We made quiz questions to help you review the content in this episode! Find them on the free Crash Course App! Download it here for Apple Devices: apple.co/3d4eyZo Download it here for Android Devices: bit.ly/3TW06aP
Bless you for colour coding your lessons. I have severe adult ADHD and your thoughtful, color-coded and disability-friendly teaching style and execution is done flawlessly well. A marriage of tantalizing substance and effusive warmth, truly truly make me feel as though I am learning, sitting at grandmother's knee, with a gentle fire in the deep hearth at my back. Thank you thank you thank you! All other teachers should take a lesson of their own by adapting the curriculum in this way.
Velocity Velocity →v is a vector physical quantity that expresses a change of the position vector →r in a unit of time Δt. In the SI system, the basic unit of velocity is ms. Velocity expressed in ms provides information about the number of meters travelled by an object in 1 second of motion. If a specific direction can be assigned to the motion, then velocity is also a directed (vector) quantity. This means that velocity has: - a direction - the same as the direction of motion - a sense - identifies the side in which the velocity in the specific direction is orientated - a value - the length of the velocity vector →v Depending on the velocity, the following categories of motion are identified: - uniform motion (constant velocity in time) - non-uniform motion (velocity changing during the motion) Average velocity Average velocity →vavg defines the rate of change of the position vector Δ→r in time Δt not approaching zero. It is defined as the ratio of displacement Δ→r to time Δt in which the displacement took place: →vavg=Δ→rΔt The direction of the average velocity vector is the same as the direction of the displacement vector.  A material point at the initial moment t1=0 was in position A. After some time, at moment t2=t, it was in position B. The displacement of the point is: Δ→r=→r2−→r1 The time in which the displacement took place is equal to: Δt=t2−t1=t Instantaneous velocity Instantaneous velocity is the velocity of a body in a time interval approaching zero. This is why it is defined as the limit of the quotient of displacement Δ→r to time at Δt approaching 0: →v=limt→0Δ→rΔt Differential notation:→v=d→rdt Unlike average velocity, instantaneous velocity detects sudden changes in the movement of a body. For example, the body did not move for 1 second. For another 1 second it moved over a distance of 2 meters. The average velocity during 2 seconds is equal to: vavg=ΔrΔt=2m2s=1ms Even though the body did not move in the initial phase of the measurement, its average velocity is not equal to zero. If the motion is considered in intervals approaching 0, the initial values of instantaneous velocity are equal to zero. The direction of the instantaneous velocity vector of the body →v is the same as the direction of a tangent to the path of the body in the point where the body is located.  Acceleration Acceleration →a is a vector physical quantity that expresses the change of the velocity vector →v in a set interval Δt. Thus, it can be said that acceleration defines how fast the velocity of an object changes in time. If a body moves with constant velocity v, its acceleration a is equal to 0, and the motion of the body is referred to as uniform. In a straight-line motion, the direction of acceleration is the same as that of velocity. In this type of motion, acceleration only affects changes of velocity: it causes it to increase or decrease (depending on the sense of the acceleration vector). If the sense of the acceleration vector →a is the same as the sense of the velocity vector →v, the velocity of the body increases and the motion is referred to as accelerated motion.  If the sense of the acceleration vector →a is opposite to the sense of the velocity vector →v, the velocity of the body decreases and the motion is referred to as decelerated motion. In this case, instead of acceleration, there is deceleration.  The unit of acceleration is ms2. This results from the following formula: mss=ms1s=ms2 Acceleration in a curvilinear motion In a curvilinear motion, the direction of the acceleration vector is at a certain angle to the direction of the velocity vector.  In this case, the acceleration vector has two components: - A component parallel to the velocity vector (tangent to the path and parallel to the direction of motion) - this is a tangent component a|| that corresponds to the change of the value of velocity. -A component perpendicular to the velocity vector (perpendicular to the direction of motion) - this is a normal component an that corresponds to the change in the direction of the velocity vector. In perpendicular motion, the value of this component is equal to zero. Average acceleration Average acceleration of a material point in a set interval of time is the ratio of the increase of the velocity vector Δ→v to the time Δt in which that increase occurred: →aavg=Δ→vΔt The direction of the average acceleration vector is the same as the direction of the change of the velocity vector.  At the starting moment, a material point t1=0 moved with the velocity of v1. After some time, at the moment t2=t, its velocity was equal to v2. The change of velocity during the motion is equal to: Δ→v=→v2−→v1 The time in which the displacement took place is equal to: Δt=t2−t1=t Instantaneous acceleration Instantaneous acceleration is acceleration of a body in an interval of time approaching zero. Instantaneous acceleration is defined as the limit of the quotient of the vector of change of the velocity Δ→v and the time Δt in which the change occurred: →a=limt→0Δ→vΔt The direction of the instantaneous acceleration vector is the same as the direction of the change of the velocity vector.  Differential notation: →a=d→vdt=d2→rdt2
This is completely unrelated, but can we PLEASE get a CRASH COURSE SERIES on PERSONAL FINANCE? Considering that these series are primarily directed towards high school and/or college students who are preparing for their lives and may not be receiving the best education from parents and/or school, a course on personal finance would be incredibly beneficial to your audience. Not enough young people know how to use their money correctly (myself included). For example, you could cover topics like: how to write a check, how to plan and organize a budget, how to invest, how to choose a good bank, how to open a bank account, how to go about purchasing a car or a house, or how to choose a good apartment, how to figure out what kind of salary you would need to maintain your current or preferred lifestyle, what careers would make you that salary, what major you need to get that job, how much that major would cost and how many years it would take, how to take out a loan (student or otherwise), how to/ if you should use a credit card, how to choose a good university, how to ask for a raise, how to prepare for an interview, how to fill out job and college applications, how to choose a good community to settle down in, how to choose an insurance company, how to watch out for scams and cons, how to plan out the next few years of your life, how to save for retirement, how to fill out tax forms, how to find a good attorney, how to conduct yourself in a civil suit, how to market your skills, which skills do employers look for in new hires, how to plan your schedule / calendar, good time management, how to write a letter, etc. The list goes on and on. I admit this was quite exhaustive and demanding, but I think that not enough young people are properly prepared for the important, often complex and not straight forward, daily struggles and demands of adult life. It can certainly be seen as a failure of our public education system, because, beyond providing a basic worldly understanding and general background knowledge, primary school should prepare students for life after school. Instead, we are just thrown out into the real world, which has very little in common with school, and expected to know what we are doing. This is unfair to young people who would otherwise have very bright futures, but have no idea how to even fill out an envelope.
I highly recommend the channel How to Adult. They have over 4 years worth of videos on a range of adulthood related topics and 31 videos on personal finance. It's not of crash course, but Hank and John are executive producers of it and even host episodes from time to time, so it still has a crash course feel to it!
How I solved the equation (took me a while to understand) 122 m - 0m =0m*7s + 1/2a7s^2 122 m = 0m + 1/2*49 (because we're looking for a, and because 7 squared is 49) Then you divide the fraction (numerator ÷ denominator) 1/ 2 = 0.5 And multiply 0.5 with 49 0.5*49= 24.5 And lastly, divide 122 through 24.5 122/24.5 = 4.9... And round up to 5 Which is how you get to 5 m/s^2
Dear physics students, This is a good supplemental source but you really need class and really really really need to do the homework. Sincerely, A person who has to grade your homework.
+sac12389 Absolutely. This course is structured as something of a supplement to AP Physics, not a replacement for it. DO YOUR HOMEWORK, LEARNED AND ASTONISHINGLY ATTRACTIVE PUPILS!
Tiwinee Don't! stick with it! there are other, longer, slower explanations out there. Follow a video explaining how to do a problem while you are doing a problem! pause it after each step. Then do a problem without help. Always write down what values you have, what values you want and then find the relevant equations.
Funny, did you know what you just do? Do you? You, somehow, managed to sum up my entire Physics class for FIVE WEEKS about kinematic into FIFTEEN MINUTES. I'll definitely share this.
I bet your teacher would be happy to cover the whole lot in 15 minutes and take a few weeks off - but you wouldn't learn a thing. As a new learning concept - and this is about year 9 stuff - a few weeks is pretty fair. As a physics teacher talking to another physics teacher I'd say 15 minutes is a fair time to summarise this amount of learning. Of course you might be the genius who can follow it at that pace, you're just stuck in the wrong class, so sorry about that. Or you might be at uni covering year 9 material, who knows?
Actually, what you said isn't valid. The problem is that you already KNOW the material, and so you think the video sums up everything. Let's assume you don't have physics class and have 0% of physics info in your head (ahem, me). You watch this video. What do you learn? Just a bunch of equations. You don't just memorize the tools. You have to apply and actually UNDERSTAND the reasoning behind all this. I'll come back to this series after taking physics classes (online, that is.)
Ha...I did that for years with my first car. Speedometer AND gas gauge were both broken. I figured if I just drive a little slower than the guy next to me, I'm good.
I just wish teachers would be more blunt with physics utility and say it only useful in engineering or understanding the universe, and won't help in day to day life. These pretty imaginary scenarios that are made up to shoehorn in a day to day use isn't good and misrepresents what it is about.
+Sebastian Carrier how to measure one's perceived time in this equation? As we all know time moves different depending on the space we move through and how fast we're moving
My expression went ok..this is easy...yeah..yeah??..hold up...slow down...wait what the fff....back up back up *rewinds the video for the 5th time* OOOOHHHHHHHHH
I'm sorry you don't understand this it takes a "real" teacher to explain these properties well even though after hearing it before I understand what she's saying.
Crash Course is an amazing source, but remember thanks to a load of comments warning Crash Course lovers out there, don't use this in place of homework. It's just a heads up. On another note, this is an amazing video which helps me get the basics down. Time, position, velocity and acceleration. Though a slow-down might be necessary for equations, it made my head spin. I'm watching this in hopes of me understanding the physics course later for the school year. Plus, hey, who doesn't like physics? I mean psssh, look at it, if you get past the equations (*frowny face*) it's really interesting! Thanks, Crash Course!
*dies in a hole* I don't do good in science... so I have to keep on rewatching Crash Course videos to get the ideas in my head. Then there's math and language where I get As and don't need to study.
Thank you Dr Shini Somara for showing other women that physics isn't just for men and for breaking harmful stereotypes that keep women and girls from studying STEM or succeeding in STEM. So many of us drop out or avoid STEM fields because of how threatening the environment can be, you are showing us that you can break through and succeed, you just have to keep strong and do what you love no matter what others think. Thank you for being such an inspiring woman. Sincerely a biomedical science/engineering student.
Yes, that is a mistake, it is actually the instantaneous velocity. Funny thing is, they already gave the correct definition of average velocity. I think the trouble is that they seem to be teaching this course without acknowledging the calculus that is used to derive these equations. Velocity makes sense as m/s as an average, but instantaneous velocity is a more nuanced idea that they kind of skirted around here.
@@audrivalentin4451 Science is so broad. I am a Science teacher, teaching Chemistry and Physics, but I am fine with math. I know some Science teachers such as those teaching Biology, etc, who have problems with Math, but you can't be a Chemistry and Physics teacher if you are terrible with Math.
A= (v2-v1)/(t2-t1) M=(y2-y1)/(x2-x1) V= at + v0 Y= mx + b V=d/t M=rise/run I noticed some similarities between velocity/acceleration and slopes. I used to wonder what the slope was useful for but math is everywhere! If this is obvious, I apologize (public school failed me and taught to test) I'm currently trying to rewire my brain and reeducate myself
Dr. Somara, I'll be honest: I was disappointed that Hank wasn't hosting. Two minutes into the first episode and I was wrong: you love this stuff! Rock on, Doctor!
Hi here are some teaching methodology things that could make this easier to understand (because I had already studied this before watching the video and thought I understood it but could not follow the video at all, despite it not having any new information in it) -Put the list of things that will be studied at the beginning instead of the end (if you can summarise very briefly what each thing is about that's even better) (compromise: put them in the description) (this is called previewing) - ASK QUESTIONS all the time, and pause to give people a chance to think (or instruct them to pause the video if it will require more time) Sometimes one thing logically follows from another, and if you ask people to figure it out not only does it keep them paying attention, it also helps them to remember. That's one type of questioning. Another type is more obvious, more like a test question, where you give people something similar to do just with different numbers, and say you will give the answer next week (and people can help each other in the comments). - Explain everything without using math symbols first, then explain it again using maths. You can't use maths to explain things to ordinary people, you just can''t. - You can speak at any speed as long as you pause occasionally. This even works for people for whom English is not their first language (they just need more pauses). I.e. No jump cuts -Have concept checking questions at the end of the video for people to answer in the comments. This encourages self-recitation and improves memory as well as allowing students to notice which parts they did not understand. You are already using visuals, movement, connecting it to things we already know, showing enthusiasm, so this is all good. But otherwise the teaching methodology is very old fashioned and such a difficult subject would especially benefit from modern methods.
for those of you who dont understand , watch the video a few times, stop , rewind etc. Almost like reading a textbook.You go back and forth through text until you understand.
Thanks! I have some problems learning physics since my 6th grade teachers aren't very helpful! I want to learn quantum physics but I figured it would just be better to start out from the beginning 😂
@@_sweethoney.gacha_3617 You go! Quantum physics are interesting even though it makes my head dizzy sometimes... don't worry me too, my teacher was nice, but she got off track sometimes...
@@_sweethoney.gacha_3617 way to go, good luck! Hope you won't end up like me (slacker), I graduated school this year and I'm going to university to learn oriental studies and I dunno physics except for basics, but I'm gonna watch this course as a challenge, plus knowledge from many different areas won't hurt!
+CrashCourse In the future I cant wait for Crash Course ''robotics'' Then i''l learn about roboids robo hands how they work and function, and how I may be able to augment my self with robo hands that can crush a rhinos bone the veil between science and science fiction is growing thin i am both excited and terrified
+CrashCourse So technically not a physicist? :P Like ... Does she understand how to do calculations in QEd with amplitudes etc? Not that I do, then again I'm not a physicist either. I mean not to be rude or dismissive of her just wondering if she knows physics... Like really knows physics, or if she's just Presenting physics..
+RomulessI Dude, read it: _mechanical engineering_ and *_FLUID DYNAMICS_*. It hardly gets any physics-er than that. and btw, the calculations in QED are not at all more difficult than those in fluid dynamics - the concepts are different and sometimes more abstract, but hooooo boy the differential equations in fluid dynamics O_O
As a 2nd year A-Level physics student I'm looking forward to the rest of this series, especially since you managed to explain the first week of my course last year into 10 minutes. The one very minor thing that bothered me was that Δ is upper case Delta, lower case Delta is 𝛿 and is used for very slight changes (e.g. temporary dipoles in diatomic gasses due to Van der Waals forces, 𝛿+/𝛿-). But then again I'm quite an OCD person when it comes to that type of thing so ignore me. Regardless, I'm hyped to learn more!
Taking physics for the first time ever next semester. Thought I'd come here to get a head start... after watching this, it's safe to say I need all the help I can get. Wish me luck.
I gotta say this is a little too complicated for first time learners. I'd recommend going to Khan Academy first and learn physics there, and THEN watching this series.
Wow, I loved this. I mean, before, I sort of hated physics, but then I started watching your videos and I've definitely changed my mind. Thank you so much Shini Somara.
okay, i'll be honest, for a refresher, this is good. for someone who's totally new to kinematics, well play at half speed and maybe you won't have to go back. she's going way too fast and the examples are very basic but they're not that fun or engaging examples. it's like a teacher trying to be relatable but doesn't know how. or hank's episode about carbon.
While I'm disappointed by the comments, I'm really really happy that Crash Course Physics is taught by a woman. As a woman in engineering, it's nice to have someone familiar to learn from.
+ni ni depending on context it could be an incremental change or any given change. in situations where you aren't doing increments, they can be used interchangeably.
This was extremely helpful, and extremely insightful. I'm very grateful that you guys at Crash Course have made this Physics series a reality. I took notes and even drew graphs throughout the whole episode!! This is seriously helpful, thank you so much. Please keep these episodes coming
As with other crash course series, the first episode should be a roadmap to the topic. Let people know what is going to be covered and introduce those completely new to the field to the basic questions the field tries to answer. This is a decent episode 2 (I think perhaps more content could have been injected, but I'm biased).
*when the school closes till the 30th because of the corona virus so as a bored nerd you decide to watch this video and study even though there's no test*
+Nikolaj Lepka still it's the upper case delta that is the correct symbol to use here. Lower case delta has it's own little area I seriously doubt they will involve here.
Getting out of speeding tickets is not the best way to explain to people why they should be interested in physics. But, good luck with this video series.
Future EPs should be slower, and have more graphics so we can see what she's talking about in action. Maybe I'm dumb all these words just blend together, making it hard to absorb the concepts.
Others have mentioned the delta issue, let me just reiterate - the symbol used is UPPERCASE delta, we just write it sort-of smallish in size. Lowercase delta is also used, for other things. The bigger problem is that your first kinematic equation is just wrong as you state it. It is not the AVERAGE velocity that equals v0+at. It is the FINAL velocity. The average is something completely separate. Other than that - good job so far.
Kzxo500 but isn't the formula for average in general ([sum of all values]): ([number of values])? Maybe there is another definition for physics though.
I'm learning game development, and these videos have been fantastic in helping me understand the elements involved in the physics simulations that game engines use. Thanks!
I've always really loved Crash Course and this Physics adaption is something I've really been anticipating. I'm extremely excited for this series! Thank you Dr. Shini Somara and Crash Course!
Great! Physics show, yay! Also, I have to note something in this video is wrong, and most physics teacher get it really wrong: Physics is about making best model which fits situation. Velocity or speed is not real, this is something we use to describe reality. There is absolutely nothing real about physics. We just build models. Every good physicist know that his/her model has limits and ultimately wrong, because model is not nature. Physics is a science of making models, as good as we can.
-Gets pulled over by the cops- -pulls out notepad,calculator and Jimmy Neutron science- -argues with the cops with said science for about 15 minutes only to realize I was wrong- Next time I’ll just take the ticket thx 😓
TheBigAEC I believe PBS is american, while BBC is extremely british. Since the host for physics is british i thought i'd make a joke about that, seeing as the previous host was american.
when I was in high school I had some lousy teachers for many years, except for one I had in my sophomore year. She was fast paced like Dr Somara but she would always answer every question you had and would walk you through the whole process of how an equation came to be. I wish she hadn't retired early because then I would've actually learned physics in high school instead of losing all motivation by third lesson during my junior year when I had a very enthusiastic teacher who was probably the brightest scientist that my school had, but she had very little patience with people like me who were slow with numbers 😢
Camila Stefanie this sounds a lot like me..wait it is me...r u me? What's going on? AnWAY u read my mind, its the same thing for me...the second teacher has very little patience....and she probably hates me now because of my slow understanding and how slow I'm at math and stuff...sooo...yeah
The formula on 7:20 didn't look right to me. I would say this is the formula for the final velocity, not the average velocity. Correct me if I'm wrong!
Hey, Crash Course, this helps but I'm a Geography student & I watch ur show because it is interesting to know more about other subjects. How about u do a Crash Course Geography ?
Dr. Shini Somara, for the last equation why cant we just use the change in position over time to find the velocity? Why do we have to use the dispacement curve and the the defintion of acceleration?
It's because she made an error referring to the last equation as finding average velocity. It was FINAL VELOCITY she found, not average of the whole trip.
Thank you CrashCourse, it really helps a lot because it gives a general view of what I'm studying and keeps me concentrated long enough! Thanks Dr. Shini Somara!