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Basic Physics Lecture 20

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As make you feel better whenever a professor says there's not bases always end and I believe this will be the case again this quarter is by far the hardest exam and it was clear you guys all looked around and saw a pretty much all of your left here and that means it was hard I know it's hard to say how are we take that into account in everything we do it hired Because both conceptually and mathematically forces the most intensive part of the course you're dealing with actors that make it mathematically hard being components due more algebra yards that wider the DOS I am conceptually you have to your call and rebel force I mean that a gerbil for Jewell accelerates A shoe So You may not be very few of you who got that last fall on a 100 per cent correct It was a hard challenging problem that's where we want partial credit 1st your answer working it out go over a carefully the best trying to learn stuff It is during an exam trust me I meet all the stuff the only step I remember from colleges the stopper got wrong so so you want to use this for the final exam in particular is Very key for preparing for the final the combination of last Thursday's discussion and the exam between the 2 of them you should have a really good handle on all the subtleties of forces in Newman's laws in force of friction by time not and be much better prepared for the final so please use them wisely Any questions on that that what we do this week is energy
And I I was going over what I did last year and it was very clear that this particular lecture by seeing the cause the most confusion out of all the lecturers so I've attempted to revise its son will see if it still gets the record for most confusion so hopefully will avoid that leave 1st thing to know the units of energy er Jules which is equal The new intend meet as recall from work What makes energy a little Easier than some of the other topics we have Is that it's a stellar we know our afterward are components when Miller about direction it can be positive or negative on but at least we don't have those issues now the other thing about it however that makes it a little hard is there are many forms of energy and it can leave or enter A system so you really have to end this accident think carefully about what you mean by your system a red talk a lot about that today but also talk a lot about what it means To change for It really means you wanna come up With the way To trap energy as you do the problem and I have to away To make my wife is not look like to you on that there are 2 main ways that I will use a table at a bar chart to be honest I like free body diagram which require you to do when it comes to to energy Anakin required a particular way of keeping track that's really I give you a couple laughter because it is so many ways you could do it you want to do with most comfortable for you so you can keep track of it but what you need always Do you think about it there's a few things and every response required It either I would suggest putting it in your strategy but will be used as 1st defined that you will always needed to define your system that year or using energy and a problem but you do not define your your system you will lose points and it's not just an arbitrary thing on our part he literally cannot not talk about energy unless you define the system so it's it's not arbitrary Part like this is not to make you do busywork visitors up Fact energy it only makes sense in the context of a system that inside that system There may be lot of different types of energy are different hybrids having energy better go back and forth between them and then there may be energy coming in or out of the system we are already saw 1 way that this happens right if you do where you change the energy of a system you there Take energy out corporate energy and so that's what we're going to be focusing enough now to trying get at these concepts by flood were the best things the think about is money money is always good to think about unless you don't have So Morgan girls series a quitter questions now and what I want you to be focusing on bidders was idea sister are we define a net change of form an exchange between objects because an underlying Olivette's is gonna be an idea But We can conserve energy conservation of energy applies which means that change and the Toro energy is 0 then the problem as much as you do so ironically when it comes to a final exam last topic we learn energy conservation will be the 1st thing you wanna try to solve any problem with it is by far Is this technique And you couldn't solve it using energy conservation Adobe much is your problem now with that ensure that's correct tour quicker questions so Leger question 1
You get a friend a 20 bill and they did you 2 10 bills exchange question is his money conserve Frio conservatory your friend is a conserve the entire system of your your friend follow the above but they re pretty much all got it right while 64 per cent listed on the Milligan this 1 we start to see the 1st idea system there's year and your friend so you can choose the system that might be be system 1 you can choose your friend as your system or you Jews both bond together now in this case system 1 starts for 20 dollars and how much end with 20 dollars so your money cancer yes adapted it changed form that what was attributed with a 20 bill
What was it afterward to attack That would mean legends of 4 so that might be view bruising potential energy and gaining kinetic energy of the same Now so you switch round Potential diplomatic We have the same amount of energy what about your friend they start with 20 and hammers There will be And what about for the entire system was a start with 40 and what is it and with 40 so rat So in this case all the way up Now we ask the obvious follow-up questions You give a friend a 20 bill a nice person your money is to serve four-year for your friend or entire system during your friend Ali Bob Knight about interesting What were Where Where Split all all over the place a little bit here I go to the actors as they used it for the 1st flight and talk to the person next year but again because you're not all right some of your over the game might bad Like it back Burning Worried devout while would get back 92 per cent of your brain 5 4 0 are ready to move White Exeland C is safe because Forget we have 3 different possible systems here Dead We have euros your friend you in your friends you just lost 20 dollars money was not conserve your friend gained 20 dollars money was not conserve but both you Had change in money that was 0 right 20 does went from 1 of you to the other view now 1 of the things that happens is if I make my system big enough money is always conserve and some say with energy right because they I figured you get in a paycheck adjusted to money was not the sort you just got money but think of you And the company paying you money was concerned and so on and I can make it bigger and bigger and bigger and money could be conserved Sun-Times that survey that useful anymore you can't solve the problem so you have to be a little bit aware that just because You may the system big enough that energy was conserve it may not help you figure out where when and how it went Like for instance this might be an example where you had no idea Had a computer you just knew there was no change in money but you don't know where it ended up there will you do with your friend or not that made any sense hopefully they'll start make more sense we to do more problems so money is conserved now you're friend a walking along and find a 20 bill Money is to serve four-year money is conserve your friend money used to serve the system of your new friend all the above 90 about I think we got a bag of rice Judges Wyaga alive and suddenly you in your friend and toward a more dollars a nite flight over right now so I'm not as whereby made the sister euro your friends and the sidewalk now is money cancer deaths because they went from the decide what to do but it's still a dream you your friend aside workers still just 20 dollars right so wanted things don't happen when you during these problems have to ask yourself off the system I originally that lost money or big money and I better off making a bigger systems including the sidewalk will help solve the problem or do I need you something else like work or forces were to kinematics so that's the decision process should be going through in these energy problems Mr. during out is of my system big enough or is it to Now There's 1 obvious Other example that talk about you and around You have 21 bells and youth rather than I did as a demo I was thinking that but you know Mass fails to break down I withdraw the money people are scrambling around grabbing it is money serve for the people around or the entire system of you and room the above manageable excellent the rig up at an really What's happening here As remain is the big enough Nano table the room I meant encoder room to further my recent dollar bills and start in the corner finds right The problem here is is a great example of it really really hard to figure out where all that money went right some people might revocable but tropical apart in a city like dolomite study the corner somebody else might swallowed by accident You just don't really know where the money is going so it may not help you a lot to do with conservative but it it And at the end of the day this is what we're doing Wood energy conservation Right you will pick Some better be a 1st step You will then identify the energy and I would with 4 says I wanna quickly list for you want your choices will be Everett objects is moving that it will have Kinetic energy which I almost always writers K the saves space and that is 1 have and square We did better ready Evan object as rotating There is kinetic energy associated with that it's 1 have I Omega square You won't have to worry about in this class but I wanna let you know that there is an with rotating it comes up and other places you will face it again in the future but noticed what Wilmington a intent but you don't really have to worry about exams or problems it's a lot like one-half and swear by This is the same as mass and Omega South after spending review mode there's energy death you're Like a real objects and is our money in the room example you will have thermal energy which you worry about and 3 B passes the motion of all your either we will worry about adhere very quick urged them on everybody older hands now rubble What has happened you got warmer day that random thermal energy from friction so we will talk about the weird word energy lost or thermal energy which comes from the source of friction times the distance attacks over now that looks a lot like work some bought some places talk about the work done by friction and you can think of it that way
The problem is In physics we'd really like what we do work We really like to know The system is working on and system managers going to Uribe your hands like this which handles warned both of them surviving does this hand there's a force of threats and find they understand was a force of forging of on this and where that energy Golota went about so much better the vigor of friction as Inside your system as part of it That turned energy into those random thermal energy and that's the language use of the problems we do And do all we see putting Inside the system gives you really know what happened to the energy that wiped out the other 2 that will worry about Are both But Chen Joanna is or And 1 is from gravity and will see the change and gravitational potential energy is Ng the change of And from springs that changes the potential residual spraying as 1 F K X squared so Would force is we have a whole bunch energies we only really have These widened to 3 4 that will be worried that A total of more straightforward And cut So will be putting those in the marriage problems a C will come from will talk more about where the potential energy comes from but just like an our money problems right we kept track of Crew had the money And while Denomination was the money in these problems were room which objects has the energy and what type of energy and you're bad all add up and that of your Toro energy and AS there is work by your sister The big idea that we will have a total energy is conserved so the change in energy 0 And that's that's where we're really going with for this section Questions I'm now Yes we Baby Elora start Britain out counterfeit money that's not real money so Europe So if you make fake androgen Lotus request not actually 1 of the things that I wanted to be slightly philosophical European make Monday by counterfeit money only lasts until the right and quantum mechanics union create energy for a certain amount of time the uncertainty principle and that it disappears That's Kolekar counterfeit money I make an analogy to go my life but most any other questions Now there is 1 those always gets tricky There The connection between potential energy and work this is the wine conceptual difficulties and the sections we have and the reason it is where does that all chapter on work and we did it in the following sets every system we checked was a single-particle soap Indeed Wars The West External to that article right Any force the problem a cave that force acted over a distance it did work illegally in role from X 1 X 2 of F . TX and that caused A change of energy in this case The only energy order It is kinetic energy now If there's a force and particle It is doing what was the only way we get a force Now cause acceleration so there is an acceleration you know there was a force was the other way we get a force but Europe Lowell beings and do we always have an actual physical contact for forest Now right because But Right now is my friend got some weight weight Yes that was an easy 1 is a touching OK so we can have a force without for what is it doing with the Interactive to get of course I did harmony objects That's reserve all right through objects interact negative for snow for any force I have I could say Those 2 objects and make them my system and now we have the idea of an internal force a came drove forces a little trickier what internal forces do right Because there exchange energy from a duet In a way that you get it Back in which case we can call it a conservative force or they do it in a way That's a lost of thermal energy in which case at the not conservative forces boy goes into the system and some other way they were not getting it back now the number We we now need to shout about conservative and not conservative Forces and this is where we get the connection to potential energy and the ideas of following for conservative force and gravity as our main example so they visit my initial And this alive final Right went from Say why equal 0 2 white people's wife final I he learned Take my objects as my system What's a free body diagram for that object Let's make it easier actually butts ever subject starts herein ends here nothing else tuxedo What is the freebie for that object weight down How much worked as the way FW times wife remembered we did last week and that'll be the change in its kinetic energy Now that's right As my sister whatever my objectives now they might take my sister as my objects plus the earth What is the free body diagram for the axis
Up Talk to the person next to figure out what is everybody diagram for the object plus the If a that Time OK anyone 180 a free body diagram Act How many forces my free body diagram family People think there are no Forces a freebie And maybe Boeing there's 1 Fort Avenue in 2 forces renewal in those 3 or 4 days what wrong we don't draw the forces better inside our system ever we only draw the forces acting honors system There they are once again cause acceleration that was our rule of free body diagram whether we realize that or not and now we have to realize that we need awarded before Because all or other objects personal objects but with 2 objects jolly forces External and there are no external forces so the is Iraq Yes That Now we ignore that the sun exists on the rotational era there's not a force 1st about saying Oh yes the sign is acting ravage initially on the earth And the object but right now in this room anyone feel any motion that I want as weirder before class on soft so it's 1 of those approximations remit with Just live in a world with just the Earth and the object nearer But There would order Berman or son now you might no problem with the room or the Earth and the signed but be given far more valuable that question you wonder ignore that now we're a problem if this is sitting near people zero-sum leaders like goal but what is it doing just before its around well at back in said yes accelerate that thing but more for part of it is it moving or not moving does abroad is Israel and will read not as well as easy questions go for It's moving you let go of it right it was a fine so where was 0 0 with a clear change of energy because our final kinetic energy does 1 have NBA Finals where that our initial kinetic energy was 0 Went nowhere The cause a change of energy what had happened well once we put these 2 together as a sister We do have But Internal So now We introduced a new idea and that's what potential energy it takes care of accounting for the fact that internal forces are basically doing the equivalent internal war don't figure that way Our attorney in what was 0 kinetic energy into now a lot of kinetic energy and that's why we call it potential energy has the potential to become kinetic energy and it's deeply connected to work because the way we get the formula for Change potential energy which was The final minus the initial So you as a common symbol for potential energy is equal the miners Vienna roar from the initial a final position of a journal force between the 2 objects times DX There's often ran as the negative of the work now it's a weird thing because as the wire That is drawing gift The force was axed over system The problem is I'm I go through this to the border Thursday but here's the warning for you What is the most common mistake students make They do the work done by gravity but is potential energy due to gravity because it can stop and thing about system that And they put bottles formulas and which are the negative each other And things cancer ladder double in the ghetto problem There's no way when I to objects and 1 of them is earth user either by Near system for Only the abject So you have potential energy for work done by gravity you don't have both It is just a way to calculate 1 as a formula Separate from doing the problem to show that there's a connection that internal forces chains energy through a potential energy and uses a formula But even from P.O. If they knew the work it would deal as the negative of it now This is what happens for what we call a conservative force by different thing will happen will talk about that I went a little bit For not conservative forces But when you read about this in the box and this is 1 of those areas were really your 1st time through physics And is a comeback and 3 B it actually will come back and number by biology applications to take biology it comes up in chemistry you you really have to take this through different steps and it might be the 1st time you've ever seen at 1 suggest students is what manager problems forget that we learned about work and bigger system big enough news energy is your Lucerne forces that you could never put in the system of the shop yet The work by them EL submitted energy that 1 way to do that there are times it's a little easier of you think of it as work that but it always saw with energy and then that helps awards confusion as you work thrower and learn more this relationship will start to make more sense any questions on that Or that that means said if I do this for gravity The force of gravity is always energy and ever my standard X and Y Gd as always And the negative y direction and my work this out I get a minus a minus Ng remembered not product tells me take the component parallel the force so all I had to do was white So you're wife final miners wife initial by 2 minus signs canceled And you get the formula I had earlier bandages times wife final miners why the show which is the change of light and so I now Consider the energy my system to include 2 pieces my kinetic energy and my potential energy and there no other forces if there's no war men might change and energy is 0 and I just go back and forth Between these different types of energy and I can see where this starts the possibly be useful air by now I've got the pieces is I saw offer the other piece where And now we have good your fund demo where might That command thereby I was swinging a bowling ball widow about sway Right now it's all about initial There's another There's maybe a final height starts with 0 speed What speed might have when it comes back so you'd hinted that up you put it
Right now objects You're in Swain yet
If that I came back and get that object so you Livingston here
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Are dead It was not doubt But yeah What I always leads a little bit but Well the gamma We join media which What was the difference between me and the camp wider make that can get knocked over And I think that in the face and that is the question I want you to meditate on for Wednesday and because of that may because take this down before the next last surrendered a few minutes early so meditate for Wednesday do your homework for tomorrow
Iran Lanquist Aware that
Hufeisen
Kombinationskraftwerk
Elektronisches Bauelement
Donnerstag
Leisten
Druckkraft
Übungsmunition
Woche
Ziegelherstellung
Edelsteinindustrie
Innere Reibung
Ersatzteil
Herbst
Gewicht
Wärmeaustauscher
Potenzialausgleich
Direkte Messung
Parallelschaltung
Hybridrakete
Leisten
Antiteilchen
Satz <Drucktechnik>
Korporale
Feldeffekttransistor
Computeranimation
Schlauchkupplung
Stückliste
GIRL <Weltraumteleskop>
Telefonvermittlung
Kaltumformen
Elektronisches Bauelement
Elektronen-Energieverlustspektroskopie
Energieeinsparung
Teilchenfalle
Gleiskette
Übungsmunition
Tonbandgerät
Gleichstrom
Jahr
Ersatzteil
Stückliste
Erder
Leisten
Spannungsabhängigkeit
Satz <Drucktechnik>
Computeranimation
Woche
Prozessleittechnik
Montag
Telefonvermittlung
Austauschwechselwirkung
Kaltumformen
Rollsteig
Längenmessung
Wärme
Schaltelement
Übungsmunition
Gleiskette
Weiß
Jahr
Öffentliches Verkehrsmittel
Stückliste
Analogsignal
Synthesizer
Fliegen
Drosselklappe
Gewicht
Masse <Physik>
Schnee
Erdefunkstelle
Antiteilchen
Feldeffekttransistor
Be-Stern
Teilchen
Holz
Spiel <Technik>
Pfadfinder <Flugzeug>
Edelsteinschliff
Stückliste
Urkilogramm
Steckverbinder
Windrose
Elektronen-Energieverlustspektroskopie
Tag
Energieeinsparung
Takelage
Minute
Türglocke
Druckkraft
Schiffsklassifikation
Koffer
Innere Reibung
Source <Elektronik>
Gummifeder
Ersatzteil
Erder
Kugelblitz
Energiequelle
Sonnenstrahlung
Gleitlager
Bergmann
Einschienenbahn
Satz <Drucktechnik>
Feldeffekttransistor
Computeranimation
Platzierung <Mikroelektronik>
Rotationszustand
Trenntechnik
Kette <Zugmittel>
Urkilogramm
Druckkraft
Steckverbinder
Kaltumformen
Koerzitivfeldstärke
Licht
Elektronisches Bauelement
Intelligenter Zähler
Donnerstag
Tag
Standardzelle
Rauschzahl
Flasche
Druckkraft
Schiffsklassifikation
Werkstatt
Eisendraht
Atmosphäre
Gleichstrom
Lineal
Ersatzteil
Initiator <Steuerungstechnik>
Fernsehempfänger
Drosselklappe
Front <Meteorologie>
Besprechung/Interview
SOHO <Satellit>
Drehen
Besprechung/Interview
Passfeder
Gammabestrahlung
Mittwoch
Minute
Elektronische Medien

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Titel Basic Physics Lecture 20
Teil 20
Anzahl der Teile 26
Autor Dennin, Michael
Lizenz CC-Namensnennung - Weitergabe unter gleichen Bedingungen 3.0 Unported:
Sie dürfen das Werk bzw. den Inhalt zu jedem legalen und nicht-kommerziellen Zweck nutzen, verändern und in unveränderter oder veränderter Form vervielfältigen, verbreiten und öffentlich zugänglich machen, sofern Sie den Namen des Autors/Rechteinhabers in der von ihm festgelegten Weise nennen und das Werk bzw. diesen Inhalt auch in veränderter Form nur unter den Bedingungen dieser Lizenz weitergeben.
DOI 10.5446/12931
Herausgeber University of California Irvine (UCI)
Erscheinungsjahr 2013
Sprache Englisch

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Fachgebiet Physik

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