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Basic Physics Lecture 14

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OK drive heading that started our lives up
Political picture roller-coaster some combat Quayle Very must be I did quite well that is a lot more green than there was on Monday dose Now the next quiz will open today and will be due on Wednesdays lecture Now known as the biggest area red people are still trying to call something the centripetal force there is no centripetal force but we repeat that there is no centripetal force there is A centripetal acceleration And if you have a habit of chewable acceleration there but did that Forthcoming from lots of sources That provide gerbil acceleration but it'll be a cart usually a combination of many forces and there is no force That is the centripetal force Keep that in mind Other than that quiz look very good A mail The other great things from the Cortez
And I'm gonna put up It was nice comment from it and the reason this is Very useful a number of people made comments like that and not as a phrase does friction Kantor component of gravity that pushes the black or is it countering the forces supply number people said this friction and does not count our forces protect so that's going to be a source of confusion for you if you don't get rid of that idea Does not oppose forces Frank said A positive Attempted motion so you wanna go back if you were thinking of it as Friction opposing forces you need to go back particularly that series by showed in the website of the 3 blocks with friction For 1 version to urgent threat because it really get that this idea of friction and attempted motion also the few blacks and top of each other additional podcast focuses on how do you identify the attempted motion that fortune is going to oppose every remember a strike because If I ask myself I walked forward you would think my attempted motion is moving forward and so friction should be backwards but The attempted motion is my butt pushing backwards on them More They so the intent motion is sliding backwards so Correction as forward and actually makes me move friction is moving you forward So that there is no force opposing in that case because that's not what friction does and opposes an attempted motion questions on that I'm really good this is less than the quiz exactly his way the does highlight What are the challenges with friction Now the
They just to remind your bad luck at kinetic friction does show up whatever the is moving whether it will be constable losses or whether it's moving with the change in velocity news kinetic friction static returns lawyer that that When it is not moving And when it's just about to move but is not moving accelerator That still static friction once it starts moving that phonetic searches and again that sequence on the block on the ramp will hopefully clarified that question so today we're doing circular motion there were a lot Barracks What happens with actually Bureau of treble accelerates the magnitude these were rock and a dollar in the direction resume that means radially inward and it could be an instantaneous Acceleration is changing But it can also be and is a logically doesn't carefully still an instantaneous acceleration with a can't stand magnitude of Viva speed is constant but not us Moving in a circle the direction is always changing so this is never constant acceleration so I could never a common Eric some point is you see a circular motion computer accelerated toward a bar and then you plug into equity the accounts acceleration Does not work because it is not can't acceleration is a direction as they move inner circle right here is because my spit thing a circle right
As I move in a circle the directed radially inward is always changing so directed his changes at now
The other thing is there are lots and lots of places where you get circles which is why
I want to keep the rollercoaster out you should be a Right here these are vertical loop the loops right there's charcoal and their vertical so radially inward is down when I'm at the top of undecideds parallel to the ground when among the bottom radio and word is out to sea radially inward as they set always changes their circle here as roughly horizontal goes a little bit down a again radio inward is always changing but it has always be horizontal may be slightly tilted so we have circles fundamentally at any angle but the dominant ones
Carter have circles that vertical An horizontal what problem Tuesday with us to pictures Which 1 was but label which ones the vertical circle John so you really have to go picturing your head Where vertical or horizontal white is matter whether vertical resigned or gravity right by Free body diagram in this Based on the undertake XOY like that maybe my object to this year I met my object that I will have weighed down in this case normal force to the right and that That's why this object I might still pick a wife But that that's why is it really would be useful so I don't want that 1 because this might be a horizontal but other strength so it might be spending like best That's horizontal spending is horizontal circle but up-and-down for gravity still matters so when I draw my picture free body diagram that I have Say Exeter why I'm still gonna have weighed down I might have on those in some tension and a string like that that was my string a on circle but For both of these in this case at this point out that way Some ice and chewable acceleration that way At this point I'm that way So with this award system I think the ax so that my censurable acceleration is a long acts As I move around you know over here I'm up there and I'm in red I still have weighed down by now my normal force went down notice in this case moved over here and of course my Setubal acceleration is now down if I moved here In this 1 way is still down I have changed my ex X is now that way And so might send to looks the same MIC gerbil acceleration looks the same I can't do that I can move my Ford system for this 1 right here I picked acts that way evicted the other way Ledger marrow to the right Where are the right there but the point me being you have to keep in mind whether you're moving your corner system At about moving in the plane like this The bomb flat usually still always out the gravity and a at around the lineup with me all I care about that radial direction that interprets operation is what I'm going Article I tend not to move my coordinate system Because I'm gonna need to use gravity work Gravity is in the wider erected annexes just in that plane of my circle and it said at least centripetal acceleration will be where it is So this is Probably the 1st less confusing think about moving in a circle Questions on that yes We can They are that's why they have acceleration so really That a more detailed but notice when I move from here to here I moved toward the center I'm close to the center I was before now notice right acceleration is the change of direction losses all the magnitude it doesn't necessarily mean the directs your movies and that's why the biggest pictorial confusion comes from and wouldn't do a lot with the best of my velocity is that way and my acceleration Is that way all that tells me is that next time and I'm going to be moving a little bit down I changed my velocity and the direction acceleration but does not meet in the next instant by regularly inward and my velocity was that way and the time it took me to move down a little bit I physically moved over a little bit so worried over a little bit And down a little bit overloaded and down a little bit and constantly doing that makes a circle So it's centripetal acceleration and that is really why you're moving in a circle so you know when you're moving in a circle you hats triple acceleration they go together it's kind of an differed only and you'll see that some examples we go there is another question What say A year We don't know yet about the role of the magnitude of notice in the vertical case at this point At a right angle I remember any dealings a writing or independent so in this case what we see is the normal course being in the direction the center of acceleration is completely responsible for and gravity has nothing to do with his centripetal acceleration and as do a speedy you up as you go down the circle when we do a loop your speed is changing as you go around and will see that over here know what's happening in this picture Attention now has 2 components 1 in the direction of gravity and 1 in the direction of my centripetal acceleration so depending on relative magnitude of be compounded the opposite gravity that'll determine if I could stay flat circle right so of spin this flat and circle I have no acceleration vertically acceleration vertically the component tension has cancer way of ice Many of those theirs Right where it's falling the circle in smaller since its following clearly weight It was bigger than that component attention because it accelerated downward as well as moving in a circle tricky enough
So that you you just have to Ali's picture perpendicular directions think in terms of components with forces you really have to do the best with a picture of the asked What is the acceleration in each of us to direct and often 1 0 and 1 will not be 0 but sometimes they'll both non-zero excellent questions anymore Ever Bond And be a little more clear Ms. visitors but you may You Yukon used polar coordinates aren't they An area planted not really needed Because were always going to be asking for you about the motion at 1 point and Do not be asking about it at different points in the same problem you just pick connector courted for that motion and that is used to do since we don't move around where you're really doing is taking a few support portents are they But as a riding on the net change in weekly column that someone other questions so rail quickly before we get into but by 2 think of what is Where some examples of the motion weary sigh 1 we saw roller-coaster loop That tends to be vertical we saw strain on a stranger with a rope which unfortunately to be vertical or horizontal that tends to be vertical right at his villa in the circle like that But over my head like that you're brought on seat does anyone remember what a record player is that of those records spinning around on the Avenue noticed you're you're cities to spend so there's lots of examples of spinning disks that things may or may not sit on the merry go around right y'all remember those those Rotator horizontally and there's cars turning and back and wanting to remind you often have a bank heard this is something you need to learn the picture so In this case the car business from the side from mobile The car is going in part of a circle but it on a banker road so they centripetal acceleration is still radially inward But now you might decide to pick 1 of our slanted corn systems or you might decide OK I really want Acceleration To be along axis and you might take a normal life The 1 case on a banker were not always clear which acceleration you want a pet so the user things you want to make sure Questions on and lots of others But his debut a few The other thing you wanna be aware And we set here Right with the thing going around the roller-coaster ride that divide through the free body diagram here there is clearly unbalanced forests in both the X and the white sorry mix them up and both the X and Y directions this means I have an acceleration with both an ex component and a Y component in this case the x component is the radios and Joe Blow acceleration discord over on the Y component is whatever it is coming from that works and Soviet total acceleration It is a square Road Of these 2 square and maybe at some angle right will have A acts A Y and the total acceleration will be of some angle theta where his usual attendance data is a Y Over text so there will be a few problems where you're asked for the total acceleration but you have to just mind that It might be speeding up so we call this 1 but tangential acceleration of its tangent The curb your moving and it's the 1 changing your speed The radial acceleration and triple acceleration that corresponds you change in your direction Questions now we have to find a polyostotic quest Yes No it's being turned toward the center Do you know you're actually being turned toward the center If you weren't being turned center did leave the right I would do that right now a there's there's carnival ride that commercial right your brain your brain and Your ideas that the right and the right has a vertical carnival ride A new around a vertical circa like this without a seat belt ask fall out or not collector questions Now there's 1 is phrases water and the by organ or water in a minute I don't like to start with water like that a warm up enough takes on every year and this is like Sea World by the way those 4th 3 writers you may get wet I'm just going around and the question is is it a fallout out matter how fast they spin at would database basement fast enough What is really happening the bucket cheating you must be both bank thereby fast stays and so sure enough That stays it as I slowdown Starting The Ryniker back-to-back So now the question is
Will this work with water The I just realized I forgot to practice however stop with them I'm sorry
South where are we water A 4 out of the car and that would end the war
At the last minute so Eva work through water so you wouldn't fervidly say that your seat belt a driver off the right by the X. quarts of water
And the real question is why right what is happening here
Then there's
Yet to be halted issue at moving in a circle and what is it really me out If we lack At the top of this way to that Really the most dangerous point were we expect the fallout were completely upside down I would ask for it Free body diagram on ourselves now there is kind of a side of the market so there could be some friction there that household you want but you know was water there's not really any effort to trim the water in the side of the cup it pours out Quite easily as they demonstrated when I spoke at all over everything What is like that so there's no real friction there but it is interacting with the bottom of the cup tour normal contact Which can really only point down and of course it has weight so those or 2 forces on map in this case I can take up to be positive which wooded area might assign values what do that because it's a common way the ticket now we know at the top of the slaying The but it and the water Is moving to the right side we know that about the top of the swing What happens at the Top of our motion by definition it are description of motion to be that remember kinematics and how we describe motion What happens at the top of any motion The vertical velocity 0 which means moving parts we horizontally so Dance The total force was out better acceleration with equal 0 and we just keep moving horizontally so there would be no change in our motion And we would fly straight that way and that should be what happened but there are Forces are now dead The total force It is greater than 0 they are acceleration of greater than 0 which way do we turn up or down In this case but knows which victory positive but because of was positive I just you a total positive force It is a positive acceleration Sarkar would do something like that we would occur but now In this case are total forces negative now which way we got down notice The positive and negative isn't really the relevant think it's whether the forces down or the forces out which defined from our plus and minus I'm recording of our forces downed weaker down that you're used things falling curbing down because there is almost always and which direction is Now so nothing stays going straight right It's It's always Kurt There also is the question of the normal force however and what's going on there A mail What we wanted did is movement a circle with a radius Ah which is what I was doing with the back I need an acceleration equal to the eastward over art that's what's triple acceleration me if I'm going to go in that particular so this is a special case Laid down curve And so what we need to do so we look at the far away we write down was going on and then a right F normal in red and currently make it just positive because they say we don't know which way it is and then we know waiters down and the questionnaires and that Therefore whips letter-writing energy for weight and we know that has to it we wanted to go on a circle people miners and be squared overall are and that will make us go in a circle Now this means therefore GTE equals These squared overall Then And The 8 0 0 0 to go in a circle right Because of Jedi as people that I can't have any effort this would be what we call just make it Because My normal force went 0 are now what happens there The Jedi It is blessed then square over or forum going faster anyone wanna say what would happen then if GE is less than these word over are to achieve my circular motion What has 2 things that never happened I need to make my top equation and equality and I'm telling you G is less than discord over I'm spinning faster than I was just make it What now happens has no positive or negative Mulligan Michael where wrote it but this is too small and as a negative number what was this big negative to make it up right so I this Point and must be some negative number which is broad Because We know it can go down so we're OK So by Sprint Baxter that what's happening right noticed spinning faster would mean a bigger acceleration So I need more force so do achieve my spinning faster I suddenly needed to use my normal force which is down and negative if I go to slog of Jews greater than discord over Which is going slow or we want the FAA to be positive which can not being unless some also attached So you have a seat belt order physically attached to the track for 8 years super glued to your seat Right Then your normal force can point up right if I'm physically attacked by normal forest and point out which is what I need to keep me But in the circle of this case but my red wine is a circle I want right what's happening when I go really fast gravity would only allow me to make a circle that big and the normal force pulls me And let me achieve my circle pushes me but I'm going to swallow of gravity is trying to make a circle like that and I need a normal force to pull me up because is where the Barker because my hand is pulling the bucket there and everything else falls out a less I So those those of the main concept you 1 I have right now in your head so let's pause there for a moment fear about this look at it from a view many questions in a renewed example problem with
There was a lot on this slight yes Of these where over are the whole thing is an acceleration These as squared over 2nd spread so I defined by a radius I get meters per 2nd Court So what does something If you like it there were trying to explain a summit was 1 thing you could take away from this What happens to to the normal force does it have a set single value About the value of the normal course will change depending on the situation or what it needs to be With a rare right when I put something flat right now the normal for some reason people what whom I wait and see to them on the side of a hill gravity dam normal forces perpendicular is less than that changes now wait I'm spinning around in circles it gets even more complicated because the normal course And just as needed now Obama drawing and friction Particularly static friction that get even worse right is the normal course just as needed static bridge is less than or equal to the normal force just as needed to yet to things that are just don't pay attention to you see where the problems might be questions so now having said all that lets answer quicker question number 2 Now that most of you cancer this is 1 of those rare cases that I would say it truly is a trick question and were done it is They and the reason it is They think it is It's a art that is generating the normal force What I mean by that right There's a bizarre tendency that keep moving in the same direction we moving so the top I wanna keep moving straight but but a the but it's moving down and I'm trying to move straight and my desire to move straight but fires the bottom of the plot They generator normal for them me down how that only needed when I'm going really fast right there was special case Were all out of these centripetal acceleration was generated by the force of gravity itself And so it really is a nurse That causes you to stay in the bucket you wanna keep moving straight The but it's turning forces happen on you to make you also turn with the bucket the subtle point you know it's not really 1 I would ask specifically On test in this way But support you realize when you look at any situation object Wunnicke moving straight so they're only gotta turn it a force on them to generate that change in velocity at that Forest to be from many many different sources as you have to pay attention of them so Let's The problem but like I said visibly roller coasters that we look The Bureau spinning around everything's moving sideways and tables The merry go fictional sometimes somebody is normal Sometimes of gravity 1 thing please pay attention to this is not really meant to trick you that's just the way it that's the way problems awarded for lots of different reasons I tell you this case how high the Lopes White It is the about physical dimension that goes into the center of a row acceleration radio What is the radius of a 60 meter Iowa State meters What's that it is an e-mail me a master visitors can get those right I get answer wrong every time I will probably not respond because they divide by 2 somewhere so that In my would further question this is how fast are we going and we just make it without falling so just make it That their keyword Reever normal forces 0 so we gotta do this problem we have our look which is 60 meters we're at the top organ APEC down to be positive Britain Drive free body diagram there's only the way normal for equal 0 because we Just Make it we know we have an acceleration of discord over are in a downward direction really word not as I do not put the acceleration this right here is not in my free body diagram indicated separately so I don't get confused having done that I use people made so I'm gonna have F. Wait equals And square overall are the way I know as MG noticed my NASA's canceled I would not need to Give you an mass in this problem and east where he was due times are or vehicles the square root of G Transarc And I into that I will get a . 9 meters per 2nd That is kind of good quarter Recent triple acceleration problems the most basic version Identify accelerates you identify all your forces you're generally solving for something in this case resulted from notice As you go for it in this class this is a great situation where there's lots of ways we may or may not want to know about these your local loop was brokered coming down the rollercoaster you and it suddenly at the top That I ask you where you went over here what I do is I want I you you when you leave a little while you're there what type of mouse Project emotion your invisible his words are not and projectile motion If you needed to know your initial velocity You would find it for method was that Because up until this point just as you leave you are doing circular motion you know you just make it You know the acceleration right here was eastward over are so you know now you're flying through the air At speed 8 . 9 meters for 2nd horizontally you were not Doing accelerate your no longer circle now Only have gravity and protect our motion for a new use everything we did in the 1st 3 weeks I now connected to problems and you hopefully don't went for went to Questions on that Now with the 2nd part of the problem by the way I really encouraged most of the problems you do in this section stop and think OK Professor de turned that into this Plus a kinematics question just think about that letter said Mark says Would double that speed now wants the normal force that was turning around that now we know the speed something about the forces
So now we know we're going faster so there has to be a normal force so there is our free body diagram we still take down to be positive And now we have F normal class energy as in April and vii squared let's call it to Dover are and what we know is to EPA's twice the velocity we had before Now you're club tries the point of just plug-in twice that velocity numerically but as I said I'd like to do these algebraically all the way to the end and then plug and so I would plug in here Right and this equals 4 times the mass times the velocity squared overall are and I know what this I just did it up here right If I take That equation which I had used I look over here and I see velocity squared over is just G and said Now that's people's 4 and G and now I have F normal plus Angie equals 4 MG which tells me F normal just because 3 MG now I do need to give the which I do and the problem and when you plug and you get 1800 new so a in this Simple Problem right there may not be Clear how that is really useful keep but as a variable But a lot of time with the information you're given you may not have been given initial velocity a may never solve word for some reason we you would had that equation and by keeping track and is due to pulling out you would have known substitute for G and get your energy so there are times and places where it's really helpful to keep everything as a variable questions on this problem Jack Questions for sure But that was given as 60 meters right there Now rail quickly so let's just Review Are you you have an overview going into the weekend as you got till standard official this homework you're focuses the F peoples and made inappropriate X-Y coordinate system you need Dipped at best and it may be tilt that You need to ask water all the interactions going on do I have weight do I have Friction what tight do I have a normal force do I have any pushing or pulling do I have any robes retention you have ask what accelerations do I have I might just about to do something so that that's telling me an acceleration 0 is a dividend of 0 Or some other constant is circular so that I know I eastward over art and then you have to focus on Where you been asked of flying so you know put all the pieces together to see how this is much more complicated than kinematics 1 way But details there are more details and kinematics we just that basically cause acceleration 4 0 accelerator which was a special case of constant celebrated and we had a two-component and that was it 3 user 2 equations a lot here we still really only have 1 concept that but we have way more details you have to keep track so that was rather be practicing so you get the idea that it's all just 1 problem even others like 20
Phonograph
Greiffinger
Drehen
Bombe
Magnetisches Dipolmoment
Spin
Satz <Drucktechnik>
Minute
Computeranimation
Rotationszustand
Rungenwagen
Biegen
Rücktrittbremse
Sicherheitsgurt
Zentripetalkraft
Elektronisches Bauelement
Telefonleitung
Rootsgebläse
Übungsmunition
Kugellager
Spin
Tinte
Knüppel <Halbzeug>
Jahr
Zylinderblock
Ringgeflecht
Frequenzumrichter
Radioaktiver Niederschlag
Drosselklappe
Gewicht
Ruderboot
Masse <Physik>
Stringtheorie
Dienstag
Hobel
Dreidimensionale Integration
Feldeffekttransistor
Wollspinner
Zylinderblock
Eis
Pfadfinder <Flugzeug>
Verpackung
Beschleunigung
Munition
Druckkraft
Trajektorie <Meteorologie>
Schiffsklassifikation
Scheibenbremse
Weltzeit
Schlagwerk
Gleichstrom
Innere Reibung
Sprechfunkgerät
Ersatzteil
Tuner
Unterwasserfahrzeug
Erder
Evapotranspiration
Fahrzeugsitz
Hydraulischer Aufzug
Parallelschaltung
Stromschiene
Treiberschaltung
Weltall
Cocktailparty-Effekt
Woche
Uhrwerk
Kristallgestalt
Montag
Fahrgeschwindigkeit
Negativ <Photographie>
Messbecher
Randspannung
Schreibstift
Kaltumformen
Seil
Feldstärke
Querstromventilator
Faraday-Effekt
Canadair CL-44
Schaltelement
Gleiskette
Tonbandgerät
Weiß
SOHO <Satellit>
Atmosphäre
Uplink
Handwagen
Anstellwinkel
Fernsehempfänger
Kraftfahrzeugexport
Sattelkraftfahrzeug
Bergmann
Fahrzeug
Erdefunkstelle
Remanenz
Stoffvereinigen
Schusswaffe
Rootsgebläse
Antiteilchen
Steckkarte
Nanometerbereich
Trägheit
Aktives Bauelement
Quecksilberschalter
Dosieren
Flugbahn
Kommandobrücke
Steckverbinder
Innere Reibung
Kraft-Wärme-Kopplung
Theke
Windrose
Elektronen-Energieverlustspektroskopie
Kombinationskraftwerk
Omnibus
Eisenbahnbetrieb
Schwarz
Amplitudenumtastung
Nassdampfturbine
Zylinderkopf
Source <Elektronik>
Scheinbare Helligkeit
Mittwoch
Frequenzsprungverfahren
April

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Titel Basic Physics Lecture 14
Teil 14
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 10.5446/12925
Herausgeber University of California Irvine (UCI)
Erscheinungsjahr 2013
Sprache Englisch

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Fachgebiet Physik

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