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Basic Physics Lecture 10

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So what Iowa where are we and where we going we spent the 1st 3 weeks learning how to describe motion we realize they're basically 3
Parts to your motion as you move around the world the 1st fire is your position where you are But the cat And your position can change so we like to really focus on your displacement Which is your change in position so these are rarely widened issue And for pretty special case of constant acceleration and we actually had a waiter computer you're displacement give and you're initial velocity and you're acceleration and so this was A very key part of the 1st 2 weeks and This equation highlights for us that our displacement back here are velocities of actor and acceleration is a vector because Directions is very important when it comes to where you move to I'm here and I moved 10 meters this way is very different than being here and moving 10 meters this way I end up in 2 different places so directs a matters that was peace 1 of describing our emotions was our velocity from which bears are displacement in a time of intuitively were velocity tells us is where and how fast we are moving away being the direction a movie that we're moving that we're moving that whereby velocity tells me the direction a moving in and how fast is my speed how fast my do how quickly is my position changing and instantaneous velocity was a derivative A position with respect to time once again we had a special chased constant acceleration in which case are final velocity was related to a initial velocity by adding 8 times tea and again 1 of our main equations that we spent a lot of time So those are the 1st 2 pieces of motion B final piece of motion It was our acceleration itself which was odd change in velocity At a time in a row and wheat Worried about cases cousin acceleration but we also have accelerated change in time and the definition of the instantaneous acceleration was the derivative velocity respected time and with where's the velocity that complicated by the time overnight accelerators of Argentine we would take the derivative and things like that and those war for pieces of motion now but I think about death You go back and look over the last 3 weeks the reality is just a little bit of extra spot your intuition about describing motion is pretty I ask you again said Being class if I was asked by driving down the freeway I saw sign that your next 4 miles away you're miles an hour with the calculator you could figure out how long would take get And you most people without even thinking about it are doing these sort of calculations all the time do I need to go and I'm running a little late and you go faster how much faster ready to go out and in your also do it in the context of How much faster than I get away with enacting a speeding ticket so you doing these complex a sort of Calculations and you you have an idea of what acceleration is you can kind of feel it when your car accelerated Turner quarter direction changes and you feel that What really do next is described the causes of motion and that is something where intuition is not as good and so you're real again after played close attention so the way I do their bit today and Wednesday is a lot of conceptual quicker questions a lot of us will do some simple simple demos most today but got budget demos for Wednesday to try and make it clear to you wear your intuition is good and wears of fail why so you can be better prepared for doing the problems associated with The causes of motion so work We we just start by asking the question The bomb What causes motion in particular are causes of motion related to position and velocity or acceleration and 1 of the interesting things that will like is Where position X we're velocity which is DXT wave acceleration which is which equals the 2nd derivative of acts with respect to time because we comply game there The question is why I stop acceleration why don't I have A 4th Why don't I care about the change of acceleration in time and come up with a new thing with a new name the detonation Right because I am still looking at name Something named after me have achieved number of the dead in a fact I think that's got a nice ring to it So this is where we're going and The problem we have Just so you're aware of it right up front is you live in a world of friction resistance An gravity and be a dessert Invisible forces and you don't see him you don't think about on bank That tends to mess with your intuition And that's kind of what really trying break Over the next 2 days so there won't be a whole lot of example problems they'll be but That's where we're going a focus so reddish start right away with a collector questioned The key So I take a buck I slide on table Particularly stops right take the but I pushed the black The book stops enterprises were were asked about now the causes of that motion that I describe it as initial velocity of final velocity that moves distance and had an acceleration in the opposite direction velocity And that's why it slowed down but is not really a that distillate description of all the different parts so it didn't start because this is really tired and wants to be rest on a not wish On something to kept his moving it actually uses a All its energy so when you play with your that 1st heard a bunch of energy and that uses up that energy removed and Manchester stop all are More than 1 the above or none of the above I guess as to be object wants to be a rest don't not take it just because English is bad not saying you should Yet but I'm a physics professor we spell find PHU and so you can see the movie whereas motors point there they smiled but see where we are now must be aligned with none of the above are enough let's see what I went with Look at that I went with none of the above but I want out something very important in this context that even those view it with the but very good
You thought about a carefully pressure the exam you may not want you may not be so lucky this 1 1 and this 1 Were all views of physics before Galileo before action before new and even I should be more careful and end the reason mean without a really good understanding of a world without friction without thinking of friction as a force there are various ideas people had Objects had a natural state they wanted to be a natural state was at rest that was were everything wanted to be so the absence of anything happening to it you moved to your natural state which has been at rest that is related and the same idea as if it wants to be rest that's not gonna move you're pushing on a soda keep moving I have to keep pushing on and that's pretty much your everyday experience if you want something moving you have to keep pushing part of the 3rd 1 you know is another way Maybe using genteel your language to express those ideas is that The energy associated with moving adds I moved by music that energy so start out of the initial amount of energy was the mere act of moving users at an and that's natural from our own sewn into isn't what we do right As you move you get tired you feel like you're using your energy so B water even if you were very very good and the contents of the question that best best time think about it It was only a physics class writers For the right physics answered the pressure of a tester brain might take over your brain probably like almost all human beings prefers these as you know what's that A attention to it Any questions on that so I were now I ask you a question Flatter could request in early occurred without a vote is asking the question what causes velocity what causes an object to have some velocity so you see
Object moving say at 10 meters per 2nd GE's moves by you tonight 10 meters per 2nd what is causing that velocity talk to the people around you for just a 30 seconds what is causing that velocity as the object moves past Get out is it I account He was was also a a fog Jagr anyone wide I share would bake Bank causes bad Lhasa beat Yes but yeah force a pusher pulp possibly Anyone else shares Yes 3rd loss Possibly Anyone else when a share something Yes JJB accelerator Gaza last not Any other thoughts was put this in like Arad Not as Jazz is A random sample most people where it would be wrong answer when phrase that way even tho you probably were among the people who got the center-right and that's what I say your brain gets in the way it As far as we can tell not being causes velocity things Gaza change in velocity if at some point the object that when flying past due in the past was not moving at 10 meters per 2nd was moving at a different speed say rack that yes there needed to be a force the push Europol or some interactive lot to cause it to change from 0 to 10 But that was in the past but that's about as it moved past you at a constant 10 meters per 2nd flying straight what was causing that not Not being causes that Velocity now 1 way possibly see this bears to think of Instead of current your flopped on an airplane right now while on the airplane is thrown something to a friend in the back of your point excellent and you've lived to tell the tale That fight if you're an airplane so let the matter which airplane so here's my airplane writing you're sitting in here there you are a year throw something backwards and my airplane is going a 145 meters per 2nd in that direction and I the date for the back of the plane to be positive and relative to the air but a look at this were sneaking in a practice problem for the test who aren't supposed relative to the airplane you throw the can of soda Can of soda About 5 meters per 2nd eyes gentle tossed right view will measure the change in velocity of a can of soda Delta V BV final minus V initial which 5 minus 0 because it was in your hand that rats which will be 5 meters For 2nd back to me On the ground while you're flying a Wonder Woman's invisible jet when I see as a can of soda With an initial velocity of negative 145 meters per 2nd because it's flying with the playing to the left and a final velocity of negative 140 meters per 2nd because It's got 5 meters per 2nd relative to the plane the back and I that The 145 and I get my mind is 140 so I'm measure A change of velocity for the camp of V final miners initial people's mind is 1 48 miners a negative 145 Which is a positive 5 meters per 2nd but not as a couple of things about this And in these situations if it would a Plaza velocity that very weird and hard to come up with because You were saying it's going 5 meters per 2nd I am saying is going ahead 840 meters per cent and negative 140 meters per cent so we disagree completely I want the velocity So thinking about a cause of that velocity is hard to imagine however We completely agree and we will always agree on the change in velocity as long as we're moving at constant velocity relative to each other So we may not agree and add value but we will agree on the change in the value yes Earned At that What after my friend catches it because back to 145 but my friend and I decided goes back to 0 We see the same change again Adobe and negative 5 meters per 2nd that point that make sense So After the catch right noticed Once a Scott from my point of view on the airplane I see it go from 5 meters per 2nd 0 meters per 2nd Where A change in velocity of negative 5 meters per 2nd at outside the plane I see go from negative 140 back Negative 145 which will also be a negative 5 meter per 2nd change so even at that taxing moment we see the same thing in terms of the change in velocity and disagree on the velocity use again the plane says it's going 0 admitted outside appliances is going negative 145 Lagat said Today when there is all about his conceptual thing this just ask the following quicker question which is be actually a series of photographs when added to A warming yes and be will be no Aretha really quickly and start and stop each 1 and it's going to be position is that er is it not independent of frame Inertial frame were made possible to rebury the position or not displacement velocity change velocity and so on down the line so of course for position doesn't depend on the framer not yesterday was about 15 seconds of play quickly and . 0 For this 1 we have roughly Us 50 50 Split keep that in mind close it now displacement yesterday Robert asking yes and the head the frame no means it depends on the frame egg any of you answered backwards for the 1st wonderful ideas floated otherwise Brit I just means you think it is independent of the frame by no means using it depends which frame it said so That's why were still kind of 50 50 And just saying now renewable city business It is it In the end of frame that would be a yes there's a depend on the frame that would be enough
Where is better I would like to point out the example adjusted with the airplane was specifically So just letting you know B is the correct answer their analysis you change in velocity and this 1 we saw was independent so Eddie is correct that the change in velocity we saw hours in the What about the acceleration quite 50 50 not quite as overwhelming as the others a leaning toward independence Let's do and what by tying here is the time it took the event to occur so in this case it might be the time it took for the chance to go from meter my friend Mary overwhelmingly in favor of independence and Final 1 Is whether not interactive workers so they write Throw it that could interact and throwing became my friend chat about Qatar's that's an interactive so does the person on the ground and in the plane agreed if 2 things in Arak I remember we're assuming invisible jet You go back to see inside and for this 1 Again slightly overwhelmingly in favor of outlets like The actual answers for ones and Rad these are independent of the frame Depend On the frame and this was actually pretty much where we started the Class a few weeks ago And think about if I have my ruler and my organs system right here measuring positions and will mean I Oh you were at 0 0 now you minus 10 but And you had yeah Frame of reference sitting there like 9 0 0 And that 0 Notice from a displaced when you you stated 0 So displays was 0 I said you went from 0 to minus 10 EUR displays of miners disagree position worried disagree displacement organ a disagree on velocity once you get up to the level of change in velocity airplane example shows you now we started range and acceleration of the change of velocity over time interval and as yours and we all have the same plot Now if We do special relativity view move fast enough in this part not true Right time does matter but were not doing special relativity at our level speeds at our world might locking your clock the same so if you start your clock mine and I over here and I said And that you back That we agree on the time Levi said you just what backwards 10 meters like no so we agree on the time it we agree the change in velocity and the time now tells as we have to bring the acceleration right divide to numbers that are the same new divide Members of the same unless 1 of us like ejaculator wrong we the same answer so we agree on acceleration weird re-entered the velocity we agree on time and the final we have to We we agree and interactive assesses like what to and Brother can a doesn't matter by Throughout while moving a bike trail I'm standing still You and I will say I through this camp by taxes but again we both said Carter So this Tells us that in some sense these are the 2 things that need to be connected from a physics for might not interactions of velocity because it 1 doesn't depend on the frame and 1 does how you connect Right now I'm not noticed let's Let's go back Airplane noticed in both cases Now In both cases we get a positive 5 meters per 2nd even throwing again backers of the plane is moving that way It off Trust me you go through every combination and want you subtract the 2 velocities because the only difference between you and me is a constant velocity that will always attract out It was left will be the same Yet For the interaction there Right A lot of ways If ever Whether or not at all That's all Acosta Molossidae there moving at a 145 meters per 2nd the play never changes be being there never has Interaction between the plane and the people to get the people or you fly out the back end Make sense a modem or that yes Yes Look at Back If there's no air resistance to that adds interactions that changes things right once theirs Air resistance that the forest by trying throw the plane back and forth The for the can interact with would away But they were doing that in a vacuum will disrupt back-and-forth perfectly fine World War Brown I know you have to keep in mind would we talk about interaction Emerging velocity from 2 different frames we're talking about being allowed to see every is not a physical line site blocking you know I think about that way physics frames are always completely transparent and you can see through everything that's that The weird thing about physics frames of reference so young personally underground with Look we would describe it as a velocity at an angle back-and-forth would be the velocities but the changes in velocities Robbie whatever they are other questions So we We're until back to again writers New Seguin a lot later on but we get V central piece really of physics 3 interactions cause accelerations and we now then turned this into physics language and we call interactions forces so Forces cause acceleration but I really encourage you to really keep in mind the equivalence between the word for and interact and force it is the strict physics word we like to use a contemporary modern physics we acted on use much we had to use the word interaction I find interaction As a much more intuitively useful work because we can think of forces as literally the visible Things we could see the pushes and pulls interact the much more obvious because if I use the word interaction even if you know nothing about friction as of course you could tell that the book is interacting with the table right think contact with that something going on there is an interaction here That I have to understand What object rooms Vieira you interact with the air and you have to decide whether or not a resistance is small enough that I could ignore it And that I can ignore that force interaction or do I take it into account and that's why The into intuition point of view I really prefer the word interactions the strict physics word we use for that is force any questions on that So we see our 1st what I would call intuition problem The egg goes back to what I less to before Friction exists A resistance exist gravity really exist was lots of interact and you don't city and they are and they do Class changes in velocity or acceleration so you have to keep that in mind Not to understand forces We really end up defining using 3 laws and the use of new and 3 lots were worried firm somewhat conceptually today and I will get to operate there will add in some good demos on Wednesday to deal with some of them again
And then we really started problems with next week so let's ask ourselves Another quicker question Talkers won over with your neighbor could you do Never pictured a little bit but that we like them from about a drive for you right You have your form Is driving that where the ball on the ground and you make a sudden right Charred case You go that way and the question is does the bodice stay place were talking about you in the car you're watching the ball back somewhat outside there's the ball and rolled to the right in the car the left in the car Forward backward urges hang out in place that's what I'm asking with this question can so looking from above that the picture you want a hat I was soon So Jang 8 Ted Mora seconds 5 4 3 8 2 move wine But see where we are At Mostly by going to the laugh and White is a go to the left you wanna say why goes to the left Yes for what better write it off the ball was to just keep moving forward because There is no For some the ball as the car goes to the right the Bocuse moving forward which look to you like it's going to the left and this does question earlier by the interact with the airplane to rank warned the human mind and this is what we call the difference between an inertial and not inertial reference frame so when our Schulte means constant velocity we will talk about not inertial reference frames these are accelerating we'll do much would The blast doors are ones in which an object was suddenly appeared on new even others force on it because it actually going straight and you're the 1 that's accelerating and so when you feel an acceleration in your car when you speed up in the city it's too bad because until something interact with you know last week at the gas pedal the wheels interact with the road that accelerates the park but unless there's a seat You job get accelerator and that is why you wear a seatbelt withdrew the car suddenly stops what you do you keep on that windshield unless something staff you'd rather have the seat belt stop you than the windshield That's just a general rule of physics you experience this but what makes any amusement park ride on In that they put it in and that Herschel reference Frank right you're a rollercoaster local the local loop delivers an accelerated it makes you feel like you're going after him you're the 1 where the room spin the floor drops out you don't fall down you don't fall down during a nun inertial reference frame your spinning around in a circle so Most amusement park rides to me are based on that but As basically the 1st you stay in uniform motion which might be 0 velocity to remind unless you interact with something and the first-floor basically defines the fact that these sort of frames exist so you very rarely use the 1st lot actually the solve a problem but it's much more the definition the starting point of the definition for forces it credible Because the lets you keep mind the difference between these 2 types of frames a reference motion so you are not allowed to use the 3 laws if you're in an accelerating reference frame that Basically all upset Better questions on that So The secular law we already mentioned but will now make it mathematical the set what was that the network total force is equal to mass times the network total acceleration introduce the mask that There really 3 ways the think about mass this month that's what we call the inertial maps which is You're resistance to acceleration your mask tells you forgiven for how they will your acceleration be to little Mass get a big acceleration of a big nasty really resist accelerations resist forces to use small acceleration in chemistry and basically that you have and later on will see it sets the level of gravity as a force turned that they have to be true Where the amazing things about nature to the best of our ability to measure the fingers of gravity is of course and much that you have is also thing that resists acceleration of 1 concept mass that has 3 different definitions Notice and this is the key thing amid a rewrite as was ever again At a news colors now F Equals and times acceleration And this table signed means cause not the same thing White as the definition of acceleration Isn't it is acceleration is what you did not by Friday but even Remer fancy the derivatives that is the definition of acceleration that is what it is Forces we will find out the different forces we will find spring forces we will find gravity forces we will find friction we will find pushes and pulls they will all have their own definition those will be the definition of forces the amazing thing about the world is if you add up all of these You take look at the mass they will be the same numerically as all of these which you are defined by completely different way We use forces cause acceleration they're not the same thing as acceleration that is very critical remove on the biggest mistake was to make that out at all but of course the acceleration set the the mass times of acceleration accelerates the most out of the equation the can't allow a mute the problem on you need to keep this in mind notice with other places We can get acceleration from if things are constant acceleration for instance we have final squared equals not squared plus 2 88 . doubt that the other equation I have to speak as a review for Friday right don't forget this nose is a way to to find the acceleration once you've found it By Its definition you can use it to tell things about the forces There were in a close here where What I crawled into a shin problem number today Forests is a actor I were talking net force so let's forget the quiz
That we had before the class and is revealed a couple of these as we finish up so there is realized what examples of it This was just a point out there some common things we say fun as part of new loss They really are In the big 1 that summary which was what goes up must come down just do the goes out It doesn't have to come down rocket made it to the room they don't come back down there I was very proud of you number 2 is a very classic problem I can tell you right now so version of this will show up on a fast in this class Not this Friday from forces this is a classic Milan's soared why I haven't mentioned it yet but 2 things always interact with an equal and opposite force and the magnitude here It is 10 and most of you got that the time quake Many of you This latest shows of the exam search it doesn't mind there was the 1 that most related to what we do is dead it I object is moving past you in a straight line because speed walking you conclude I guess we went over this right to be getting their ears No constant forcing direction emotions constant speed in a straight line there is no match for that 3rd answer here where you can I conclude that there are no forces acting on it because the net for And 2 reactors in opposite directions of the same magnitude to cancel will do sold back is the final piece of the big intuition problem were adding that there's been an actor's cancel survived remember what for Ford start Wednesday with a problem I posted today obviously would get to red
Demos Ahmad finish the conceptual introduction U.N
Bombe
Cocktailparty-Effekt
Computeranimation
Woche
Transistor
Fahrgeschwindigkeit
Abwrackwerft
Buckelschweißen
Array
Längenmessung
Kopfstütze
Bogenentladung
Übungsmunition
Tinte
Satzspiegel
Römischer Kalender
Boeing 757
Reihenschlussmaschine
Drosselklappe
Takelage
FIR
Mitsubishi Colt
Atmosphäre
Ruderboot
Kraftfahrzeugexport
Blechdose
Erdefunkstelle
Auslenkung
Koffer
Nanometerbereich
Spiegelobjektiv
Kopfstütze
Spiel <Technik>
Gasturbine
VW Beetle
Stunde
Satzspiegel
Beschleunigung
Tag
Telefon
Stack <Brennstoffzelle>
Druckkraft
Reif
Schiffsklassifikation
Gleichstrom
Rundstahlkette
Innere Reibung
Mikrowelle
Ersatzteil
Initiator <Steuerungstechnik>
Mittwoch
Messung
Magnetisches Dipolmoment
Zahnradbahn
Energiequelle
Parallelschaltung
Gagat
Akustische Mikroskopie
Cocktailparty-Effekt
Sägeblatt
Beschleunigung
Leitungstheorie
Computeranimation
Stack <Brennstoffzelle>
Schlauchkupplung
Bildfrequenz
Fahrgeschwindigkeit
Bildfrequenz
Angeregtes Atom
Atmosphäre
Druckfeld
Jahr
Absolute Datierung
Direkte Messung
Rotierender Radiotransient
Venom <Flugzeug>
Drosselklappe
Atmosphäre
Bergmann
Erdefunkstelle
Fahrgeschwindigkeit
Hobel
Auslenkung
Antiteilchen
Nanometerbereich
Be-Stern
Holzschliff
Phototechnik
Kopfstütze
Spiel <Technik>
Satzspiegel
Blechdose
Stack <Brennstoffzelle>
Strahlungsnebel
Druckkraft
Band <Textilien>
Schiffsklassifikation
Nassdampfturbine
Gleichstrom
Innere Reibung
Zylinderkopf
Hubraum
Ersatzteil
Initiator <Steuerungstechnik>
Erder
Greiffinger
Gesteinsabbau
Fahrzeugsitz
Anzeige <Technik>
Intervall
Gagat
Kugelblitz
Energieniveau
Sägeblatt
Samstag
Lenkrad
Satz <Drucktechnik>
Schwächung
Beschleunigung
Leitungstheorie
Computeranimation
Woche
Bett
Windschutzscheibe
Pager
Bildfrequenz
Messschieber
Monat
Rad
Fahrgeschwindigkeit
Kit-Car
Maske <Halbleitertechnologie>
Buckelschweißen
Sicherheitsgurt
Gewicht
Kaltumformen
Schaltelement
Bildfrequenz
Gedeckter Güterwagen
Telefonleitung
Übungsmunition
Drehen
Satzspiegel
Atmosphäre
Vakuumphysik
Lineal
Frequenzumrichter
Anstellwinkel
Drosselklappe
Masse <Physik>
Kraftfahrzeugexport
Bergmann
Gesenkschmieden
Erdefunkstelle
Fahrgeschwindigkeit
Auslenkung
Hobel
Steckkarte
Zeitmesser
Nanometerbereich
Tretboot
Gasturbine
Stunde
Spiel <Technik>
Beschleunigung
Kugelblitz
Stoffvereinigen
Gas
Druckkraft
Nivellierlatte
Schiffsklassifikation
Steckdose
Wasserwiderstand
Innere Reibung
Gummifeder
Hubraum
Buntheit
Ersatzteil
Mittwoch
Sonnenstrahlung
Spin
Juni
Druckkraft
Kernreaktor
Computeranimation
Schlauchkupplung
Schiffsklassifikation
Raketentriebwerk
Herbst
Gleichstrom
Scheinbare Helligkeit
Ersatzteil
Vorlesung/Konferenz
Direkte Messung
Mittwoch
Leistungsanpassung

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Formale Metadaten

Titel Basic Physics Lecture 10
Teil 10
Anzahl der Teile 26
Autor Dennin, Michael
Lizenz CC-Namensnennung - Weitergabe unter gleichen Bedingungen 3.0 Unported:
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DOI 10.5446/12921
Herausgeber University of California Irvine (UCI)
Erscheinungsjahr 2013
Sprache Englisch

Technische Metadaten

Dauer 42:26

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Fachgebiet Physik

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