 Let's see, now I'm just, oh, so just some of the general things. Who's got the textbook here just so I can hold one up? I don't bring mine because I got the giant version. There we go. That's the textbook we use. Show it to the camera. It's a good book. That's why I use it. I wouldn't use a book I didn't think was a good book. Not only do I think it good, it's the book MIT uses. So it gotta be a good book. MIT takes this almost as seriously as we do. They have to. They're charging seven times what we charge. So tell me who's smart and who's not. You guys are sitting here getting the same thing for one seventh of the price and everybody at RPI at MIT. So exact same stuff. Exact same stuff that we're covering that they covered. Anybody have any trouble getting the book? Okay. It comes in a couple different forms. You'll need at least this volume one for physics one and physics two and three. There is a big version that has actually I think volume two is physics two and three. I forget what because I don't teach those. But if you're going on in the physics you'll need at least the second volume. The third volume that I remember is something we don't teach here. So don't bother getting it. But you can't get them in the full format. It's also available as I understand it in an e-book if you prefer to do that. But that's entirely your business. You get it used. No trouble. More power to you. If it hasn't come yet. You just ordered it on eBay or something. It's just not here yet. No trouble. Just if it doesn't get here soon and buddy up with somebody else so you can at least stay on top of the homework. This class like all of my classes is run through the angel course management software that we have here. Has everybody gotten on angel before or do I need to go over that a bit? Who has not seen angel yet? Everybody has. Okay. If not or if you're having trouble with it later just come see me. When you log into angel it won't look exactly like this. My version of it is a professor. But all your classes will be listed over there and one of them is going to be our class here. It's the engineering physics engineering 105. In there I have a couple things that we're going to use in some detail. One of the things is resources. I'll use this a lot. First thing you'll want to see is under course documents the course outline. That's where I kind of lay out some of the rules how the grading is going to go. There's a whole lot of legal stuff I have to do in there for SUNY to make them happy so the SUNY policemen don't come after me. So some of it's kind of dry. But also in there my office hours, my contacts, any of that kind of stuff if you happen to be somewhere and you just don't have it on hand you need to send me an email you can do it that way. But you can also send email through angel and I'll get it. So that works as well. Most important to you most likely is the course schedule. It looks something like that. A couple things you need to pay attention to of course is all the stuff that's there. There's an awful lot in there. I can blow it up a little bit just so we can see. One of the things I used to use is this reading. This book, each of the sections, each of the chapters are fairly short so it's not a lot of reading. If you skim through this before you come to class, what I talk about is just going to go a lot smoother because you'll already be a little bit familiar with it. So in the morning, first cup of coffee just sitting and stomping through that see some of the terms that are coming up, see some of the diagrams that are already there. Any of that kind of stuff does make what goes in class a little bit smoother because you're just already a little bit more familiar with it. I'm repeating stuff in a way rather than giving you stuff brand new so that it's coming out of sometimes it seems like nowhere. So that's the topic. The sections that go with it, these are the homework problems. It seems like there's a lot, we start with a lot. They're pretty simple ones to start with. They're very short ones to start with and then we start getting a little bit more complicated problems so you notice that there's fewer and fewer. Don't forget too though that we only have class twice a week. You don't have to have these ones done for the next session. But if you leave them all to the end, you've got way too much work to do to get the homework in on time because each homework section is due at a certain time. So this first one's due in a week. The second one due, then after that notice there's two days in that and so on like that. The homework is the same thing to you that practices to an athlete. It's a chance for you to go through some things, make some mistakes when it's still cheap to make them before you make them in the big game which are the tests and the like. So do the homework. I collect it, I look through it, I don't grade it in any detail. I'm not looking at your specific solutions in the homework. I'm going to give you the full solutions and so it's your job to sit down and see what the solutions to the problems are after you've already worked them out. I'll grade them almost entirely for format to see how you laid out the problem. Did you communicate to me well that you had a feeling of what you were doing? You were making some effort at it? I look very, very little at the actual specific contact of these things which means you can still do them wrong and get full credit for it. So it's worth doing the homework. I'll grade them on a ten point basis and if you've done all the problems and you've made a real good effort at them and that means that you wrote complete sentences, it's legible, your drawings are nice, all those kind of things, I'll give you the full ten points even if your answers are wrong. If you don't do anything, you get a zero and then of course there's a whole smear of stuff in between. I will accept homework late. You can come into the final exam and hand me Homer and I will accept it and grade it. It's only half price by then but that's better than a zero. And I'll have put the full solutions up by then anyway so all you have to do is copy them and you'll still get at least five points. That's a good deal. That's how important I think these problems are to go through that I'll even give you five points for doing them by copying them from me. That's a pretty good deal. There shouldn't be any zeros on the homework, that's for sure. We'll also have occasional chapter exams. It doesn't show up quite there. It shows up a little bit later when we get them. They're on the schedule. Most of them I think all of them but now all three of the chapter exams will be done during lab session. That's what these last three columns are. What we do in the Tuesday lab. The activity we've got. What we're going to do. What I expect you to turn into me and when. And we'll talk about that in a lot more detail as we go through it. And then the exams we will do in the lab class itself. Not because it's a three hour test. It isn't. It's a one hour test maybe. But you've got three hours if you need it. And a few of you here will take the three hours. In fact we'll probably go to four and a half or five if I like you. But I have a life of my own. So I'll give you the boot after a little while. Most of you though will be out and gone an hour, hour and a half. Just take the three hours because we've got it and I want you to relax the tests. It's a necessary evil. There's thousands of research papers on how terrible it is to give tests and nobody's come up with something that's a lot better. At least not in this type of class. So we'll do them. But I would like the pressure to be off of you. They're open book, open notes. I'm not going to check to see what you brought in with you if you want to bring in three textbooks. No sweat. The only thing you can't bring in is this old trick where you put a piece of paper on the floor and then have a graduate student in physics stand in and say that's what I brought in on a sheet of paper. Now it will fall for that trick. You've seen it. So you can't email anybody. You can't text anybody. But open book, open notes. I don't care. If you want to photocopy all this homework solutions and bring them in, I don't care. I want you to relax and do your best on these tests. It's my best interest if you all got an A. You won't all because some of you will fight me to the nail for your right to get a lower grade and you'll win. But I don't want you to have anxiety for the test. Just do your best. That's all I want to see what you're gathering from what we're doing in here. Any questions so far? Oh, one other thing you need to watch on this is up in the upper corner is a date. That's the last date that I modified this. So if that changes, then somewhere on here I modified things for whatever reason. Maybe a snow day or a sick day. Sometimes I just decide to change things up as we're going through it. So that date will change. I may not mention it in class. I might forget. Or maybe so minor that I just don't happen to bring it up. If I do make changes, I will say what they are in yellow. That's what it says right there. So that if I just change a problem number to I'll highlight it in yellow. You don't need to print it out again. You can just mark it on your sheet and you're all set. You don't have to make another print. But keep an eye on that. I'll try to mention it if I make any changes. Sometimes it's going to be obvious I make changes. If we have a snow day, obviously I've got to make changes to that and I'll make them usually by the next class period. So I probably won't mention that that just makes sense. All right. A little bit, well I'll talk more about the lab business when we get to it tomorrow. What the tents are there for us to do. So that's the schedule. You can get to it by golly right from there. The course schedule. Print that out. Keep it with you. Refer to it. That's where everything you need to know about the details of the class on it. Also here's the homework problem format. Just a little thing I wrote up, explained, gives an example. It took a sample problem and said here's how I would do that problem if I were you if I wanted all the points available. I also though, later on, show what you can do to get fewer and fewer and fewer points as we go through until you can get down to the bottom. Here you've got one point if you just do that. Just turn in something that's non-blank and I'll give you a point. Also there, it'll be more used to us starting tomorrow are what I call lab links. There's the first lab we're going to do so you can read about that when you come in. I'll have copies available for you tomorrow so you don't have to print them out. All the labs, all the lab instructions and the like I'll always put on there. Usually not the day before but if you ever misplace them or need to look at them again you'll always have a copy available to you. Useful links, we're going to be using Excel a lot because we're going to take a lot of data. That data then needs to be digested, manipulated, reduced. One of the major things you'd ever do in a lab is how many students here are engineering students and the rest are science, chemistry, physics, undeclared. A lot of you will get into a lab or a field situation at some time anyway. It's called data reduction because you're going to take a whole bunch of numbers in a lab but then what you turn into your boss is reduced down to maybe just a single number. One of the best ways to do all that is with a spreadsheet like Excel. So we're going to be doing a lot with Excel. Plus we're going to be doing a lot of graphing of data in this class. It's a terrifically powerful and simple tool to be able to graph something to visually see what it looks like. It's tremendously important. We'll work on it a lot. I'll drive you nuts, even nuts are than usual over this type of thing. So if you don't know how to use Excel, we're going to learn a lot of that. Let me know if you have no experience with Excel so I can help you right from the start. There's 10 or 12 things of Excel that we really need to know how to do. So that doesn't take long to pick up. But you've got to let me know if you need help with it. A whole paper I've written on graphing and how to make graphs. They're that important. When I was working for General Electric, my boss gave me something to do. I made a graph, gave it to him. Then about six months later, I went to a meeting with people I'd never met before. The guy was giving a presentation in the meeting on some work they'd done and up comes my graph. I had no idea they even knew who I was. They probably didn't know who I was. They probably had no idea I was sitting there and they'd never met me. It's just that my work went to my boss, went to his boss, went back down to somebody else and a different component of the company and they needed what I'd done on that graph to put up. When I saw that graph come up on there, I said, thank God I did a good job on that graph so I didn't look stupid. And ever since then, I've taken this graphing business really seriously because I don't want you to look stupid. Some of you are going to try your best to do that. And I'll try my best to stop you from doing it. Again, too many times you'll win. But I'll try to stop you from looking stupid. Graphing's a big way to do it. Plus, who in here really loves to write? Just loves writing. Could write. Some of you, some people do. Most of us don't like writing. Pictures worth a thousand words. You do a good picture. You just save yourself a thousand words. That's a good deal. That's a great exchange rate. So do a good thousand words in a nice picture. Then I have this whole section on writing technical reports that will go through lots of links on there of good things I found over the years that you can use. Banning's ten commandments. Violate these and don't bother turning anything in. The lab work is about a quarter of your grade. If you want to throw that quarter of the grade away, here's the way to throw it away. Just don't even read that. Just ignore what I put on it. We'll talk about this a lot more as we go through. But start getting ready for this. I'm hoping in the end that one of the things I can get across to you is that the written presentation of the work you do is tremendously important to your success. You can be the best engineer or scientist in the world, but if the stuff never gets off your desk, what good is it to anybody? You cure cancer, but it never leaves your desk or you can write it up so poorly that nobody even recognizes that you did. So what? What good is it to anybody? So you've got to learn how to write things, present things, to share things in a technical way with somebody else. Part of that you want to look at this way is I speak a language that you're going to learn how to speak. No different than if you were learning Spanish from me. You need to learn how to communicate with those of us who are already out here because it's those of us who are already out here. Well, I'm going to decide how many points you get. After this, somebody's going to decide how much money you get. You want to impress those people, don't you? You want more points from me and more money from them and this is going to help. The better you write, the better someone's going to think of you, they're going to be worth it to the company and the more they'll pay it for that. That's a simple reality. I'm not making this up, this isn't hyperbolic. That's the way it is. If you're worth it to the company, they'll pay it for it. Also, that will show up here, there's nothing there yet because I'll put the full homework solutions here. That'll come under course resources. I'll have homework solutions. You can click on them by number and they'll come up. With all of my solutions, every exam I'll completely solve for you and put up there the day after the exam unless somebody still needs to take a stone and miss class. All that will be available there for you. I try to make as much available to you as I possibly can. Just nothing else so you don't bug me later. You can be a great job if you want for the students. I'm trying to get rid of the students, but they'll come away from me. That's my plan. Also, discussion forums. If you have... Look at my spelling there. I got a new keyboard. I'm not sure all the keys work. Maybe my fingers are getting fatter as I age. If you have a question on homework, post it there. Don't do what the morning the homeworks do because you may not get an answer in time. But if you're four days ahead, post a question in there on the homework. I'll post right there any corrections or hints. If I find out a particular problem is given to everybody some trouble, I'll post a hint there to let everybody be able to solve it. If somebody posts a question there and you can answer it, answer it. You give a good answer, I'll give you extra credit points. Why not? You've done some work for me. I'll pay you for it. I'm pretty generous with extra credit. Four or five hundred thousand extra credit points of the shot. I've given some students so many extra credit points they took them and cashed them in for a PhD and they're out of here. That's pretty good. That's a good deal. Get your PhD in a couple weeks here and be gone. Where do you think I got mine? Well, I got mine on eBay. But all that kind of stuff will be available there. Anything I think that can help you will be there. I'll put up on here. And if there's something you'd like, if it's not there, ask me for it. I'll put it up. Also, of interest to you are grades. As we accumulate some scores, I'll put them on Angel so you know what I've got in the book. If you've got a 30 on something and I accidentally recorded a three, you want that fixed, I think. I presume. This is the only way you and I are both going to know what went into the grade book and if I entered something wrong. By the end of the term, I'm going to have to put in, I got this class, I got four other classes. By the end of the term, I'm going to have to put in 400 numbers. I'm going to make a mistake on at least one of them. I don't want it to be yours. This is the way to check. One thing I warn you about though is Angel will calculate a percentage grade for you. I cannot for the life of me figure out how it makes that calculation because it's always wrong. So, don't look at the percentage grade. It gives you a total percentage of all the things that are to do. I think what it does is I go into Angel and I put in the four categories. Homework, chapter exams, final exams, and lab work. I put in those four categories and if you don't have any scores for the final exam, for example, which you won't until the last day, it gives you a zero for that and then figures it into the calculation. It doesn't make any sense. I think that's what it does. But I don't care to look into any part of this. Ignore the percentage. Just make sure the numbers are all right. If something's wrong, bring the paper to me. Say C, you crook, you gave me a 30. You want to put down a three. Say it nicer than that. You're asking me for a favor. It's a good favor. You deserve it. But be nice. All right, so check the grades there as they go in. What else? There will be a final exam. The time is already on the schedule there. The schedule I just had up. There's no reason to miss that. We've got lab as we go along. Chapter exams, homework, that's pretty much everything. Cell phone policy. I have cell phone, very strict cell phone policy for my classes. I understand that you're the wired generation. You couldn't possibly conceive of not being in contact with the homies at every minute. So you want to leave your cell phone down. I understand that. And so my policy is you leave your cell phone on if you want to. I have no trouble with that because I know you want to be in contact with everybody at every minute. That's what you're used to. That's what your life has been since cell phones came out. When you're in fourth grade or something, probably. So leave your cell phone on, no trouble at all. I don't have any trouble. Any other professors say that as their policy? I bet you not. I bet you haven't heard that today. However, here's the deal. You leave your cell phone on, no trouble. If it goes off and distracts me, I answer it. No questions asked. If it goes off, you hand it to me and I answer it. If it's your girlfriend, she will not be by the end of that call. If it's your mom, I will know exactly what you left on your bedroom floor that day. If it's your stock broker, I'm going to sell everything in your portfolio at the market. And I will probably short the other half. Go look that up and see what it means. You're going to be in trouble. That's the deal. Leave your cell phone on. I have no sweat. No trouble with it. I don't mind it all. But I answer if it goes off. That includes a text, which is usually some stupid little noise, but I'll know who it is at that moment. So I'll know whose phone has got a text message and I get to answer it. And I have trained in the use of every cell phone there is. So don't think I can't figure out how to send a really good text message with all kinds of explanatory graphical language of some kind. Deal if you want to sit in class and text and it doesn't bother me, go ahead and do that. If it doesn't you know I care. So go ahead and if you want to text just don't distract me. If it bings or dings or rings, that distracts me and I get to answer it. But if you're just twilling away under the desk, because I know some of you can, we got two women in here, they can text, God man, women, they can text like crazy. I know that already. I have a daughter. You don't even have to look. Are you one of those? You can text under the desk? No? You're not that good yet? You're working on it? If you can do that I don't care. Studies have shown if you text a lot in class you do as well as someone who never comes to class at all. If you text in class a lot you might as well not even come and save the time. And it's not going to hurt you one bit. That's a pretty good deal too. If you're a heavy textor, take the day off. It's not going to hurt you. You're still going to fail. All right. Deal on that. Understand the cell phone policy? Okay. Any questions? Concerns? Accusations? Nope. We're okay? Everybody, we're all right? All right. Let's get down to that which we call Physics 1. Make sure I got everything here. For the most part I did. Physics 1 is often generally called Classical Mechanics. What we're going to worry about in this first part of Physics is the simple idea of where things are when are they there what are they doing next how do we make sure they do next what we want them to do or prevent them from doing next what we want them to do that's the simple type of stuff we're going to look at in this Physics 1. It has an awful lot to do with the type of things you do every day. None of this is going to be completely out of the realm of your experience. This is all very real to life stuff. Some of it is going to be simplified a little bit. There's things that you're just not ready to study yet the reality of the way things work is just too complex. The mathematics is too complex. Some of the concepts are too complex. You're just not there yet hopefully you will be and if you don't need to be then you won't go that far and you'll be fine for it but we're going to start out with some very straightforward things that you're very experienced with yourselves as regular everyday people in a physical world will drill down in some more detail in some of it than you would just walking around but a lot of it has to do with just how in the world you get from one place to another during your day. There's things we're going to cover in here that might save your life. I can guarantee we're going to talk about a couple of those things I know they've saved my life more. I don't know if that's good news to you or bad but it's certainly good news to you if you save your life so we'll cover some more of this stuff in some good detail as we go through here alright physics like any other physical science is very very much a science of measurement. We can't do any of the things we need to do in physics or science or chemistry or engineering if we can't measure some things and once we measure those things we need to relate those measurements to people in a way that they understand so one of the most important things that we in the science community have come up with is the system of units that we use. We will use most part the metric system what's also known as the SI system actually that's kind of redundant called the SI system because that's what the S stands for system international it's the metric system you've all heard of it you've all been used to it it's made up of only three fundamental units one unit is that which we use to measure the length in the metric system that fundamental unit is the meter anybody know how the meter was defined how do we know what one meter is because it's finally important if I call something one meter and I'm working with some people in India as so much of the engineering is done nowadays half of the Boeing corporation is in India if they don't know what a meter is that I'm thinking how are we going to build a plane that's going to fly we've got to agree on what a meter is so and some time or other it wasn't all that long ago the meter was defined by the metric system some bureaucrats how did they define a meter anybody know it is now it's that kind of thing now because it's much more precise it's well when you hear how it was originally defined you'll realize we needed something else so now they define it as so many wavelengths of a vibrating and a Armenian atom or something I don't know what you can look it up if you need to know but it is that kind of thing but that's not how it was originally defined that's how it was defined and quantified now so that you know what a meter is and the guys in India also know what a meter is so we're going to build something to the same size when we're working together but then we know how the meter was originally defined because this was like the 1870s or something they said this will actually they said it in French because the French is how we'll do it pretty awesome French accent the girls are there anybody speaking of French accent it's just amazing isn't it British seems if you want to have your own TV show you have to be British nowadays anyways so in the 1870s 1880s or something a couple of French guys sat down and said this is a meter nobody knows well it had to be reference to something everybody's got so that there wasn't I couldn't say a meter is this length of wood I have in my backyard because nobody in the other countries got that it's got to be something everybody's got right no because everybody's got a leg but not everybody's got the same length leg I don't know if you knew that or not you probably thought they're all standard issue what's one thing everybody in the world has how do we make icicles everybody in the world we all share one thing we share so that was the basis of the reference for the meter the equator to the north pole divided into it's going to take me a while to draw all these divisions divided into ten million pieces divide that distance from the equator to the north pole into ten million that length of one piece is a meter that's how it was to find we're going to double check this in lab tomorrow you think I can't measure ten million things I'm going to give you a two meter stick so you only have to do five million everybody in the world has the world at their disposal so one quarter of an arc length around the world divided into ten million parts was called the meter so now you can see why that's a good start because everybody's got the world to refer to but it's not all that practical so they redefined it as so many wavelengths of a certain atom and vibration emitting light or something like that you can look it up it's all there but at least it was a standard reference that we could all agree on that was a big in fact that's part of what inaugurated the industrial revolutions now we could communicate with each other on what we were doing in the English system there's the foot how do you think that unit was first defined it couldn't possibly be something so stupid as the length of somebody's foot could it it's exactly what it was it was the length of somebody's foot it was the king's foot what do you think happened when that king died and a new king came in what happened to the measuring system what happened to the whole system of commerce when the basic unit of measurement changed everybody out in the countryside knows that the king died but they know the size of the new king's foot that's the English system that's the kind of thing it's based on it's tremendously colorful it makes a great story but god how do you do engineering with that kind of thing it's very very difficult yeah that foot's standardized now there's a bureau of weights and measures that agrees is now but back then it was terrible and the hard part too is the continuing hard part with the English system is everything all the subunits of the foot were defined some other way if a meter is too long for us well we'll just use centimeters or millimeters but it's no trouble because we know exactly what that definition is it's just multiples of ten but if we don't want to use feet we gotta go down to inches how was the inch defined it was not defined as one-twelfth of the king's foot what they found is they defined an inch here and they defined a foot there and about twelve of them fit in so they said I'll let's just call it twelve but how was the inch originally defined because they had an inch word no that's how the inch word was defined all the inch words are one inch the inch was originally and I'm not making this up God I wish I was I'm not making this up the inch was three barley corns laid down end to end that was an inch three barley corns what are the chances that the three barley corns you carry with you every day are the same size as the three barley corns I carry every day and happen to be the twelve of those were about a foot so they said look we gotta stop with the king's foot we gotta stop with the barley corns and stuff so now they tried to define them better but the trouble still is if we don't want feet we gotta go down to inches we gotta remember that that's twelve then the inch is that divided into quarters and eights and sixteen and everything it gets just a mess and it gets it doesn't even stop there it goes farther and farther and farther but those two things will be our fundamental units for length we'll do some stuff in centimeters and millimeters and kilometers if it makes more sense we'll do some stuff in miles or inches if it makes more sense but basically that's where we'll start with meters and feet the next fundamental unit was that unit that measures mass mass is is how much material is there in something and we figure out what it is by exerting a force on that something seeing how fast it accelerates and from that we get the mass sounds kinda complicated but we'll make a little bit more sense of it later the basic unit in the English system for the mass is the kilogram anybody know where that came from? how they first defined the kilogram now remember the whole basis of the metric system is something everybody can use to agree on not the mass of the king's head or his 20 of his coins in a burlap sack or whatever I don't know what Alan? there you go water everybody's got water so that's how they did it look the length they'd already defined and they said let's take one tenth of a meter we'll make a cube a tenth of a meter on a side which is how many centimeters? is a tenth of a meter? there's a meter how many centimeters in a meter? a hundred, centen is what it means, centen means a hundred so we got a tenth of that ten centimeters so this is a little cube ten centimeters that's a volume that volume in fact that's a liter a liter of water has a mass of one kilogram that's how it's defined pure water distilled because you don't want some of the pond water you guys have been drinking out of when you were little kids in your formative years which explains a whole lot about your personality so everybody can come up with ten centimeters on an edge of pure water and now they know what a kilogram is actually in France in the office that takes care of all this stuff is a kilogram mass of I don't know it's palladium or some extremely rare metal that's extremely stable that it doesn't change much the heat and it doesn't wear out as people handle it and it's about seven floors down through bolted doors in this building and you've got a if you want to check your kilogram against their kilogram which everybody in the world has to do every once in a while to make sure we all have the same kilogram you have to send your kilogram out to them and they'll weigh it against your their kilogram reference against yours they might shave a little bit off yours or maybe put some bubble gum on if they need some more they'll make it so they balance then they'll cash your $40,000 check and send it back to you but they will not let you come in and touch that thing it's that vitally important that everybody agrees on these units the kilograms and the like it's that important so a kilogram of water about that big you've got an idea about that so now you know about the mass of a kilogram the unit of mass the English system there isn't a good one there's two that are in some use they're both kind of stupid we're not going to use either one in this class because they're both kind of stupid and it's not my job here to make you stupider if I can help it and then the remember I said there are three fundamental units after that everything else is defined from those three the last is time and it's the one thing that both the English and the SI system agree on the second is our basic unit but we will use hours we will use days we will use years and like this one was it's the only one in the SI system that's kind of built on on the story of the human existence like the king's foot was a day was pretty easy for everybody to define you know basically how long one day is then they divided that into 24 divided in 24 because that's fairly easy to divide remember when they were making instruments they had to eyeball or measure a lot of division so it was fairly easy to divide something into 12 segments and then I don't know why they did it in an hour then into 60 and a minute 60 of those is the second I don't know why it's 60 why not something else we'll use those basic ones every other thing we measure from here on out will be based on these three and we'll get to them we'll talk about them as we get through them oh I do that let's see that I haven't written down here but I actually checked my notes I can see the meter one meter is defined as the distance light travels the distance the distance light travels in one two hundred ninety nine thousand seven hundred ninety two two hundred ninety nine millions seven hundred ninety two thousand four hundred fifty eights of a second light goes that far so all you have to do is have a stopwatch however time had to be also defined it's nine billion one hundred ninety two million six hundred seventy vibrations of a cesium atom which of course everybody carries in their wallet so they can check that alright everything all the units from then on will be derived units that we'll get to as we talk about them as they come up alright one of the most important things you can do with those good thing that one of yourself won't know what I answered it one of the most important things you need to learn to do with these units is pay attention to them if you give me an answer and you don't tell me what the units are on the answer you tell me a certain length but you don't tell me if it's meters or feet you're not getting credit from me because I don't know if you're right or wrong if you haven't told me it's seven meters how am I going to know it's not seven feet I'm not giving you credit because swing in the dark I'll give you credit for a good answer so every answer you give me has got to have the units with it or you will not get full credit from me I guarantee you that right now and that's not negotiable you can't come to me and say I want my points back here's what I meant here's where I was somewhere else on the page it's not my business to go looking for your answers it's your business to give them to me so every answer you've got has got to have the units with it if you don't think that's important then imagine when you go get your first big job you get through the interview process some big engineering firm makes an offer to you and say yeah we're going to pay you 80,000 a year you're going yes 80,000 a year and by that red car I've had my eye on for so long that's all guys ever buy with their first paycheck a red sports car 80,000 and you go to pick up your first paycheck and it comes and it's very small it was 80,000 pennies a year I didn't ask I should have asked them was it 80,000 dollars a year or 80,000 pennies a year I didn't ask units matter on these numbers I even had see I've tried this already in class today and it's flopped terribly because you guys are also culturally naive which means you don't know things about the world that I know anybody know what Perry Home Companion is you do? one person nobody else knows but Perry Home it's a radio show very funny radio show it's on every Saturday night oh the trouble is it's on NPR don't know where NPR is do you you do because we're cool we're sophisticated you guys you're just on your cell phone all the time in your red sports car a units joke on Perry Home Companion this weekend I thought oh I wish my students that's a very funny units joke a guy who went to the doctor he wasn't feeling good doctor I don't feel so good doctor did some tests came back to him and said bad news I think you're going to be with us about 10 more 10 more years months days the doctor said 5 4 3 2 3 4 3 4 3 4 3 4 3 4 3 4 3 4 3 4 3 4 3 4 3 4 3 4 3 4 3 4 3 4 3 4 3 4 3 4 3 4 3 4 3 4 3 4 3 4 3 4 3 4 3 4 3 4 3 4 time by looking at the units we figured out how to calculate speed it's the distance traveled divided by the time it took to travel that distance well you knew that anyway it's 150 miles to New York City you did it in 3 hours what was your speed 150 miles in 3 hours your speed was 50 miles per hour you can if you forget how to calculate something figure it out from the units I remember freshman year doing this in a test I couldn't remember how to figure out something we weren't in the enlightened days of open books, open notes tests I couldn't remember the equation I needed I looked at the units and figured out the equation what it had to be for the units to work out so you can use it to come up with things you don't know about yet everybody knows about speed but that was just a simple one we could pull off real quick here the most important way you need to use dimensional analysis is to make sure they match when they have to match here's an equation that you may recognize from high school physics if you took it across into a couple weeks here actually a couple days delta x equals 1 half at squared plus v i t we'll leave it at that now maybe you recognize this maybe you don't, it doesn't matter we'll get to it as we go in the details, but what I want to demonstrate is this business of dimensional analysis is very important and how very easy it is to do you don't know what the delta symbol is yet we'll get to that but x is a distance so we might measure x in meters the delta means change in so this is change in x, change in if we're measuring something in meters and it changes, it's still going to be in meters so we know this should be in meters then there's an equal sign so if those things truly are equal if it's meters on this side it darn well better be meters on that side or I don't know how they're going to be equal I don't know how something in meters can be equal to something not in meters so this must be in meters as well 1 half, well that doesn't have any units on it, we'll see where that 1 half comes from a little bit later a, what do you think a stands for anybody remember from high school physics? acceleration you might not remember what the units are in acceleration so fine, leave it at that some of you remember what those units are some of you don't what are the units on time though? seconds oh, but we're squaring it so this will be times squared that's all that can happen when you square time well the only way meters can equal something times second squared is if that something has units of per second squared that way the second squared will cancel we have meters equals meters and you just what the units are on acceleration who remember that acceleration comes in meters per second squared I was right, wasn't I? acceleration has got to be in meters per second squared for this side to equal that side so if you ever forget what the units are in something take a second figure it out also, double check a lot of times you're going to be writing out an equation maybe you can't remember is this squared or isn't it I can't remember if that should be squared well this tells you it's got to be squared because it wouldn't work out otherwise that'll help catch those little types of mistakes so two things on either side of the equal sign must have the same units which you'll only know if you analyze the dimensions dimensions and units kind of interchangeable terms this side oh gosh I just can't remember what the units are for v but I know already the units for t are seconds so units for v have got to be meters per second same thing we figured out there well that was miles per hour this is meters per second still it's just a velocity once again meters equals meters plus meters you can't add or subtract things that aren't of the same units you just can't do it it's not a rule I make up because I'm an annually retentive engineer yeah I know that's redundant it's not a rule that's just the way of the world you can't add things together if they're not measured in the same way and they can't equal each other if they're not measured in the same way and of course subtraction and addition are really the same basic operation so you can't subtract things that aren't the same units either so analyze the dimensions, the units on your problems and you'll save yourself a ton of points if you ignore those you do so at your own peril don't come winding to me and I only left off my units it hardly means anything anybody remember about about five years ago you probably don't remember anything five years ago you're only that tall about five years ago we were sending up one of those exploratory probes to Mars and I don't know if you've ever seen the TV show where they're in the command center as these probes are going to land on Mars and all the engineers are crowded around the computer monitors and the TV screens because all the work of years and years and years of incredible labor to produce this probe that is now millions of miles away and about to land on a different planet it's all coming down at this one moment so they're all gathered around they all have matching t-shirts with their boss bot form and you can see in the background there's cake and there's punch and everybody's all excited and they're all looking at these monitors this probe is about to land on Mars and the first signals will start coming back from Mars and they're all nervous and there's a little blackout period while it goes through the atmosphere and all kinds of exciting it's very dramatic but we like that kind of stuff and so they're all crowded and they're looking at the monitors and they go into the blackout period which means that the probe is just enters the Martian atmosphere there's not a lot of atmosphere there but there's some and so there's that incredible heating up that happens and it cuts off communications and then a couple seconds later it's supposed to come back out of that and they get the signal and then they know just where they are and it lands on the planet and then the the solar arrays pop out and the antennas go up and the guy driving the thing wakes up and all the signals start coming the probe went into the atmosphere, the signal disappeared signals do back and I don't know what 12 seconds but 15 seconds goes by then 20 seconds goes by 2 minutes goes by can you imagine the sick feeling of those people that just put their heart and soul into this project for 5 years can you imagine the feeling of the principal investigator the person who got the millions of dollars to pay for this it was his idea and it's gone and they never ever ever got a signal from that Martian probe they have no idea to this day where it is it disappeared completely but they figured out they figured out why they lost it they just don't know where it went and they can't go get it back they figured out why they lost it it happened because you'll find out most of you when you go to work in an engineering firm especially a big project a big project nobody works on an entire object everybody works on little parts of a thing and then they communicate with each other to make those things all work together one group was working on one part of this Martian probe and some of their information related to how somebody else's part was working on this Martian probe but they didn't use the same units on their measurements some of the numbers this group was using was 7 meters this group was using a millimeter something I don't know what the details were but they didn't communicate the units with each other so the things didn't work together like they were supposed to they didn't check their units something as simple as this and that Martian probe and all of those man hours and all those millions if not billions of dollars is gone so I bet you we're several engineering careers so it's terribly important at times now we're not going to kill anybody in here I hope we might get to that but we'll stop before we go too far but learn how to do this now so that later when your career is in jeopardy with every single thing you do as it will be because if you were an employer and you treat your employees you wouldn't say it to their face but that's the deal you screw something up in the company you could lose your job and it can happen like that not here not positive it happens like that so let's learn how to do it now so when your career is in jeopardy at least it won't be in jeopardy with that because that's such a simple thing to do hey put that thing at 10,000 okay 10,000 it is not only later it goes at millimeters or centimeters about 20 years ago an airliner was flying into Canada who was flying across Canada they had they were only about halfway across Canada they looked down and they're out of fuel luckily the pilot was kind of like that guy who landed in the huts he knew what he was doing behind a plane that's not working right and he was able to land the plane because it ran out of fuel halfway through the flight why didn't they fill up the tanks when they left so they had enough fuel to get all the way across Canada well they thought they did the way they fuel up planes it's something like they weigh it then they pour in some fuel again it's something like they don't weigh the plane they weigh the tanker that's doing it they do it by how much weight of fuel is going over and they had the wrong units because one person thought it was pounds the other person thought it was kilograms or something like that so they only put in half the fuel that they needed and luckily the plane didn't crash because the pilot was able to land it but it was because the travelers didn't check the units on the measurement they didn't put in enough fuel so don't do that either be careful with this did I get that point across at all I say that because I don't know how many of you will turn stuff into me without the units or with wrong units or units you just ignored here but I don't have it well I'll just throw in the squared I'll just put it on your career's in jeopardy because you've got to get through this class if you want to be an engineer or go on to the other things you might want to do if it's not engineering so one thing we're going to have to do is occasionally we have numbers that are in certain units and they're not the right ones but maybe we need that measurement to be in meters and we have to know how to convert it then so it's a vitally important skill to learn how to convert units we can convert similar units to other similar units we can convert length units to other length units we can't convert length units to mass units you're doing something entirely different this is about converting units measuring one thing into units measuring the same thing just with a different scale same thing you do is if you put down a meter stick went over and got a ruler and put down a foot stick an inch stick a ruler so we got to learn how to convert units a couple things make this very very easy one of the things is that what happens when you multiply a number by one what happens to it pull your calculator out and check if you're not sure when you multiply by one you don't change the number that's really important to us this unit we don't want to change the quality of what we're talking about just the way we're talking about it so we can multiply by one all day long and we're not going to screw anything up that's the first thing you need to remember about multiplying converting units the second thing you have to remember is well one you're going to multiply by there's lots of ones out there I don't know maybe that doesn't seem like it makes sense because you can probably only think of one one a equals a then what's a over a equal I didn't even tell you what a is I don't need to do I you know that that's equal to one so there is the one you're going to multiply by right there I wouldn't think so because you still don't know what a is alright here's the deal let's do something real simple let's say we have a measurement that's 6.7 feet and I'm going to do it in the English system just because everybody's so used to this that it won't be any strong most of you have used the metric system some but you're just not all that comfortable I myself I've been in science and engineering I still don't think in the metric system you want to ask me how far this my house I'll tell you in miles you ask me what temperature is well I can't count that low but tomorrow when it's warmer you want to ask me what the temperature is I'll think in degrees Fahrenheit not celsius I just don't think that way neither do you we're Americans we can't handle that kind of stuff like the old lady said I can't start measuring gasoline in liters because I can't afford to get a new gas tank in the car I have to measure in gallons that's what my car holds in old liters poor old lady just imagine her under a porch in a rocking chair with a 22 on her lap shooting the kids as they go on her lawn poor thing 6.7 feet into however many inches that's what I talk about when I talk about a unit conversion we've got something in feet we want it in inches instead now most of you know there's 12 inches in a foot but maybe some of you are thinking do I divide by 12 or do I can't remember you don't need to remember we'll let the units tell us what we do when we divide the units will tell us perfectly how to do it what we have to do is figure out we've got that we want to multiply it by 1 but we have to figure out what the 1 is we want to multiply it by so we need something that says a equals a that relates feet to inches one foot equals 12 inches there's our a equals a there's our a equals a now what I have to do is I don't multiply by this because that's not one I want to multiply by one so I want to put one of these over the other the question is which because it's just as true that that equals one as it is true that that equals one which one of those do I use don't worry about it let the units tell you what we're going to multiply this by a over a I have feet here that I want to cancel because I don't want feet, I want inches I want to get rid of this feet so one way to do that is to divide by feet then I have feet divided by feet and they cancel the magic chalk of translation comes out to prove it feet cancels feet so I know I want the one where the feet are on the bottom and the 12 inches is on the top I don't have to remember do I divide do I multiply by 12 that'll tell me maybe you had in your mind anyway but I'll I guarantee you half of you in here if well we'll do in a second we'll change yourself in a second 12 times 6.7 huh 80.4 there we go I have to remember do I divide by 12 or do I multiply by 12 there's only one way it's going to work out with the units you have to multiply by 12 so the units will work out you don't have to memorize anything alright maybe you had that one in your brain anyway you knew that you and Lisa multiplied but if we go to the metric system a lot of you have more trouble with that so let's say we've got something that's 801 millimeters and I want to convert that to meters now most of you know well we're going to have to divide or maybe multiply by I don't know it's metric system it's 10 or it's 100 or it's 1000 or it's 110 or 100 or something like that I can't remember let's not worry about it let's let the units tell us what to do remember what Millie stands for some stuff you do just plain and simply have to memorize you've got to get used to this stuff Millie is 1000 so the a equals a we're looking for that one millimeter equals one 1000 of a meter you can also do it as well if I take out the first M I can just put in 10 to the minus third and we've got it there I have millimeters on the top so I want millimeters on the bottom now I'm just trying to figure out what the a over a is that I want to do so there's my a over a millimeters cancel I'm left with meters be careful that this meter doesn't go down here on the bottom it's just one 10,000 time that that tells me that I take 801 divided by 1000 and I get meters I don't have to remember do I multiply by 1000 do I divide by 1000 I can't remember and you're all done you've had trouble do I multiply 1000s I bet you have I have who hasn't if that's not the way you wanted to see this you could have looked at it as 1000 millimeters equals one meter there's your a equals a you get the same answer it still comes out to be the same thing and this is where some students get trapped so pay attention carefully this isn't the first homework and we're going to do it a ton of times in class you're going to do it a lot more in your career what if we're not working with something simple like length but we're working with something that comes from length like volume say we've got 62 cubic centimeters we're working with in a problem I give myself some space because I know I'm going to have to multiply by a over a let's say I want to get that to inches but I'm going to do it instead for whatever reason you're working on design you did design centimeters you need to buy some stuff but when you go to the vendor they don't measure in centimeters they measure in inches so you got to order in their units because they're not as smart as you are so you want to make them do a conversion and not trust them to do it or trust them to not do it so we need to measure by what we happen to know offhand how many inches cubed in a centimeter cubed anybody know that offhand no looking anything up you know inches cubed converted to centimeters cubed that's not what I asked is it you've always had this trouble Alan you answer what I ask I didn't ask but I asked about cubed anybody know inches cubed to centimeters cubed nah but what is it you know Alan no you're close because what you do know centimeters some of you know centimeters in an inch everybody know that 2.54 centimeters in an inch so there's the one we can multiply by because that's the one we know 2.54 centimeters equals one inch we know that is that what you were heading for Alan if I think you said 2.58 that wouldn't make very much difference basically I was trying to show you a lifeline there Alan you threw it back so we know that we've got centimeters on the top so we want centimeters on the bottom so we'll just take a over a out of this so that the units work out except they don't work out because I've got centimeters centimeters cubed and only centimeters here so what do I do cube it we'll move that over so it's apparent you've got to cube the whole thing I don't want to just cube the centimeters I want to cube the 2.54 as well because that happens on each one of the edges that 2.54 conversion happens so now I know that it's going to that'll take care of centimeters cubed centimeters cubed I don't cancel out the cube because I still need it here on the 2.54 so I know this is going to be 62 divided by 2.54 cubed if you don't get that cubed in the right place you're not going to get the right answer you've got to be careful this cube doesn't disappear it doesn't cancel we still need it down here everybody's okay the 1 cubed is still 1 we're okay with that one so whatever that comes out to be who's got that anybody Alan you've got the calculator there 3.78 I trust you I may regret it but I trust you so if you're working with area or volume or any other units that are squared or cubed or fourth whatever it is we need to work with be careful use it in the right way oh my goodness we went way over didn't we why didn't you say something I'm sorry I was having so much fun we should end at 10 minutes I'm just having to start at every term sorry about that does anybody need a hall pass because I made them late for the next class my hall passes are universally accepted no sorry about that I apologize keep me honest if I go over tell me I blame you