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Basic Physics Lecture 25

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So let's return just quickly found to a few few issues from the last example problem we did just a highlight where we're going I'm not gonna resolve the problem by any means but I do wonder like that the collision right we had a ball that
Where some velocity not that everyone defined there was the block a word with velocity 0 this is our initial and at the end of their combined in final And has Net velocity be final Where when I get the problem i.e. I apologize I do not actually draw this picture and I had a few questions afterward so I want to make sure we got the picture drawn because it's a collision Weaken served momentum So it where we looked at the initial momentum We had the mass of the bullet I was really not that's the momentum of the bullet was 0 That was the momentum of the block of away because it was not moving at art Final momentum it was a single object so that a combined mass of the 2 times velocity final so we went from 2 objects to 1 object so if we have a collision were things step that have met You I a 1 object anyone keep track of of that if we have an explosion or launching a rocket will do a couple of us today there we go the other way We start with 1 object And we end up with jails The other type of collision As returned things that And they bounce off each other and they don't stack so we start with 2 and we end up with 2 So I'm odd 3 basic collisions Or explosions are 2 objects going to 1 object when that happens you'll have an inelastic collisions we will lose kinetic energy we will talk about that we will have 1 abject going to chew abject this work we refer to as an explosion and the final 1 as are 2 objects going to 2 objects and this would either be elastic or inelastic and so we defined elastic Eliza's conserving mechanical energy almost all the time The elastic versus elastic is a question of whether or not the changing kinetic energy is 0 or whether it's not 0 Now there are a couple way things you wanna pay attention to So if 2 objects step but it's always in Alaska and you would typically did you As it is momentum conservation the Finder velocities and that if you wanted the completed the energy lost again key mind this is a strange phrases as why putting Annan quotes Write the energy losses that really lost the goes into other types of energy is almost always kinetic energy lost and I don't know why we don't to say that but I'm using the common phrase that everybody else uses the fossil energy lost so as not change of energy It is if you figure energy decreases that will be a positive energy lost so it's kind of a weird Think objected so it's on then the initial minus the final because it's how much you last nite with the change what But you would take these velocities and just plug into whatever you had initially and subtract whatever you have again and often at the end it might be some object that combine this is just an example it's not a formula You might have an initial single objects of his 1 object Moving sticking and both together you might add to objects at the beginning that you have 1 that can be read and 1 B I squared plus one-half and to be too I square annuus subtract whatever you haven't yet Many questions on that Now if you have say a more common ones 2 objects mess a mess be Baker maybe they bounce off each other so this is my before And is my after matters kind of true possibilities the problem may tell you it is elastic or inelastic
And then you now Kinetic energies server not Prices in what it might not say Every vote But it might ask you visit elastic for how much energy is lost a danger there too often students not just see to lives bounce in off But soon with the last solved the problem using that as in June soon force it to be a lasted you get an energy losses 0 When in fact it was an elastic and energy was lost and that the problem wrong so if they're asking you visit elastic parameters lost you cannot assume until last that means there must be another information but only use that momentum is conserved and then you find these and do what we did before and then compute you're changing kinetic energy and using that you will give your answer either at 0 in which case elastic cords not 0 With his energy is lost So survivors of the scenarios in collisions a going through some of us today Questions on that Yes say So I guess I have a question might be on exam at the mall work every day I do today might be on Friday's exam because is also was included on workers do when said everything on Wednesday This Estrada revealed showpiece about But in the reviews Chapter 7 8 and I'd might Friday everything else is for the final This leads us to an easy warm up Iike collector question so this referring to be blocked problem day so this is the ball and hitting the block the 2 them sticking together and then moving the question is how would you find the kinetic energy loss in this collision there is no energy last desires concerned subtract the final measure kinetic energy trying the force from the imposing computer where the problem cannot be done excellent 70 per cent of you got right this is exactly what you did When you have a collision virtually sticky notes last that finding the kinetic energy loss As a matter of sovereign wealth velocities would you can do user momentum conservation you don't like it in for kinetic energy reform energy after and what and how much was lost so it's fairly straightforward outlets will take a site where we get a bunch of collisions the other thing that can happen right as I have an explosion and a standard sort of explosion is a rocket ship Lodging and then you want the rocket ship and it goes out And that rolls down and the before situation is you have the mass of the rocket plus the mass of the fuel and typically you have a velocity was 0 just sitting there so you're initial momentum is 0 after you have the amassed the rocket times its velocity and the mass of the fuel plant that's velocity because their separate and so we can say pianist initial equal 0 Equals final which is the mass of the rocket science allows Iraq it 1st mass the fuel and velocity of the fuel so we get the fact that They must move in opposite directions and attending only massive the fuel relative to the rocket and the speed of the fuel that is the speed of the rocket pretty straightforward may have noticed this is a simplified version Because an atypical launch of a rocket Among going vertical What is the 1 other thing I do after worry about what else is around Gravity and regulate That sort of Launch instantaneous or does it take time It takes time so There's a lot of fuel Coming out over a finite amount of time so depending on where where are you wanna know the velocity of you wanna know it said here eras there's are rocket again on the ground and then years are rocket Right up in the air and all the fuel is gone a you know how fast it's going right in the absence of gravity you could figure out what the speed of the rocket The U.S. no energy of the rocket and it was growing up in the air for some distance dealt acts and you could figure out the impact of gravity on it and recalculate new speed through 1 of find it at some time between those wrote you really have to worry about things like the impulse being integrated force DT worked out They details so
All are there is other ways you can do it they getting more complicated using find differential equation but if you're basically looking at 2 key incidents or are in luncheon something horizontally were gravity doesn't matter it worked so we can demonstrate this by
User pool rocket which is going to have a lot of air under high pressure There were few . the bottom that their fuel and our rocket will what we already 3 . 2 5 us is that we don't want to administer the announcer Monday in the particularly since the bike behalf but we plan
The threat of photo them with the hottest ever were done all year about mail with what's nice about that as you well know their comply would last you really get to see that but wanted the rotted is just conservation of momentum and 1 of the key things it is right in this case so that rocket has a bunch of Aaron world do it in terms of
Magnitude now right We know they went in opposite directions the speed of the rockets really given by that but as good as it is Often much greater than the mass of the fuel amid the fuel was And I mean there is pretty light in the rock and this is the heaviest of rockets but there's enough plastic here is heavier and so what it really comes down to is the last of the fuel to be quite large and that's why We really pumped up to a high pressure now if you sweat and comedy you've ever done this with water made a water bottle rockets Most people had they been in like girls Scout Voiced doubts purveyors of the things that usually happens there if you did worse doesn't get water borrower go back complaint with water You really increase the mass right of your fuel a fair amount and thing gets a really high launches a ghost Quite well but we cannot so do this Same basic idea horizontally with a cannon OK so of course we have to ask a clicker question about her can just to make sure all the same page So right where we have our cannonball and here we are can and will load are
Up and then will fighters and the question is when you fire Was against their place Does the cancer was backwards against moves forward or will depend on how fast this object is launched when it was forward backward or stays in place to about excellent so they can better move backwards bizarre basic weak oil problem just like with any good pinot still wore Eric Cantor with load of liquid nitrogen
Having prior McCain and there and had his day with their lawyers
Can I I had moved backward and how he thought that was once again
Now we take A heavier cannonball And maybe we use a alone liquid nitrogen At the time That Show me a quick volunteered a hole the back end of my Canon here demand down their the freeze my hand off Both shots she says she pledged to on
Scientists some dramatic a mail about parallel rattle a good measure but there you go again dwellings moves backwards at least I know I will say the best time ever did this have really treated as I got enough liquid nitrogen got that form of the don't like to do this but the top rose
The bottle So when it launched the waters great everywhere chemical energy electric at the Warwick employed at the back but man am not Those of tearing down but still very that the rocket but it's important to look at this in a letter opener detail so if you see the sun a problem you don't make some of the common errors so what I wanted to do here's here's the cannon renders the cannonball let's oppose this whole thing is up 30 degrees from the horizontal I want you to tell me they figure out quickly and piece of paper how you might figure out what the speed of the cannonball it if you know how fast the cannons going backwards Societe how you would figure out how fast the cannonball is Darlene leader throughout best is moving backwards and whether or not there's any problem with that calculation so try that for a few minutes here so Another way me wit you're doing the massive genome Bob the mass of the can Peter during the last velocity the can after a launch backward and at present An explosion but will not mention that nite considered At the time of the explosion to be basically 0 Let me to rest Has anyone come across A problem With this Problem you should have a problem with this problem now values news velocity turns out but there's something else is going on here what direction is the cannonball traveling when the collision is over Up at what 30 races were Nicolas and our what direction as the Canton traveling straight back it in this fairly realistic prompt and here is where we run into trouble they certainly Delta which equals J. which is F. average dealt the city will be 0 in delta T is small enough The problem is when I'm sitting on a rigid surface here With my normal force unless I tell you the actual read Coryell velocity of the cannon at 30 degrees He is you're not a mail solve the problem Because what's happened is by telling you the cannons going horizontally I haven't really made delta T 0 because this Normal kept it from going under the floor so this is 1 of those tricky cases where you have to pay attention to the information that you're giving because it is sometimes done this way in problems where this is really sitting on the floor so even doubt that he is very small it's never exactly 0 And the normal force An act very quickly so you never see the velocity down you only saw the horizontal recourse velocity so from a Ricoh oil problem you could only get the horizontal momentum so let's Do that Re-equip because what happens as I need to worry about XOY right and my initial state Vehicle was there So period Total 8 0 been my final state I had em out the cannon times the last year the cannon and I the cannonball times last weekend But now it my edits why cordon system the velocity the cannonball was that way Yeah I haven't given you the troops Cannon velocity of I just did you that right when I gotta write down my ex and my wife equation in that direction I'm OK I've 0 equals massively Cannon times EX component of loss Jenin plus a massive again a ball times its X component of the y direction I've 0 equals Some unknown number plus mass in the cannonball time was can among the wife and is it best that makes conservation of momentum not useful for this problem even those looks exactly like went so EA that I would have to tell you the Canon Ricoh boils down at 30 degrees with some velocity venue would know that And you'd be OK right Or I tell you something about F and delta T to get dimples and you actually focus just on the cannonball venues As the cannonball Delta T because Delta P the cannonball soap That's where you have to make decisions yes Not because you really you this problem and the information I gave you gives you no information about the vertical recoil the can you Chile of 3 I know things you have that Cannons velocity and the wider accident at the genome balls last in wine in extra so there's really nothing but allows you actually get any further on this problem thereby giving you some information and say about friction or about The normal force in the time of the collision then you could do stuff Then you have things you could work with Bode just this information yeah you're stock And I just kind of warning problem Now very calmly low You might have a slightly different problems You might have been told Where the Canham ball lands In this case And and you might be asked for the extra week Oriole of the Canon now notice You have enough information defined the cannonball Velocity because you do the project motion problem there when I have a cannonball velocity since I have both by definition I could do that problem I now have enough information to go in that direction So there I would use conservation momentum because I am allowed to conserve momentum in just 1 directs an e-mail was in conservative a wide of the normal force or I don't know enough about it I can still find the acts by using conservation movement I know these Get a little tricky and that's why I wonder appoint this out hopefully it Will clarify as you do the problems not confuse questions asked Right so here where you didn't it In this by the cannonball alliance again went 200 meters The same height as the jet was lodged at 30 degrees What was the recoil Blasi the Kennedy that direction then you would use project margin this offer that you used conservation of momentum in the x direction to sell for that
Took so America notice notice the difference here these both announce the gave no other information object and this was unknown because you're really is 0 Is not the actual velocity of the kennel direction after lot it is actually moving down it just gets staff group quickly by the ground so you will bite Only measuring its X component you're missing a piece of information That's why component it what you wanna do they solved worthy Velocity of the cannonball notice if I give you this I can find that I deserve no idea what that it's this is the 1 I can find The bank yes Life While on the right The That way Pretty out of the total 1 side of the triangle and the angle you need 2 sides of the triangle to use trade yesterday Signed his opposite arrived news shows and sign as Jason or no signed up those posed by the jet our partners by staggering 3 sites where On my whereas my trial lottery numbers I No no I'll Shiloh I gave you the angle that I mean so silly That really work yeah I guess that really works then eh now I still I realize that really works I I thought I cleverly came up with an example that would confuse your now I'm thoroughly confused you good weather and a quarter lengths Aaron said will you have 3 days to recover from my confusion but however I would like to say momentum conservation points still holds so by adding a new the angle you would still be in trouble and that that be notice Yes I had given you the which is bad but in this conversation I totally ignored the fact that I don't think that's kind of what I meant I apologize that was really bad me so Everything I set up to now was true of you don't know the angle when you watch the video it all makes sense to comply backwards from here any other questions but don't show I would trust that made it this far any other questions I'm edges go back and edit that part of a lecture so I look more intelligent Excellent now what we wanted you next having done this is what I consider algebraic with the the hardest part of the course and really I don't do a lot with exams but it's important for you see it and that is what he really end doing with elastic collisions and there's the challenge it's algebraically hard And and and it allows the collision now not every careful Atlasburg game End elastic collisions as opposed to any inelastic collisions Yad Saddam was worse than smaller animals will allow Molarity molality which I can either said I will have an object egg and have some velocity and be initially I will have an object bail out some velocity VEB initially They will call I also wrote that things can happen under draw 1 possible case velocity 8 object a wives and final velocity and velocity object B will have some final velocity of before and this is after that is I driven by going to the right afterward backing both collided legal in opposite directions after that both be be polite and be going to left after however there is 1 case in which we are dealing with reality what will not happen after the collision is an will be to the right of RGB going faster than others in the real world do not go through each other unless they shattered so if you have a collision where object a ghost Rule out the A bullet through Ricardo book through Apple through a block away that will never be a an elastic coalition that will be an inelastic collisions Because you destroyed the last kinetic energy destroyed stuff so when I'm talking about elastic collisions I could never have that on the other side of that Notice any questions on that nite I have for Now I have basically 2 equations that analyzed the collision so the changing kinetic energy is 0 and notice how many variables I have lots a room here to make a tight after the whole angle the Bacal hopefully we walk Now the text book Users Trying for a final velocity preferred actually write me I guess because I know I get lost but the prime just me That's the kinetic energy formula its conserved potential energy is considered a potential momentum to conserve because the collisions keep in mind the use of actors because a boring as a ready as you fall asleep or I write there so I have announced to equation so emasculated by true Vietnam's which is really what happened Dugan Salter the other 2 Now if I'm doing this in true dimensions of I have a collision where Say I'm shooting pool and the pool block on then It's another pro ball and they go off that way and that way Then I need X Y and from momentum I need used components so I do get another equation but I'm dealing with At the Y component is unknown as well so it's fundamentally the same issue at a roughly 2 unknowns to equations with 4 potential announced so I had to give you have information And what makes it wars is elder was very nasty because the user quadratic So they tend to be a lot they tend to be wanted to really really careful with your algebra There are some Olmert ones where I have you practice this fall nasty once when I want you out of focus on for the exam Israeli the special case by 1 Because of our movie only in 1 dimension all I have to worry about it say
That acts component and now life is just a little bit easier because of I'm clever that 1st of all out It always helps to quickly multiplied this equation by to the thing as a one-half they had to do with your 1 half of right down my 2 equations and I'm doing it a Wendy When I really have As I can rearrange things so I want all the mass of Eddie on 1 side the momentum equation looks like there's a notice the difference What's the difference was the difference between the left-hand side and the right hand side order that reports on the land which was 1st initial right which was 1st flight bans is electrode would be a summer let me be the right vessel but that's important but minus signs different saying thing with my kinetic energy now to anyone tell me why that might be useful what I just said There's 2 things you should notice about that By riding your quizzes that wedding 2 things when I think we did his way back with some of our kinematics bonds for solving them and I purposely rudder right under each other what What I do those 2 equations and get rid of I divide them what goes away the masses right so I divide the bottom by the time the last gentle Miami and on the right side cancer by now family you remember You're factory formulas for algebra 1 However what age for miners bees The idea a public at school A matter is now quarter was just amounts are up What is a miners The Gallardo whispering Lusby times egg miners and the same career so When I divide I get to cancel that echoes nor why wrote a bigger said to be a tight book that I had to cancel that so I actually get a new equation which it by organize as before so This is 1 of the few equations That's not unlike formula she but it is useful to them and now the the pharmacy because as incredibly specific situation If I had an elastic collision in 1 direction 1 dimension I get to use this this is the equivalent of conserving my kinetic energy of that I also get to use my momentum equation that I had before he remind but everything in here has a natural direction now right so it might be plus or minus That But now I have 2 equations into announced that a much easier equations to you because they're not quadratic so these are the ones you would actually use it was elastic and 1 dimension so it's a rare moment where there is an Extra equation that's worth knowing Any questions on them so all I did here was I took my kinetic energy and my momentum equations right and that a different obtuse squares I factor that and elected this equation and divided by that equation so the Midas is the masses camp about at all I was left with for the pluses and that was my error there but the poster in-kind it at the pretty Easy equation to use I'm not really a good examples with that is a a very small part of it But you do need now Before you pack up as we still have 5 minutes as a preview tour review of the class on Wednesday as a preview to studying for the final It is very important as you go back over everything to keep in mind I think the following questions now that you've seen every part of the course you want to be able to think in terms of motions somebody named for maybe some emotions we used in the course erupted amounted to the physics we've used it most often with what motion project are motion what another motion that we've had Circular motion what another motion that we've had that some having used the name before but I'm just collision and explosions and the way I never gave it named don't Saunders didn't tell you it's our motion along the surface right Down a ramp up a ramp a along a flat horizontal plane on remote and on services which either had friction or were friction but if you look at identified the motion that a big step for knowing what you need to do to solve a problem on the other side some physics winners was acceleration versus centripetal acceleration right to different types of accelerations which is basically kinematics kinematics was describing motion the other thing we did and keep in mind this had to do a situations there were instantaneous and the terrain Yeah will just stop there was we use Newlands life was a matter for the Jazz had to do with the instant the other physics we used a lot woes were worried about a before and an after we had some change in the state of the system that we took some version of work change in energy or momentum impulse and these became our conservation laws when appropriate and rally on this 1 page if you add in all the definitions that we needed to make this work and think about it right here we basically had 3 Definitions position velocity acceleration right here we had on the Amity forces with nowhere for 5 definitions for all the different forces energy We had for energy and momentum we 1 definition what momentum That kind of those 2 sheets reorganized and another useful way As review problems as you study keep in mind the challenge for the final Israel put 2 or 3 of these together in 1 problem and that's why recognizing what you did it each individual problem the key word when I said a lecture we note that this type of problem because of this that really help you a lot so Wednesday great review led to real article demos Friday tests had a good week
Kaltumformen
Masse <Physik>
Elektronen-Energieverlustspektroskopie
Kugelblitz
Leisten
Fahrgeschwindigkeit
Cocktailparty-Effekt
Impulsübertragung
Satz <Drucktechnik>
Minute
Gleiskette
Computeranimation
Schlauchkupplung
Druckbehälter
Raketentriebwerk
Druckbehälter
Fossiler Brennstoff
Zylinderblock
Zylinderblock
Fahrgeschwindigkeit
Impulsübertragung
Erder
Messung
Masse <Physik>
Kugelblitz
Leisten
Fahrgeschwindigkeit
Weltall
Impulsübertragung
Computeranimation
Juni
Regelstrecke
Transistor
Zylinderblock
Raumkapsel
Kapazität
Walzmaschine
Fahrgeschwindigkeit
Impulsübertragung
Kaltumformen
Relativistische Mechanik
Längenmessung
Energieeinsparung
Impakt
Tag
Standardzelle
Druckkraft
Übungsmunition
Steckdose
Stapellauf
Raketentriebwerk
Druckbehälter
Cord
Gleichstrom
Atmosphäre
Flüssiger Brennstoff
Jahr
Zylinderblock
Initiator <Steuerungstechnik>
Mittwoch
Raketentriebwerk
Sportrad
Atmosphäre
Flüssiger Brennstoff
Druckfeld
Biegen
Besprechung/Interview
Montag
Wasserbeckenreaktor
Raketentriebwerk
Phototechnik
Jahr
Besprechung/Interview
Ringgeflecht
Übungsmunition
Computeranimation
Pager
Masse <Physik>
Antiteilchen
Flasche
Kanone
Computeranimation
Raketentriebwerk
Stapellauf
Nassdampfturbine
Gleichstrom
Flüssiger Brennstoff
Druckfeld
Scheinbare Helligkeit
Pfadfinder <Flugzeug>
Kampfflugzeug
GIRL <Weltraumteleskop>
Tag
Kugelblitz
Minute
Computeranimation
Schwarzes Loch
Experiment innen
Schaft <Waffe>
Greiffinger
Messung
Rückstoß
Masse <Physik>
Gagat
Kugelblitz
Sonnenstrahlung
Fahrzeug
Fehlprägung
Leisten
Weltall
Cocktailparty-Effekt
Impulsübertragung
Nanometerbereich
Minute
Senken
Computeranimation
Uhrwerk
Woche
Umlaufzeit
Fahrgeschwindigkeit
Kaltumformen
Kraft-Wärme-Kopplung
Elektronen-Energieverlustspektroskopie
Elektronisches Bauelement
Intelligenter Zähler
Elektrizität
Brieföffner
Energieeinsparung
Proof <Graphische Technik>
Kugelblitz
Flasche
Kanone
Übungsmunition
Angeregtes Atom
Raketentriebwerk
Stapellauf
Nassdampfturbine
Gleichstrom
Innere Reibung
Jahr
Ringgeflecht
Initiator <Steuerungstechnik>
Papier
Erder
Greiffinger
Potenzialausgleich
Magnetisches Dipolmoment
Summer
Starkregen
Kugelblitz
Gagat
Fehlprägung
Weltall
Impulsübertragung
Nacht
Satz <Drucktechnik>
Minute
Wasserbeckenreaktor
Computeranimation
Woche
Druckbehälter
Rungenwagen
Kapazität
Biegen
Fahrgeschwindigkeit
Wasserfahrzeug
Pager
Kaltumformen
Pulsationsveränderlicher
Elektronisches Bauelement
Übungsmunition
Angeregtes Atom
Satzspiegel
Lineal
Elektrode
Anstellwinkel
Fliegen
Drosselklappe
Gasbohrloch
Feinstblech
Konverter <Kerntechnik>
Masse <Physik>
Bergmann
Wetter
Hobel
Echo <Ballonsatellit>
Zylinderblock
Spiel <Technik>
Passat
Herbst
Elektronen-Energieverlustspektroskopie
Beschleunigung
Gruppenlaufzeit
Tag
Abformung
Ruderanlage
Nivellierlatte
Druckkraft
Videotechnik
Schiffsklassifikation
Gleichstrom
Fernbedienung
Innere Reibung
Ersatzteil
Mittwoch

Metadaten

Formale Metadaten

Titel Basic Physics Lecture 25
Teil 25
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 10.5446/12936
Herausgeber University of California Irvine (UCI)
Erscheinungsjahr 2013
Sprache Englisch

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Fachgebiet Physik

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