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Basic Physics Lecture 16

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Let's try to get started hard on the same day exactly this time the blast happened last year and the big question is OK we just and forces and I realize that goes
Kind quick that 1st reinforces but likely this week with static equilibrium we see all the same forces again so that will help would assume the different context but Figuring out all the forces of the object and asking yourself How do I know what I actually found all of that is a very reasonable question 1 big challenges so here is the 1 PowerPoint slide on good way now You try this a little bit hopefully this will help you go back and do more of them and the ideas the following the 1st Maine step is to identify the object Roddick's of interest so Yeah we had this problem There are 2 objects potentially reduce sorrow and depending on the question we might only need to worry about 1 of Or we might only be asked What is this 1 billion but we realized with attached to this 1 day and their quest will need to about what Now you take each object 1 at a time mn identified its interaction End We only really have things and you just check each of these Carefully you all have found all the forces now that brings in a week so your doctor about that but you check for weight Work You checked as she and you have then check contact with every object abiding contact with obviously Yes the look using their purchases they're not but it'll state fertilizer Saying coefficient of friction And then you check for that string Roper bar that Mike connected to something and then you check for those things are really normal forces but we column pushing or pulling and that happens you think of that separately because here right it's sitting on the table and so we have the normal force friction the problems said somebody is pushing on it you know Often draw that person the problems are not feed the object pushing and that's why we kind The figures pushes and pulls the separately Citing questions on that so this slide posted And I recommend it as kind of a helpful way but it raises the question to predict the question for next week but I know found all the talk but you have to do step 1 identify all the forces which is why it's time leader review it And this is the big 1 identify where they act now there's a few but yet to keep track of Wait is always at the center of mass which for the objects we look at will be at the center of the object survivor being at the length L weight Exit point over 2 If I have you know a disk that uniform the weight acts At the center of their friendship is being a rope being or something like that but it acts along the road Now if it on pulling up occasionally have metal rods push on the object And then down and then refer to the normal forces act were ever year in contact so it might be missing contact with the wall than the normal force and friction and will act at that and I will see that our free body diagram And so those are the main 3 forces we get now course you could have things sitting on it so here there would be a normal force from its said in an interacting you have a person on it and you have to be told where they're pushing and the you know where The pushing forces questions on that The 3rd game of quiz but a club for Is of course the right-hand rule and I agree that some practice but we got 3 of 4 examples I'll be doing between today and Friday and will be given the right hand will each time the hopefully between me doing that yo yo get to see how that goes I am willing to to summit suggested when I do I do it like you face in the board figures my hand works and I could do that I'm summit escalated dot diagrams now I'm incapable of very very bad at that but like at the diagrams of the book they're better doctor The best with the clicker Christ and by Agatha should ask any questions on any that stuff way Ghaor flickers out yes but is like Ike moved down a lot or have a like this so this is a warm-up quest to remind ourselves about George can be 0 force acts At the axis of rotation the force acts parallel to the mama are the 4th act perpendicular to moment both a and B or both we have a majority getting a correct Both of attacks at the axis were trying today Right to act at taxes or Our 0 by definition and I can't make a rotate about the door you push on the here you can't make the door rotate and the other 1 is if we sat parallel To the moment arm so keep in mind that my access heroes are here's my might have of course that is that direction which is parallel to the moment arm it will rotate right that's just pushing it at the edge of the door might push on my head to the door is not a right away I have ever component that Perpendicular vests or that will make it rotate so the answer This is D both a now they're the 3rd 1 was the 3rd way have no talk no force right that's kind of the trivial way for Questions on that so let's let's look at our 1st of our problems This is the 1 that was basically a beyond our Lanquist but it's worth going through and step by step The idea there is we have a being An interest in and to support Our call it a and B 8 5 meters long and it has a mass of 10 kilograms so it Wait the 100 new and 10 kilograms times Jeter meters per 2nd square that MG now a few things to start getting used to static equilibrium is the idea of resting on a support so it's just sitting there forces being attached to something
Right if I'm just Iran's and something What is the only way the normal force point Up in this case So there is no other way I really move the being up and so At normal 8 0 0 Would mean I lose contact with the support and has to be up there vomit catch something right if I physically balls something here and now the force at this point Kimbrough go any direction And I literally means any direction got up down left right Arad an angle right so the bulk could make a force that way to make a force that way To make a force that way To make a force that way So physically attacked uniting get a force in any direction and will see a problem like that A little bit later But that's a key thing to keep in mind as we got it is the problem Any questions on that setting up stage that I guess I could set horizontal being but evidently slanted will tell you Right and slanted and Asia's rest because that attaches to do what I just slide off so that I could even be physically possible if it there's ever As always in the problems we try our best to make the English clear we occasionally fail so that the task and you're not sure you how could be horizontal could stretch Still You know ask those sort of things we were willing to clarify So let Look at these solutions So read-write here Here's my being My and my being But and there is my 5 meters and here's my weight down now the 1st thing organ and it is dry what we call a extended free body diagram Animator X X Y and Now we use our right and rolled to make a right hand foreign assistance by figures go with acts curl and wife so my point out so Out of the board is my positively axes A new notation and this means out This is arrow coming at you you just see the point of I draw best in physics at means didn't Bezier abroad away from mutual feathers on me and that was the convention of I'd rather see you like this you know most of the time we know that that means out but Optical loosens take that look like it's going or you know you could have weird visionary things going on so This is invented this for out in the fur and we draw free body diagram we have 3 4 says weight which is in the middle said may have meters from either end and are call F a N f V for the a and B axis And now we write our forces in the x direction while there's none of those so that Easy they are forests in the wider accident while that FAA plus As B minus W equal 0 we 1 a flying these 2 forces so that said to 1 nuns lease 1 more equation if you recall this was a hundred new and it was our mass times gravity because we know what weight now here's what I want you to do I call this point a this point me and this point state and you're sitting over there Write down torque equation for talks about point So desperate that got you're writing Now you let your sorry You during B and then you guys in the City of God and do that but see everybody to write down tort equation But To remind all Wang is 5 meters The trip Upon them I want you define the sum of the torch around Point which is right in the middle ataraxis you're acts that we beat out yet So you guys The axes at point saying year lasted about rotating about 40 Everybody in the middle You have it acts as a point being Right in the center and you're writing Wadsworth wrote About the the center and everybody in there You have an axis at point C and you're writing toward rotating around . se Aug day But bloody time right now let me ask you this further matter whether you're a beer comedy toward do you have in your equations while 2 or 3 How may have what they know bristle had 1 comedy had to The breadth of the original comedy of Is not really want to be 0 If you're planning 1 being 0 OK having 3 right We use it count when the 0 Hideo state now derive a representative from Group 8 to tell me they're Georgia equation about thoroughbreds also yes After the or what None of this is toward around an axis at For a day Yet not the due to the force point because that doesn't mean it likely the access anyway right so this forest while I'm taking this as my access anyone wanting to me some torts about that was dipped group above smarter urban middle all sometimes forgotten anybody in the middle
What a give me their charter grated or recover the same level of all the crew bad there's more argue somebody must have gotten it yes Make it a shot Look at it Up to But we don't know how many were the forces yet right Necessarily You have 1 from each side what are they Story of 1 from man and 1 from ever be cut away the tort The 1st times y If I got Attacks over Again with the authority to those cases they said 2 . 5 meters And that give me directions for to What I did As they rotate that way at And there's gotta put it down this way not put it up that way which way is the 1st run Yes that's how strong clockwise so positive or negative The hours that negative look at them that have been must be positive actually so Group D E due date Or he did at some of you help object Bruce C. last 2 Let's let's get about the same size which may cause which made negative Which when your father which you want negative or butter MBE now I mean . se sorry But they say What are they The 0 Texas OK so you actually slightly differently you're and is actually RFW I'm assuming OK so let me change that Excellent and so we had a 2 . 5 times ever W 5 times as and their which would make positive which is negative At OK So again as in this case That may is actually be negative for the going the clockwise that notice When there's just job on a again backers doesn't matter Look at the same answer no I run into trouble you start getting 3 or more now anyone back here Group Now want Come on you like that to reduce out there I would suggest copying 1 from . se and changing some letters a that sound like a good idea what everyone is organ really drawer A About point out what direction is ever W. would be about when a positive or negative negative and what are is it The Gerber . 5 m what about But Wenger may be positive and what are 5 now I know we made that very painful but But The there this is the heart of all of ongoing had to really That the forcibly at an angle And I take a perpendicular component data Archives and data But this is it and now you have to recognize new were not allowed to use all 3 of these They look different but they're not abided this 1 what it tells me as ever be as bad FW over to if I take this 1 that tells me and be equals F M I take this 1 that tells me that egg equals FW over to enter by combining with this equation here You'll see that All of them right might put at tables been year this tells me FA Because as being a post that W over When I've added any of those it so you are all always allow in any given problem to use 1 toward equation drew not trying Used to Earth rear for you just get redundant information it won't help you now son finds it will appear that help you figure sometimes known as well as given the problem when of course is to gin up 1 of these 3 you know the way knew right away I suppose a question just ask you what is Went equation would've been the best is right at the beginning Point said because The only unknown is whether I wouldn't even if needed either might force equation there are problems where I correctly that torque equations Woods is due to be answer right away Because I can eliminate notice I eliminate any force from the equation that are equal 0 And so by making a point and Texas where I have unknown forces they don't show up in the equation and if I have an unknown forces that I don't need the hose I can't solve the problem in 1 step So this was the problems really is a great example that's why I did it so slowly the highlight a number of key Points and doing all these static equilibrium no matter how complicated it is it is worth Thinking a little bit about which point to do toward about and sometimes they doing that before you write down the force equation for The Ajax There is always a convention and physics you could do it the other way as long as you're consistent and the entire problem your get it right But in physics it is considered the convention that counterclockwise is positive because you're going from the X to the Y axis in a standard what we call writing and important system it is nothing and nothing understand there It is just a convention we had a a lot and we just don't like the direction Clark Here That's about the best I can come up with Any other questions on this 1 Now let's go Tour next problem now again
As I was Saying earlier To maximize your experience in discuss that tomorrow you won't be as prepared as possible so For tomorrow there a 1 master in physics problem to go through it should take you according to master in physics about 15 to 20 minutes which is a lot of things to put front but it'll take you through all these right-handed things getting your trucks The right direction and then there is 1 of requested problem that is a lot like this freedom work through and think about and then they'll be the 1 to do tomorrow if you do that Pratt tomorrow will go much better now as I said The only real thing I kind of add those forces that I'll be at an angle this is of being it supported by Bolton the wall that a wire that forms of 30 degree angle so dry in the free body diagram are we to ask yourselves or dead But you can see things 1 is the direction of this forest we set is always longer wire so it's airing of data we haven't weight which is always in the middle And then the bolt can be in any direction and the way we almost always do that is what we set out components with throughout the XOY confronted many reactor They are reliever 1 word to describe the relation between them Yet they are perpendicular that is 1 word But they are independent of each other So If we have an unknown direction the way the handle that is to immediately turn it Intuit's X and Y component deal go separately now we haven't issue which direction to drop Now why do you think I drew the x component to the right The key is Not We know we want static equilibrium so be true about the sum of our Forces 0 do we have any other ex forces in this problem Yes which what That's a little tricky which does the wake give us any force in the extra direction now it A wire appalling and the direction which way Laughter right left so we want any chance of canceling a which waiters the wall have pushed right so we're pretty confident Now I drew a wide array A confident that has to be up Of What ever lighter Ray way down and take up so do I really know which needs more help Now Joke This is a a and you'll see as solve a problem and I could do I couldn't play The laugh and I still get the right and you'll see how but with the wider Rexon I really don't know which way to go I take it up just because I was positive it makes life easier Warsaw from there and see what happens Any questions on that now let's go clicker question for this problem And that help you the glitter question I will redraw the diagram As the top the list they cook cheese Critical that have wife and that effects So with this diagram Which of these equations for tort is valid But 0 8 It showed off tried again area so I'm going give me a bat measuring Davila lager this want to talk to the person that you really right at your equations for talks and see which of these is valid tighter we did before I wrote here in the sector now having you do all of together just it out When I say axes rotation on the left that's the last that's the right Not sure that The archery tour now was interesting Most of the year the majority of them are going with Only 1 of the 2 air beat some of you went with about another duet with above let's see if if you have a good reason why discusses 1 carefully trying to brother Ron and let's vote again that simply any ships elects like the people picking be back events go about
Will be only air sticking to their guns So I am really curious someone could only had what what what did you not like about B What why did you like F Y your charter equation I'm doing torts around 4 o'clock The Israeli because plays 40 per cent used of very strong so there's something to be out as it were fundamentally understanding so I need to know why you picked it so we can correct the issue what why I did people not who didn't like we wanted they not like about FYB network On Object Actually it it's a signed so as were going this way for are so hours like of news show you hides behind my back are is like that's right and desire So my thumb is now in the board which is negative Yes you're ladder that you get your fingers always point where are so that keeping of glad that came up object so that's what fingers door complain either way so your 1st choice As my go this way this way you're Seguin choices do your upper down depending which way after excellent now there were problems with that I saw another man was another question Other problems with with being correct Now s calm yum Set up 1 right so this right so You have to look at but the effort of wife of actor and I understand that would throw off a little bit levels of course is that the force the bowl of the previous life I was a little more clear I call the B & B Y B act but I realized it might Question said at some wife so I was consist of the questions or any other potential issues Exactly how how would you have an axis of rotation here has been attacked a wall there Will think about it because the kind of attacks to wire here so one-way could fail This would off a wall swirling around the wire that 1 with think about it but even more importantly the axis of rotation is an abstract idea you're allowed to Any arbitrary point in the object and saying it I held at that point how would it rotate around that and so I couldn't take matters a rotation like right here and I would use all 3 forces and their computer talk we usually don't do that because when advantage of picking the actors rotation at a critical point where there is already a force you get what You get rid of that force set forth doesn't show up so the reason we picked this place the left or the right or possibly the center I do that in this case is Those of the 3 places were those of force and not as it my question why what is intentional wife Where would you A or would you pick me to do toward family would a request as was the the Sentinel wire break his or your hand up let's try that how many people would Now why would you put their leader solve a problem now Juno and Yes do know that don't so I sovereignty collecting cancel out the yells knows that it whose again be aware and his wife doing a lot of hidden variables in this case Elwood just cancel so I wouldn't have to tell you how long the remote Would drop out of the problem asked for just a white Component of the force on the ball then you would do that and that's why Getting comfortable with moving your axes around is helpful now it might take theirs and asked for the tension still solve the problem yes you would use more equations to do so There's not a wall on taxes the but there is often a better access to pay them if I go back we'll see this question is asking for the force on the ball so we won both component forces of actor we both the magnitude of the direction give me the answer is either components The actor white and voted for the magnitude and direction that's fine but this was a problem exam alone you will need to tell me the whole Fort Belvoir using components for a magnitude and direction it will I get a solution for this so we had our means at our forces Warwick all that F. BY will go back to the boat notation s of the Act we at 10 with Data I will have W we maker X and Y quarantine system so now we will leave forces in the Directions and that Simitis attention cosigned 30 remembered and take your components for us at be axed equal 0 will be our forces and the wider region so I call that BY positive Selover will have the chance So that the component of the tension in the wider action and wait as our negative force and we need artwork and I'm gonna do it about point a Even tho in this case I'm looking for the ball Force when I notice is if I don't have the tension I really can never get The Act component of the ball force so you know there's a toward equation that would give me this right away I was still need uses equation this offer that for that to suffer that if I get attention this equation gives me f both acts in this equation gives me ever But why it a little simpler Thinking that way so I do my torque equations which was yet engine size of 30 Times the length of rod minors Wait times over to equal 0 my legs canceled and if I like my numbers My attention turns out to be 50 new things and then I can just plug that end to each of these equations And I'll get bowl X people's 43 . 3 new friends as what while beat woes 25 new and that in turn that into a magnitude and direction or leave it like that now here is the final key point they're supposed to have this 1 came out to be negative 25 new and what does that mean that I do a problem wrong or does it mean something else what is it me It just means of the force is down to the negative direction is down right I doubt that it was up when I wasn't sure I don't know for for sure I saw the static equilibrium Monaghan name and that means you had the direction wrong to begin with When you need to change that problem is very similar to the 3 questions and then the wondering tomorrow so users will you prepare for discussion
Rotationszustand
Magnetisches Dipolmoment
Rutsche
Computeranimation
Woche
Rotationszustand
Seil
Druckkraft
Prozessleittechnik
Gewicht
Kaltumformen
Seil
Elektronisches Bauelement
Schaltelement
Urkilogramm
Angeregtes Atom
Satzspiegel
Knüppel <Halbzeug>
Bestrahlungsstärke
Jahr
A6M Zero-Sen
Lineal
Pfadfinder <Flugzeug>
Schaltelement
Synthesizer
Gewicht
Masse <Physik>
Stringtheorie
Gesenkschmieden
Regelstab
Antiteilchen
Nanometerbereich
Feldeffekttransistor
Blasenkammer
Spiel <Technik>
Innere Reibung
Zugangsnetz
Parallelschaltung
Metallschicht
Tag
Stringtheorie
Rauschzahl
Druckkraft
Erder
Thermalisierung
Gleichstrom
Innere Reibung
Zylinderkopf
Masse <Physik>
Holzfaserplatte
Gewicht
Greiffinger
Hyperbelnavigation
Masse <Physik>
Schlauch
Kugelblitz
Konfektionsgröße
Lötlampe
Feder
Energieniveau
Postkutsche
Antiteilchen
Nanometerbereich
Feldeffekttransistor
Computeranimation
Avro Arrow
Kopfstütze
Kompressibilität
Passfeder
Stunde
Schall
Zugangsnetz
Elektronen-Energieverlustspektroskopie
Elektronisches Bauelement
Gruppenlaufzeit
Tag
Schaltelement
Rauschzahl
Minute
Xerographie
Molekularstrahlepitaxie
Übungsmunition
Druckkraft
Pelz
Thermalisierung
Angeregtes Atom
Gleichstrom
Römischer Kalender
Jahr
Absolute Datierung
Masse <Physik>
Anstellwinkel
Synthesizer
Holzfaserplatte
Rotationszustand
Gewicht
Greiffinger
Drehen
Kugelblitz
Regelstab
Energieniveau
Cocktailparty-Effekt
Antiteilchen
Satz <Drucktechnik>
Minute
Feldeffekttransistor
Kernreaktor
Computeranimation
Juni
Rotationszustand
Boot
Passfeder
Abwrackwerft
Klangeffekt
Array
Stunde
Zugangsnetz
Schusswaffe
Kaltumformen
Relativistische Mechanik
Eisendraht
Elektronen-Energieverlustspektroskopie
Elektronisches Bauelement
Proof <Graphische Technik>
Übungsmunition
Druckkraft
Thermalisierung
Weiß
Eisendraht
Gleichstrom
Atmosphäre
Schiff
Hubraum
Lastkraftwagen
Kritische Temperatur
Scheinbare Helligkeit
Jahr
Anstellwinkel
Masse <Physik>
Anstellwinkel
Synthesizer
Holzfaserplatte

Metadaten

Formale Metadaten

Titel Basic Physics Lecture 16
Teil 16
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 10.5446/12927
Herausgeber University of California Irvine (UCI)
Erscheinungsjahr 2013
Sprache Englisch

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Fachgebiet Physik

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