 So questions from the homework and I recognize that some of you are going oh, I didn't do the home I I'll take questions still on Tuesday as well. Any of these you want me to go over? question three, okay Quiet, please Question three, and I think I think I think I sort of like question three I think I sort of like there in fact, you know what I do like question three I do like question three. I do like question three It says a 3.2 kilogram mass moving at 4 meters per second east hits a wall The wall exerts a force of 250 newtons to the west for point zero seven seconds Find the final speed and the direction Okay, we have a collision and we have a force. I think I'm going to be solving this using impulse I think I'm going to be solving question number three by going That's the equation you have on your formula sheet. Is that okay? Um Did they tell you the force? Okay, you have to say it louder and be a bit quieter the point. Sorry. What? Direction direct because now direction is going to matter. I see east and west now Uber paranoid. Sorry. What? Okay, I'm going to draw a little compass over here And I think I'm going to let east be positive and west be negative So I'm going to disagree with your 200 few newtons and I'm going to say technically what is it 350 or 250? I just can't okay. Hang on stop moving Stop talking say it loudly every time you said that first syllable someone's trouble 250 thank you now you keep moving and did they give me the amount of time involved point Point zero seven Seconds and what's changing anything and since momentum is mass times velocity. This is going to be mass the final minus mass The initial so far so good Did they tell me the mass 3.2 kilograms Excellent so I'm going to write this as negative 250 point zero seven equals 3.2 v final minus 3.2 and they did tell me v initial did they not Direction direction direction positive four negative four which one How do you know? Okay, we decided to be consistent here with this so positive four Otherwise, I put a negative four in there and out of a minus minus which would really change the answer quite a bit Okay Let's see what this side is negative 250 times point zero seven I get negative 17.5 equals 3.2 v final minus 3.2 times four 12.8 plus 12.8 to both sides. Yes I'll get negative 17.5 plus 12.8 and you'll notice I got nervous enough about this one that I didn't do this Algebraically I went to numbers because I was a little worried that with all the negatives and positives that I might do something sloppy I figure I'll be more careful with negatives and positives with numbers was by thinking I Get this Negative four point seven equals three point two The final now what to net And you're gonna get a negative. What's the negative velocity telling you direction is You know what it hit the wall and bounce off the wall its final velocity must have been To the wet whatever the four and the force that applied and that hit it I'm assuming it's a wall or head on collision was enough to not only stop it, but to set it backwards negative That okay, that's a great lead into today's lesson more questions Want you to put on your thinking caps a little bit here because what I'm gonna do is take you from To one dimension everything in a nice straight line Where the worst genetic that we have to do is let one direction be negative in one direction be positive and Two dimensions or we're gonna be doing lots of diagrams tip to tail tip to tail tip to tail And that's really the first question you start to ask yourself in this unit you say if I'm using momentum Can I is everything in a nice straight line? I'll let to the right be positive into the left be negative or to the left bean that positive into the right Be negative whichever is more convenient If I'm not in a nice straight line Raise your level of awareness and we'll talk about how we'll handle it first of all Example one a 30 gram bullet moving at 250 meters a second strikes a 50 kilogram Wood block which is at rest and sticks into it If the bullet and the block move together after the collision on a frictionless surface surface a Right a momentum equation B find the speed of the block after the impact and See just for giggles. Let's find the heat energy created during the collision. Okay, we can do all of that First of all, is there a collision? momentum Secondly Are all my motions in a nice straight line or do you see weird angles mentioned in this question? So straight line means I'm not going to be as paranoid I'm probably gonna let to the right be positive into the left be negative Every once in a while when I'm doing a question I'll notice it's way nicer to let to the left be positive into the right be negative But that's rarely usually my default is going this way Give me an elbow for me, would you? Yeah, it can wait. No, he was reading a history book Not the it wasn't the phone He was reading. He was reading very small type font with no spaces Which meant it couldn't be this because it didn't have any pictures and I would think that if Joel's reading it would have picture Oh, okay. Anyway, all right Joel you ready What does part a say to me my friend? I always start out by saying my momentum equation is gonna be this the sum of all the initial momentum Equals the sum of all the final momentum. That's where I start That's my hey, this is one size fits all and from here. I'm gonna break it down a bit further If a bullet and a piece of wood, so I'm gonna use B for bullet and W for wood or you could use mass 1 mass 2 whatever Before the collision, what's moving the bullet the wood or both? Bullet it's gonna be the momentum of the bullet initial Wham collision Equals is the collision After the collision, what's moving the bullet the wood or both? Both are they stuck together or are they separate? So if they're stuck together, I can write them as one momentum if they weren't I'd write them as separate It's gonna be the momentum of Both final Because I'm in a nice straight line I can go straight to doing algebra I can use dividing and subtracting things to both sides and adding that I can use my normal math eight I don't need to use vector math This is gonna be mass of the bullet the initial equals mass of the bullet plus mass of the wood The final okay now a said momentum equation the coal you could argue It's this you could argue. It's this you could argue. It's that I'm just gonna put the a there I'm gonna say there's my starting point B wants me to find the speed of the block, okay? B which of these is the speed of the block and the Bullet I assume Because they're stuck together which of these is the speed of the block and the bullet afterwards Vf are these in a nice straight line? Then I can just divide to get the VF by itself don't need to go all vectory yet Back the final is gonna be the mass of the bullet the initial All over the mass of the bullet plus the mass of the wood the final Is going to be Thirty grams is point zero three V is two hundred and fifty All over point zero three plus five Point zero three times two hundred and fifty all over Point zero three plus five You get one point four nine Yep One point four nine Meters per second what does C want us to find Jacob the heat what? You said energy now. I'm going to use conservation of energy not work because they didn't talk about work now I'm going to say for part C Kinetic energy initial plus potential energy initial equals kinetic energy final plus Potential energy final And plus heat Connor any of these zero Yeah fact, you know what I wouldn't have minded if you would jump straight to saying all of my kinetic At the beginning is going to be some kinetic afterwards and whatever is missing must have gone into heat In fact, this is almost the same physics of when I spammed those two metal spheres together Except there the final kinetic was zero and all of it went into heat. This is going to be a Half m v initial squared. What's starting at rest? Is everything at rest before the collision? What's moving before the collision? What isn't the bullet moving before the collision? Yes But Nicole you've raised a good point Here's what we're gonna have to do before the collision Nicole. What was moving before the collision only the So I better make a note. This mass is only the bullet Okay equals a half After the collision what was moving ah? Mass of the block sorry the bullet and mass of the wood the final squared Plus heat This is the first time that our masses aren't gonna cancel because we have different masses before the collision Only one mass was moving after the collision two masses were moving, but they both have kinetic energy Now can you all look up? This is the most common mistake. I saw in yesterday's test to get the heat by itself How would I move this over? What's happening in front of the heat right there? What sign is that a plus sign? How would I move this over then? Yeah, I had about 10 kids divide okay, I Had a whole bunch of students divide which told me a couple of things first of all told me they probably hadn't done much of the homework because he probably would have found out that that didn't work and Hey, that's sloppy throwing away math Not gonna divide the time thing the heat. How could I divide this over? I have to subtract it over in fact I'm gonna get this The heat is gonna be a half mass of the bullet the initial squared minus a half mass of the bullet Plus mass of the wood v final squared, and I'm running out of room here Moving up a little bit. I would love to show the numbers, but I just don't have room here I'm gonna go to my calculator I guess point five times mass of the bullet was point zero three times initial velocity point zero three Mr. Duke times initial velocity two hundred fifty square two hundred and fifty squared minus point five bracket mass of the bullet Plus mass of the block times the final squared you get nine hundred and thirty two joules of heat. Yeah He equals nine hundred and thirty two Joules Emily's looking a little bit clamped Didn't work on your calculator. Oh, you're really hungry. Oh man Did you have breakfast? example two the diagram below shows two pop cans of unequal mass initially at rest and Explosive charge is detonated between them boom and They fly apart. What can you tell me about their velocities after the explosion? Yeah How about let's call it small can and big cans that you're really having a tough time working your tongue around the words so Go for it. What we got. I agree small can't first of all I can I think we can even be more specific than that. Let's see What I think the small can and go twice as fast the big can and go half as fast in Opposite what? You know why opposite directions? First of all, is there an explosion? What I said to you was I use momentum when there's a collision or an explosion in the shorthand I said when there's a jump explosion collision, I think momentum. What's my momentum right now? Nicole, what's my momentum right now? So what's my final momentum have to be? Has to be okay, so I'm going to go like this Zero equals the sum of all the final momentum And this is a nice also segue from Jeanette's question earlier today because since we have them traveling in opposite directions But in straight lines all that one direction be positive in one direction be negative. I'm going to get this zero equals momentum of small plus momentum of Big fact let's minus the small over Negative momentum of Small equals momentum of big Momentum is what times what? so I'm going to write this as negative momentum small velocity small equals Moment mass big velocity big So far so good, but what do we know about the masses? How big is the small mass? What did we call it? And what do we call the big mass? Oh? Let's stick that in negative m v small equals 2m v big Brett what happens to the m's? They do and in fact you get this final answer the negative small velocity is twice as big as The big velocity. What's the negative telling me in the opposite direction the small one is moving? Twice as fast as the big one, so we've actually done an algebraic proof of what you intuitively saw I don't know if I look for something quite this detailed and again You could always just make up reasonable numbers and crunch the numbers and say oh, it's twice as big That's that's fine, too, but there's a lovely algebraic Which one is bigger? This is going twice as fast as that right in other words if this is going 10 You just per second how fast is this going five to make this equal I better put a two there so I can get 10 equals 10 Don't feel bad everybody does that twice as fast. Why isn't the two on the twice as fast side? because The two needs to be on the twice as slow side to make the equation balance So that's all been a nice straight line some terminology here and now we're gonna go two dimensions important terminology There are two main types of collisions There are two main types of collisions. The first type of collision is An inelastic or completely inelastic collision The second type of collision is an elastic collision Unfortunately, first of all the words sound an awful lot alike when I say inelastic and an elastic you have to listen very closely I'll we try and pause there's any elastic collisions and then there are elastic collisions What's the difference between the two any elastic is when the masses stick together for example? if two cars t-bone each other and the wreckage sticks together and they move off together or Nicole like the block and the bullet that we just did those stuck together. That would be an inelastic collision Elastic collisions are when the masses bounce off of each other curling body checking and hockey Playing pool and hitting a billiard ball with another billiard ball. Oh any elastic Tackling ideally you're hanging on and sticking together. Yes so We have any elastic Then we have partly elastic and perfectly elastic. You know how I remember the difference What's an elastic band? What's that you all know when it tell me what when I say the word elastic band. What's an elastic band? Matt you said the magic word what? Here's what I remember elastic rubber bounce. They bounce off each other Any elastic is the opposite of bouncing off each other That stuck together So if you're looking for a dumb way to remember I and I do this still after 15 years Well, you know years from taking my physics whenever someone says it's an elastic collision You'll see me go unfocused for a second. I'm thinking elastic elastic band rubber band a bounce They didn't stick together. They bounced off each other Okay, now in all collisions in all collisions Momentum is conserved in other words the sum of all of them into minstrel equals some of all the final in a perfectly elastic collision in a Perfectly elastic collision you have something else that's conserved in a perfectly elastic collision Kinetic energy is conserved now What's a perfectly elastic collision well for a perfectly elastic collision to occur You need the following both objects must have the same mass They must rebound it apart at a 90 degree angle So if the question says it's perfectly elastic you can assume the angle they fell apart at was 90 degrees I'm not gonna do a huge song and dance about this You are gonna see in the review a couple of times once or twice There'll be a question and you'll go mr. Do it They didn't tell me the second mass and they didn't tell me what angle they flew apart at and I'll say does it say perfectly elastic? And you'll say yes, I'll say well then they don't need to tell you the second mass and They don't need to tell you the angle example 3 a 60 kilogram hockey player traveling 20 meters towards the north Collides with a 50 kilogram hockey player traveling one meter per second towards the west the two become entangled together That means this is any elastic because they stuck together Can you see that this is no longer in a nice straight line Kara? See the directions Okay We're gonna start out the same But we're gonna be way more paranoid and they want to find to be final with what velocity to move up after the collision Eric do you see the word north mentioned in this question? I'm gonna draw compass rose over here. Is that okay Trevor? Okay Trevor is there a collision? I'm gonna start out by going the sum of all of the momentum before the collision has to equal the sum of All of the momentum after the collision so that hasn't changed Before the collision what was moving mass one mass two or both? Sorry Both where they stuck together before the collision Okay, so I'm gonna say this before the collision. I have mass one initial. That'll be the first hockey player Andrew Plus mass two initial that'll be the second hockey player equals Wham collision after the collision Who's moving mass one mass two or both? Both stuck together or separate Now right now some of you are saying mr. Dewick This is exactly almost exactly the same equation as you've used on the straight linear ones so far Now though we are not we are not we are not going to say momentum is mass times velocity We will eventually Now we're going to dull We're going to dull We're gonna draw a picture What direction is the first hockey player traveling? plus What direction is the second hockey player traveling? Equals i'll leave the right side blank for a second now I how will I add these two arrows together draw them? Problem I don't know how big the arrows are. Oh, yes, I do momentum is what times what? So the mass of the first hockey player is 60 Times the velocity is two. You know what? This arrow is 120 long Is that okay connor? And what about the second guy well his mass was 50 His velocity was one This arrow is 50 long How long is the first arrow? How long is second arrow? So if I want this to look roughly to scale this arrow should be a little more than twice as long as this guy Okay So ready? 120 50 See the difference by the way. This was the same but now we're actually adding pictures What's my resultant? What am I how am I going to draw it first of all it's always from The tail of the first one to the tip of the second one. You know what? They're going to move off together in that direction and i'm going to call that on my diagrams a Momentum of both final Now this is a lovely right angle triangle, which means I can use so katoa and pythagoras So let's do that. How can I find out how big this is? Well momentum of both Squared is going to be 50 squared plus 120 where it's pythagoras And ze when you did that and then you took the square root What did you tell me the momentum of both is equal to? Okay Sorry Don't care yet because they didn't ask me to find the momentum final What did they ask me to find ze? Final velocity that's momentum Momentum is what times what? Ah I'm going to say this the mass of both The final equals 130 Emily, how can I find out the final velocity? okay The final is going to be 130 divided by 60 plus 50 What's the final velocity that they move off together? at Connor would you get oh never mind? I thought you were typing sorry You could be if you wanted to john would you get I can't hear you 1.18 meters per second And we're still wrong technically we haven't found the velocity You know what we found the speed Velocity has two things magnitude and what? so the final Vector equals 1.18 meters per second at There's my direction Ze which trig function can I use to find this angle? tan theta Equals remember all the spokes opposite over adjacent How do I find an angle? Yeah shift tan Making sure I'm in degrees. I am And I get 23 22 points. I'll go 23 degrees 23 degrees what of what? Jacob west of north By the way, do you see how as soon as you go non-linear not in a straight line? That's a lot more work But it opens up some very cool questions that we can solve because I'm going to tell you right now Most car crashes aren't in a nice straight line. You get t-bone. You get broadsided. You don't hit head on Turn the page Let's suppose in example four Oh, by the way, I love example four. I love example four except I'm going to put a little star next to this. This is advanced I'm not going to cross it out But we may not do it today finding the final amount of kinetic energy in the initial amount of kinetic energy And then subtracting there is one like this in your review. In fact, you know what? I am going to temporarily cross this out Let's do that But on your test in this unit the written section is going to be a collision at an angle Can you see Brett just by glancing at the diagram that we're not in a straight line? Is there a right angle here? This is going to be sin law cosine law stuff Is there a collision? What do they want me to find? Okay, you said there was a collision. I'm going to start out exactly the same by going The sum of all the initial momentum equals the sum Of all the final momentum Mitsu, that's my fallback stand by get my thoughts organized my questions no longer blank But now I'm raising my level of paranoia of being careful You know what I'm saying? The angle is going to be careful here. Before the collision Nicole, what's moving mass one mass two or both? Which one? No, how how which which of your answers that you said was correct mass one. I agree. Why how do you know stationary? Okay? yes so mass one initial equals After the collision, what's moving mass one mass two or both? Nicole are they stuck together or are they separate? This is an elastic collision not perfectly elastic because the masses aren't the same and it's not a 90 degree angle Which would make everything way easier anyways. It's an elastic collision. So I'm going to write this Nicole momentum of the first one final plus Momentum of the second one final Underneath this I'm going to dull The first momentum looks an awful lot. It seems like that equals Looks like the final momentum of this small mass looking at the picture Looks like that looks like the final momentum of mass two looking at the picture Looks kind of like that. I can fill in some of these because momentum is what times what breed? 16 Yeah right Uh, oh this is mass. Oh, I can do this one two times six point seven Which is I think 13.4 13.4 Can I fill in this one? Nope. So I'm just going to label that as mass two final Okay How will I draw this vector triangle? Well, how will I add these two together? And here's the nice thing When I add these two together, they're supposed to give me a horizontal line because that's what that is So here's how I would draw this watch I would go, okay I got a 13.4 I know to stop drawing this right here Not this far And not shallower the reason I know is Apparently when I add momentum one and momentum two final, it's supposed to add to exactly horizontal 16 This plus this has to give me that Oh, and they gave me an angle did they not Somewhere in my diagram originally see it see it see it Apparently this angle right here is 10 degrees. Oh 10 degrees So katoha No No right angle Sign law well, I would use the sign law if I knew both of those or both of those or both of those Do I have a pair anywhere? This is cosine line in fact It's going to be cosine law almost every time and you're going to get good at the cosine law What is the cosine law you ask? What is the cosine law you ask? Yes Cosine law says this how much room do I have lots of room still good C squared equals a squared plus b squared minus two a b Cosine big c Where mitzvah There's c right there what I'm trying to find Momentum of object two final squared equals What's a Nice thing is as long as you identify c correctly as being across from the angle It doesn't matter what you pick is a and b. It's going to be those two So i'm going to go a is I hack 16 squared b is 13.4 squared minus two times 16 times 13.4 Cosine what's big c 10 degrees The nice thing is if you've listened to my advice about getting a good calculator You should be able to go do this in one fell swoop 16 squared plus 13.4 squared Minus two times 16 times 13.4 cosine of 10 And I get 13.27 which is wrong What what what what bret? Yeah, I found momentum squared The final momentum of object two is going to be The square root of that 3.6 4 3 4 And i'll carry a few extra sig figs Because they didn't ask me for the final momentum Brett you're looking puzzled am I wrong Then we'll check uh, are you have a graphing calculator? Okay, make sure you're in degrees because the graphing calculator is by default going to radians if you've ever reset them Or replace the batteries or anything like that. I think i'm right in fact. I'm sure i'm right And then square root yes Brandon momentum is what times what our vendor momentum is what times what? So this is the momentum and I want to find the velocity. I think i'm going to go like this then Velocity final is going to be 3.6 4 3 4 divided by mass 2 that's going to give me the final velocity of the second object Actually, it's going to give me the final speed Get through some more tree What do you get for speed of object 2? What was the mass of object 2? I've scrolled down it was oh 10. Oh, I can do that in my head then 0.364 Meters per second is not moving very fast Which it shouldn't because it's a big heavy mass and it only got grazed by a much smaller mass at I'd like to find That angle I'd like to find don't write this down because i'm really going to gum up this diagram That angle Where does that angle appear in my triangle? Can you see the zed? I think if I want to find this angle What I really need to find is that angle And then go What of what for that? Does that make sense? Connor are you good? Sure because you're not looking good You are Okay, so i'm going to go like this That's theta That's theta How can I find theta soca toe? No sign law Wait a minute. We couldn't use the sign law because we didn't have a pair We do now have a pair because we just figured this out Which is why I carried a few extra decimals on my calculator The sign law says this The sign of our mystery angle divided by Okay, mr. Do it turn that off now I'm going to call this theta Come on I'm going to call this theta. I'm going to call this theta. Sorry. I forgot to turn up. What's going on here Change colors, mr. Do it. Let's try this again Hmm problem Let's do this mr. Do it. Ah, there we go. I don't know what was going on there So i'm going to call that theta And that theta This is the angle that I really want but I can only find it by finding that one It's going to be the sign law because I'm going to have this the sign of my mystery angle divided by what's across from it 13.4 equals The sign of 10 degrees divided by what's across from it, which I didn't know at first but now emily I know it's 3.6 4 3 4 make sure you use the momentum and not the velocity When I cross multiply I'll get sine theta equals 13.4 Sign of 10 degrees divided by 3.6 4 3 4 By the way, this is almost as much work as you'll do for any one question all year 13.4 sine of 10 divided by 3.6 4 3 4 and oh Theta is point 60. Oh, no, no, no. I didn't find theta. What have I found? Sign theta, how do I find theta? Second function sign of my current answer Ah 39.7 or 38 degrees. Sorry for or 40 degrees I'll go 39.7 39.7 degrees What of what? What is that? What of what? Mitchell north of east Seven marks ready one mark Two marks three marks Four marks Five marks Probably actually a half mark and a half mark Probably you also one mark for that six marks And I find another way to give you part marks in there. Can you skip steps? Yeah Would I not unless I got really good? Yep Okay You know what your written question is going to have probably three collisions Probably one on a nice right angle, which takes um, dare I say it way less time It's going to be two Where they are not in a nice right angle Now I'm going to also though say although the math is tricky if you're careful It's reasonably plug-and-chug. There's just lots of room to make sloppy mistakes, too We're going to come back to example five We're going to come back to example six example seven A 10 kilogram curling stone is sliding along the ice. No friction When it hits a stationary 18 kilogram bucket of sand after the collision The curling stone's velocity is three meters per second east and the bucket has a velocity of 2.3 meter second at 43 degrees south of east What's the initial velocity? So here instead of saying be final it's saying. Hey, how fast was the stone coming in at? And this one is trickier also because no picture We're going to have to really think ready Is there a collision? Are we in a nice straight line emily? In other words, can I just let to the right be positive to the left be negative and just do my usual cross multiply divide and subtract junk How can you sorry easily at almost a glance tell that we're not in a straight line? south of east east north Angles So you ready? Are we in a nice straight line? No Going to get a little more paranoid then i'm going to draw a little compass rose over here So I don't do something dumb And but now I repeat I work my way back through the same set of questions before the collision What was moving mass one mass two or both? The momentum of the stone initial Wham there's a collision After the collision what was moving mass one mass two or both? stuck together or separate in elastic momentum of the stone final Plus momentum of the bucket final Why because emily this is not in a nice straight line Did they give me the initial direction of the of the stone as it was coming in? I'm going to hold off on that drawing that I'll come back to it. I am going to put A little equal sign here Did they give me the final Direction of the stone? Oh, yeah due east And velocity is not conserved momentum is conserved mass Velocity due east with a momentum of 30 plus Did they give me a direction for the bucket? Yep What 43 degrees south of east? There's east 43 degrees south of east How big is the momentum of the kit? What's the buckets mass? 18 what's the buckets velocity? Oh, okay 18 times 2.3 41.4 I'm still not quite sure what this one looks like but I can tell you what this looks like how would I add these together brie draw them Okay As a picture this is going to look like this 30 41.3. Oh What's the resultant here look like? That's momentum of the first What did I call it? I use the letter s didn't I? Momentum of the stone initial Which if I go back here means it must have looked like this Caitlyn is this nice right angle so katoa Oh And in fact, I got a real problem right now. I don't even have an angle. Oh hang on. Hang on. Hang on. Hang on I got this angle Yeah Which is This angle How big is this angle? Caitlyn what you're right Doesn't help me at all How big is that angle? What are those two add to? Okay, so how big is this angle inside the triangle here 137 And I can tell I'm gonna run out of the room so bear with me while I do this No, how will I find momentum of stone initial? Well cosine law Momentum of stone initial squared equals b squared plus c squared minus 2 b c Cos I'll hang on mr. Do like you're writing it the way that they don't like my back you guys like A squared plus b squared minus 2 a b cosine c I'll be honest. Nicole. I don't have the actual formula memorized What I know is this squared equals that thing squared plus that swing thing squared minus two times that times that cos that It's the side angle side across So this is going to be 30 squared plus 41.3 squared minus 2 don't forget the 2 times 30 times 41.3 cosine of 137 And again Mitchell this equation is on your formula sheet You'll probably end up memorizing it for this unit though because you use it so often 30 squared plus 41.3 squared minus 2 times 30 times 41.3 times the cos 137 What the it's traveling 4,000. Oh, no, no, no, no, no, that's a square root square root square root, right? Oh, and that's not its final velocity. Anyway, that's its final moment initial momentum 66.468 41.4 or 41.3. I thought it was 41.3, wasn't it? Oh, I put a four there and a three there Oh, that's silly of me This was uh This was 18 times 2.3. Yes I think it's 41.4 Kara candy for you If you see me do something dumb like that try and point it out sooner so that all the people at home Aren't freaking out when they're looking at this lesson online Which is going to change that as well and that as well Put a four there mr. Dewick Let's go try that again Four four So you get that and then square root How about 66.563? Thank you Kara. Okay, that's the that's the momentum initial. How do I find the velocity initial? If I know momentum, how can I find well first I can find the speed divide by the mass so So I'm running out of room velocity of the stone initial Is going to be this number divided by the mass of the stone, which was 10 Initial velocity is going to be 6.5 Sorry 6.66 Get the homework off someone at Sean what angle this angle right here? Which is going to be what of what by the way South to east yeah, it was coming in south of east and then I guess it got deflected straight sideways And continued this way so let's see Sign of theta I should have left more room clearly over 41.4 equals The sign of the angle that I do know Over the side that I just figured out which was 66.563 When I cross multiply I'll get 41.4 times the sign of 137 divided by 66.563 And I take the inverse sign of that sorry. I'd love to be able to fit this on I think you get 25 degrees south of east We're going to temporarily pause here. I'm going to get a couple of questions to try and then we'll pick up with this on tuesday What questions can you try right now? Uh strangely enough, there's no homework attached to this is there. Ha that's a little silly Okay revising that I have a take home quiz for you not on today's stuff But on the last few days worth of stuff