default,,0000,0000,0000,,I want to know what you would do in that kind of situation. Dialogue: 0,0:11:30.28,0:11:33.58,Default,,0000,0000,0000,,-So, you're hmm... Dialogue: 0,0:11:33.58,0:11:35.39,Default,,0000,0000,0000,,[laughter] I'm not sure how to phrase this. Dialogue: 0,0:11:35.39,0:11:37.76,Default,,0000,0000,0000,,Uh... Dialogue: 0,0:11:37.76,0:11:39.59,Default,,0000,0000,0000,,Let me just take other comments. Dialogue: 0,0:11:39.59,0:11:41.80,Default,,0000,0000,0000,,[laughter] Dialogue: 0,0:11:41.80,0:11:43.61,Default,,0000,0000,0000,,I'll come to it afterwards. Dialogue: 0,0:11:43.61,0:11:45.26,Default,,0000,0000,0000,,Other comments Dialogue: 0,0:11:45.26,0:11:46.96,Default,,0000,0000,0000,,for any of the reasons. Dialogue: 0,0:11:46.96,0:11:48.48,Default,,0000,0000,0000,,So again, it doesn't have to be anything you necessarily believe Dialogue: 0,0:11:48.48,0:11:50.28,Default,,0000,0000,0000,,but things that are plausible Dialogue: 0,0:11:50.28,0:11:54.13,Default,,0000,0000,0000,,and that's actually more instructive than what you think is for sure right, Dialogue: 0,0:11:54.13,0:11:58.12,Default,,0000,0000,0000,,because you're trying to figure out what might be true and you're expanding Dialogue: 0,0:11:58.12,0:11:59.69,Default,,0000,0000,0000,,the ways you're thinking. Dialogue: 0,0:11:59.69,0:12:06.16,Default,,0000,0000,0000,,-C, because they have identical mass to certain... Dialogue: 0,0:12:06.16,0:12:11.77,Default,,0000,0000,0000,,-C, so mass-to-area ratio is the same. Dialogue: 0,0:12:13.71,0:12:19.03,Default,,0000,0000,0000,,Okay, can people think of plausible reasons against that argument? Dialogue: 0,0:12:20.74,0:12:21.69,Default,,0000,0000,0000,,Yes. Dialogue: 0,0:12:21.69,0:12:23.85,Default,,0000,0000,0000,,-I have no idea what the actual formula is. Dialogue: 0,0:12:23.85,0:12:24.64,Default,,0000,0000,0000,,-Right. Dialogue: 0,0:12:24.64,0:12:29.64,Default,,0000,0000,0000,,-There was a square there... Dialogue: 0,0:12:29.64,0:12:32.62,Default,,0000,0000,0000,,-Right, so I'll call this not C. Dialogue: 0,0:12:32.62,0:12:36.89,Default,,0000,0000,0000,,So supposedly, formual actually depended on the square root of A Dialogue: 0,0:12:36.89,0:12:39.56,Default,,0000,0000,0000,,or something like that. Dialogue: 0,0:12:39.56,0:12:44.20,Default,,0000,0000,0000,,You know maybe---- say, one chance out of three that it has A to the first power here. Dialogue: 0,0:12:44.20,0:12:48.06,Default,,0000,0000,0000,,It could have A to the 1/2 or 8 to the 2. Dialogue: 0,0:12:48.63,0:12:50.90,Default,,0000,0000,0000,,So, could be... Dialogue: 0,0:12:57.41,0:12:58.79,Default,,0000,0000,0000,,A to the k Dialogue: 0,0:12:58.79,0:13:03.01,Default,,0000,0000,0000,,M over A to the K for K not equal to one. Dialogue: 0,0:13:03.01,0:13:05.02,Default,,0000,0000,0000,,Okay, others. Dialogue: 0,0:13:05.02,0:13:12.07,Default,,0000,0000,0000,,4 against C, intuitive reasons, or for any of the others. Dialogue: 0,0:13:17.77,0:13:20.64,Default,,0000,0000,0000,,Okay, so hopefully that's... Dialogue: 0,0:13:20.69,0:13:23.60,Default,,0000,0000,0000,,-[indistinct] Dialogue: 0,0:13:23.60,0:13:27.68,Default,,0000,0000,0000,,...that air resistance goes with the area Dialogue: 0,0:13:27.68,0:13:31.28,Default,,0000,0000,0000,,and the gravitational force... Dialogue: 0,0:13:31.28,0:13:33.100,Default,,0000,0000,0000,,-Okay, so let's see. Dialogue: 0,0:13:33.100,0:13:42.40,Default,,0000,0000,0000,,F drag partial to area and weight. Dialogue: 0,0:13:42.40,0:13:44.07,Default,,0000,0000,0000,,So that's the argument for which choice? Dialogue: 0,0:13:44.07,0:13:46.68,Default,,0000,0000,0000,,For C, okay. Dialogue: 0,0:13:47.96,0:13:51.13,Default,,0000,0000,0000,,How do you know that the drab scales are the area. Dialogue: 0,0:13:51.13,0:13:54.94,Default,,0000,0000,0000,,Maybe the scales with the square root of area. Dialogue: 0,0:13:57.82,0:14:02.67,Default,,0000,0000,0000,,Any argument pro or con? Dialogue: 0,0:14:05.12,0:14:07.68,Default,,0000,0000,0000,,Okay, yeah. Dialogue: 0,0:14:07.68,0:14:14.66,Default,,0000,0000,0000,,-scales with the area...you can just break it up... Dialogue: 0,0:14:14.66,0:14:18.52,Default,,0000,0000,0000,,-Okay, so there's a .... Dialogue: 0,0:14:18.52,0:14:22.99,Default,,0000,0000,0000,,So for this, let's say there's a ... for subdividing Dialogue: 0,0:14:22.99,0:14:26.29,Default,,0000,0000,0000,,I'll just know that is subdividing. Dialogue: 0,0:14:31.55,0:14:34.43,Default,,0000,0000,0000,,Okay, yeah. Dialogue: 0,0:14:34.43,0:14:38.40,Default,,0000,0000,0000,,-Some weird shape... and then go to the rest of the pieces so... Dialogue: 0,0:14:38.40,0:14:42.95,Default,,0000,0000,0000,,-So it may depend on the division--I mean, the geometry, Dialogue: 0,0:14:42.95,0:14:45.72,Default,,0000,0000,0000,,so I'll put that here as geometry. Dialogue: 0,0:14:52.13,0:14:54.51,Default,,0000,0000,0000,,What else might it depend on? Dialogue: 0,0:14:54.52,0:15:00.11,Default,,0000,0000,0000,,For example, is air resistance say always proportional to area? Dialogue: 0,0:15:02.11,0:15:03.29,Default,,0000,0000,0000,,Hmm. Dialogue: 0,0:15:04.67,0:15:05.71,Default,,0000,0000,0000,,Yeah? Dialogue: 0,0:15:07.04,0:15:09.04,Default,,0000,0000,0000,,-...Depend on the material of the surface. Dialogue: 0,0:15:09.04,0:15:12.34,Default,,0000,0000,0000,,-Okay, so it might depend on the material Dialogue: 0,0:15:12.34,0:15:16.83,Default,,0000,0000,0000,,and it certainly does, which is actually why I was careful Dialogue: 0,0:15:16.83,0:15:18.88,Default,,0000,0000,0000,,to construct them out of the same piece of paper, Dialogue: 0,0:15:18.88,0:15:21.74,Default,,0000,0000,0000,,so let me put this. Dialogue: 0,0:15:21.74,0:15:24.84,Default,,0000,0000,0000,,Material... Dialogue: 0,0:15:24.84,0:15:28.08,Default,,0000,0000,0000,,So the surface roughness. Dialogue: 0,0:15:28.08,0:15:30.96,Default,,0000,0000,0000,,[indisctinct question] Dialogue: 0,0:15:33.56,0:15:36.00,Default,,0000,0000,0000,,-Okay, so whether they fall vertically or downward. Dialogue: 0,0:15:36.00,0:15:37.37,Default,,0000,0000,0000,,Yeah, that's true. Dialogue: 0,0:15:37.37,0:15:40.04,Default,,0000,0000,0000,,So it might depend on the way I drop them. Dialogue: 0,0:15:40.04,0:15:42.23,Default,,0000,0000,0000,,So to make us not have to worry about that, Dialogue: 0,0:15:42.23,0:15:46.81,Default,,0000,0000,0000,,I'll just drop them simultaniously, pointing downward. Dialogue: 0,0:15:46.83,0:15:52.54,Default,,0000,0000,0000,,So the fall configuration. Dialogue: 0,0:15:52.60,0:15:57.02,Default,,0000,0000,0000,,So there's all these other variables. Dialogue: 0,0:15:57.02,0:15:59.36,Default,,0000,0000,0000,,Okay, so let's do the experiment and then I'll come back to your question. Dialogue: 0,0:15:59.36,0:16:05.95,Default,,0000,0000,0000,,Okay, so let's do the experiement this way Dialogue: 0,0:16:09.97,0:16:14.41,Default,,0000,0000,0000,,so I'll stand on the table Dialogue: 0,0:16:14.41,0:16:23.10,Default,,0000,0000,0000,,and pray that I have matching socks on with is sort of 80% these days. Dialogue: 0,0:16:23.10,0:16:26.36,Default,,0000,0000,0000,,It's increased. Dialogue: 0,0:16:26.36,0:16:28.16,Default,,0000,0000,0000,,And I will drop them on the count of 3. Dialogue: 0,0:16:28.16,0:16:29.34,Default,,0000,0000,0000,,1-- Dialogue: 0,0:16:29.34,0:16:33.86,Default,,0000,0000,0000,,Are they both, the points, about the same level? Dialogue: 0,0:16:33.86,0:16:35.78,Default,,0000,0000,0000,,They look sort of to me but Dialogue: 0,0:16:35.78,0:16:40.91,Default,,0000,0000,0000,,my depth perception is actually quite bad Dialogue: 0,0:16:40.91,0:16:43.31,Default,,0000,0000,0000,,so is that about equal? Dialogue: 0,0:16:43.31,0:16:46.98,Default,,0000,0000,0000,,Okay, so 1, 2, 3. Dialogue: 0,0:16:46.98,0:16:48.71,Default,,0000,0000,0000,,Simulateous. Dialogue: 0,0:16:48.71,0:16:52.90,Default,,0000,0000,0000,,Okay, so there you have choice C. Dialogue: 0,0:16:52.96,0:16:55.25,Default,,0000,0000,0000,,Interesting consequence of that. Dialogue: 0,0:16:55.25,0:16:58.30,Default,,0000,0000,0000,,So what that shows is that Dialogue: 0,0:16:58.30,0:17:01.84,Default,,0000,0000,0000,,drag in this case is proportional to area. Dialogue: 0,0:17:01.84,0:17:05.51,Default,,0000,0000,0000,,It turns out, that that's not always the case. Dialogue: 0,0:17:05.51,0:17:08.42,Default,,0000,0000,0000,,So drag very often, Dialogue: 0,0:17:08.42,0:17:10.26,Default,,0000,0000,0000,,well, not very often in everyday life, Dialogue: 0,0:17:10.26,0:17:16.18,Default,,0000,0000,0000,,but very easily can be proportional to... Dialogue: 0,0:17:20.84,0:17:23.12,Default,,0000,0000,0000,,proportional to size. Dialogue: 0,0:17:23.12,0:17:26.64,Default,,0000,0000,0000,,And you don't know ahead of time which one it's gonna be. Dialogue: 0,0:17:26.64,0:17:30.85,Default,,0000,0000,0000,,So it vari--- so it turns out at slow speeds, Dialogue: 0,0:17:30.85,0:17:31.69,Default,,0000,0000,0000,,low Reynold's number Dialogue: 0,0:17:31.69,0:17:32.68,Default,,0000,0000,0000,,this is true. Dialogue: 0,0:17:32.68,0:17:34.95,Default,,0000,0000,0000,,Turns out at high Reynold's number, this is true. Dialogue: 0,0:17:34.97,0:17:37.41,Default,,0000,0000,0000,,And this is the simplest experiment to show that. Dialogue: 0,0:17:37.41,0:17:40.53,Default,,0000,0000,0000,,So what this shows is that drag is proportional to area Dialogue: 0,0:17:40.53,0:17:42.90,Default,,0000,0000,0000,,so with the same velocity, Dialogue: 0,0:17:42.90,0:17:50.06,Default,,0000,0000,0000,,the extra weight is balanced by the extra drag force. Dialogue: 0,0:17:50.06,0:17:52.44,Default,,0000,0000,0000,,Exactly, four to one. Dialogue: 0,0:17:52.44,0:18:00.35,Default,,0000,0000,0000,,And what that shows now--the consequence--is that Dialogue: 0,0:18:02.92,0:18:07.66,Default,,0000,0000,0000,,I'm gonna replace the proportional with a twittle. Dialogue: 0,0:18:07.66,0:18:09.29,Default,,0000,0000,0000,,So it has an area in it, Dialogue: 0,0:18:09.29,0:18:12.06,Default,,0000,0000,0000,,so I'm gonna get something with the correct units in it. Dialogue: 0,0:18:12.06,0:18:13.99,Default,,0000,0000,0000,,So it has an area in it Dialogue: 0,0:18:13.99,0:18:16.44,Default,,0000,0000,0000,,and now you have left the play with Dialogue: 0,0:18:16.44,0:18:20.16,Default,,0000,0000,0000,,density, speed, and viscosity. Dialogue: 0,0:18:20.16,0:18:23.81,Default,,0000,0000,0000,,So now let's actually construct the drag force as a result of that. Dialogue: 0,0:18:23.81,0:18:27.50,Default,,0000,0000,0000,,So we know from the experiment, it's proportional to area. Dialogue: 0,0:18:28.39,0:18:29.76,Default,,0000,0000,0000,,And now among these, Dialogue: 0,0:18:29.76,0:18:34.15,Default,,0000,0000,0000,,so this here is the kinematic viscosity, Dialogue: 0,0:18:34.15,0:18:39.89,Default,,0000,0000,0000,,which is the one you may be more familiar with divided by row, the density. Dialogue: 0,0:18:39.89,0:18:44.21,Default,,0000,0000,0000,,So, we got to put some of these guys in, some of these guys in, Dialogue: 0,0:18:44.21,0:18:46.02,Default,,0000,0000,0000,,and some of these guys in. Dialogue: 0,0:18:46.02,0:18:49.09,Default,,0000,0000,0000,,And let the units come in as a force. Dialogue: 0,0:18:49.09,0:18:51.84,Default,,0000,0000,0000,,Well, one of them we can do right away. Dialogue: 0,0:18:51.84,0:18:57.00,Default,,0000,0000,0000,,There's how many powers of mass over on this side? Dialogue: 0,0:18:57.00,0:18:58.84,Default,,0000,0000,0000,,In a force, just one. Dialogue: 0,0:18:58.84,0:19:00.14,Default,,0000,0000,0000,,Right, and there's one here. Dialogue: 0,0:19:00.14,0:19:02.69,Default,,0000,0000,0000,,So we need to get one over on this side. Dialogue: 0,0:19:02.69,0:19:04.92,Default,,0000,0000,0000,,Now, among all these guys, which of them have mass in them? Dialogue: 0,0:19:05.02,0:19:07.60,Default,,0000,0000,0000,,Not this one, 'cause you divided them all out. Dialogue: 0,0:19:07.60,0:19:09.28,Default,,0000,0000,0000,,Not velocity, Dialogue: 0,0:19:09.28,0:19:10.98,Default,,0000,0000,0000,,only density. Dialogue: 0,0:19:10.98,0:19:12.10,Default,,0000,0000,0000,,And density is one power of mass, Dialogue: 0,0:19:12.10,0:19:15.56,Default,,0000,0000,0000,,so you have to put one density. Dialogue: 0,0:19:15.56,0:19:17.76,Default,,0000,0000,0000,,Question? Dialogue: 0,0:19:17.76,0:19:19.24,Default,,0000,0000,0000,,[indistinct question] Dialogue: 0,0:19:19.24,0:19:21.56,Default,,0000,0000,0000,,So this is a force. Dialogue: 0,0:19:21.56,0:19:22.60,Default,,0000,0000,0000,,Good question. Dialogue: 0,0:19:22.60,0:19:24.47,Default,,0000,0000,0000,,So drag is a force. Dialogue: 0,0:19:24.47,0:19:32.58,Default,,0000,0000,0000,,So this is just newtons or uh, mass legth per time square. Dialogue: 0,0:19:32.58,0:19:34.70,Default,,0000,0000,0000,,Does it help? Dialogue: 0,0:19:34.70,0:19:38.25,Default,,0000,0000,0000,,So it's just newtons. Dialogue: 0,0:19:38.25,0:19:41.72,Default,,0000,0000,0000,,In SI Newtons or in general, mass length per time squared. Dialogue: 0,0:19:41.72,0:19:46.22,Default,,0000,0000,0000,,So mass times an acceleration. Dialogue: 0,0:19:46.22,0:19:50.44,Default,,0000,0000,0000,,Okay, so now, we've matched the units of mass Dialogue: 0,0:19:50.44,0:19:54.43,Default,,0000,0000,0000,,and there's-- but we haven't matched the units of time yet. Dialogue: 0,0:19:54.43,0:19:56.16,Default,,0000,0000,0000,,So let's sort out the time. Dialogue: 0,0:19:56.16,0:19:58.52,Default,,0000,0000,0000,,There's no time here, there's not time there. Dialogue: 0,0:20:00.19,0:20:01.86,Default,,0000,0000,0000,,There's T to the minus 2 there. Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Well -- what can we do about that? Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,We have to match -- We have to throw in some v and some nu (viscosity) Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And the problem is we don't know how much Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,So the time doesn't helps us enough Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Turns out, to make the time and the length work Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,The simultaneous constraint Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,The only way we can do it is that Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Okay, making the same argument Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Just to get the masses to match, the legths to match and the times to match Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,This is the only way to do it Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,So you don't have any viscosity Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,So actually that's the simplest experiment I know Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,To show that the drag at high speed, most flows are actually high speed, Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,High Reynolds number Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Is independent from viscosity Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,So it's ro, A, v squared Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And that is a great result because it tells you a lot of stuff Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,About everyday flows and everyday life Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Like for example, why did people reduced speed Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Speed limit on the highway back in the 70's, Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,To conserve gas Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Well, on the highway Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,You're burning gasoline to fight drag Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,So if you reduce the speed Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,You reduce the drag, Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,You reduce the amount of gasoline Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,In particular, if reduce speed by 20%, Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,You reduce v squared by 40% Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Which reduces drag by 40% Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Decreased gas consumption by 40% Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,So you can these things right way, just by a simple formula Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Which is a imediate consequence of this experiment Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Now, turns out, this -- how do you get that to work? Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,This is the low Reynolds number limit Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,You can't deduce it from this experiment, but, if you know that this is true, you can make the same argument Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And figure out, how the drag force varies for low Reynolds number Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Okay, now let's just check wheter this formula here Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,That we deduced, works at all Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,So the folow up question is the following Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Which is that I have -- 1, 2, 3, 4 Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Here on this side, I have 4 small cones Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,They're all identical to this small cone Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,So 1 small cone, 2 small cones, 3 small cones, 4 small cones Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,So I'm gonna stack all 4 small cones, into a thick small cone Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And I'm gonna race it against one small cone Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,So the question is: what is the ratio of these guys' terminal speeds? Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,So let's call v4 and v1 Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,So, 4... Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Okay, so, what is the ratio of their terminal speeds? Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,1/4, 1/2, 1, 2 or 4? Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,So, talk to your neighboor for just a minute, we'll take a quick vote and we'll do the experiment Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Okay, so let's take a vote and then we'll do the experiment Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,1/4? Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Who votes for 1/4 ratio? Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Who votes for 1/2? Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,1? Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,2? Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,It's about 35... Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,4? Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Oh, 10 Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Okay, so, let's do the experiment Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,1, 2, 3, 4 of them Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Okay so now let me drop them like --- that Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Well it's kinda of hard to tell isn't it? Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,So that was actually not well designed experiment, right? Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Because you actually have to get it out of timer and decide wich one is going faster Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And measure how long it took Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,It would be nice if had a way that was just like the other experiment Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,What was nice about the other experiment is when I drop them, Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,You got the answer, by the fact that they hit simultaneously Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,So if we can make them hit simultaneously Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Then that would be nice, now what do I have to do to do that? Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Well I either have to -- Yeah -- I either have to switch their heights Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,4 to 1 or 2 to 1 Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,So, let's try 4 to 1 Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Okay -- [laughter] -- Is that sort of 4 to 1? Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,No? What do I have to do? Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,This guy got go down Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,This is where my depth perception really fails me Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,So I only have a monocular vision. I can see with both eyes, but I don't binocular fuse Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,So I can't tell depth Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,[Indistinguishable suggestion from aluminum] Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Oh that's true