Uniform Circular Motion: Crash Course Physics #7

Did you know that centrifugal force isn't really a thing? I mean, it's a thing, it's just not real. In fact, physicists call it a "fictitious force." Mind blown yet? To explore this idea further, this week Shini sits down with us to discuss centripetal force, centrifugal force, and a few other bits of physics to help us understand uniform circular motion.
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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

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Great, now I lost my key.

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I lost my ignorance :)

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I use a Knife My key is safe

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That flying Hit my brother and now his gone. Lol i have no Brother.

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@@carmelogonzales5053 not any more

[@dezent]

She kept me totally focused for nine minutes and twenty six seconds and i learned lots of new stuffs i did not know before!. Really shows that you guys are getting more and more professional.

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Please god someone fix that Rubik's cube I'm dyin here

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+Holly Panetta I have bad news for you ;)

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+thelonelydirector :(

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Blame Hank, he's the one who started playing with the cube in a meeting and now it's forever that way. FOREVER!

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+thelonelydirector :(( my poor order-loving brain can't take this

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When I play rubic's cube sometimes I cheat it

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just an idea, you should have an app where you can compete in a quiz with a stranger based on the material from your videos. It would help learn better.

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quizup

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or quizizz

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so a review just do quizlet

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2:45 The fact that phys is a required course for Computer science majors with a concentration in game development and crash course incorporates video game references in these videos makes learning all the more enjoyable!

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Hank is looking good!

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+leein jeon Hank usually hosts the CCs that are filmed in Montana.

[@djbslectures]

Who the eff is Hank?

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DJBsLectures I hope this is the first video you watched on this channel.

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+drink15 store.dftba.com/collections/vlogbrothers/products/who-the-eff-is-hank-poster

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"We're just here to make sure the ride is safe, we're not responsible to clean up all the vomit after the ride is over" Bahahaha, I'm sure the engineers agree xD

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+Vectored Thrust That's the rocket builders motto

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Last video 5 years ago bruh 😃😅

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I just failed my ap test this week, really could have used this earlier rip

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+Yale Benson I mean... I usually know when I've failed an exam.

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+CrashCourse ya... Not answering half of it was my first clue

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Can't you re sit the test?! 😪

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+Dan Gilbert Learning sometimes helps .. just a thought

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This video wouldn't have helped you on the AP at all.

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Great video. I'm close to 70 and live in the US, but when I was her age, we pronounced about 73% percent of all those big words differently :-) , Love it. I could listen to this video a dozen times. (and might have to . . . and take notes)

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I am at the bottom of motivation atm and I have a physics/chemistry exam in 1.5 weeks. So nice to have easy "lectures" on youtube. Thank you guys!

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I remember when i was back in 8th grade i couldn't understand a thing she said. I jus thought she was one bad teacher with crash course. now in tenth grade, this is the most clear explanation i have found yet. Thanks!!

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No idea is original, everything stems from something. To brake it down the more you understand the basics, the easier all the new stuff gets. You can't have the newest phone with out starting with the Nokia brick A.K.A THE OG (the struggle was real).

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You spin me right round... Thank you for your time.

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😂 nice one 😂

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Circular motion was my favorite section of physics last year, awesome video!

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currently watching this 3 hours before my AP test. god bless your soul

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Bless you guys, this has practically saved my GPA. So much easier to understand than what's taught in school

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This will save me in the physics exam in 12 days

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+SotraEngine4 Sounds like you need a better physics class.

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SotraEngine4 same

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this will save me on the physics exam in 16 hours. and i have the flu.

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Why is Crash Course always awesome? Is there some quantifiable element?

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+James Craver CC Physics is 2.7 less quantum units of awesomeness than CC Government and Politics (no eagle punching is negative factor).

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+James Craver Now I know from where Kurzgesagt seeks for materials, haha

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Kurzgesagt is awesome!

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+Bananaman Agreed (I'm a patron with a bird profile pic; not actually affiliated with them)

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It smells like months of hard work Famm

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The key turning 'experiment' is basically how discus throwers don't knock out anyone standing beside/behind them.

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It's interesting to notice that as we go further into these videos, the explanations make more and more (intuitive) sense. That's is great course outline work, folks!

[@brennahasselmann8075]

I love that you explained how the variables in each equation made sense in reality, that's the one thing that was keeping me from understanding

[@ExplodingPinapple]

2:47 Oh hi there, Link! How are you?

[@zachariahfurlotte]

Hey guys, awesome videos ! You guys have been teaching me material non stop all the way from grade 10 Advanced Biology to first year university Psychology and I just wanted to thank you for all your dedication and hard work ! I just transferred from a BSc to BEng and am studying to become a Material Engineer so I'm taking several physics courses in the spring/summer and am exactly where you guys are right now(Video Wise) ! P.S. I think I've gotten almost all my friends to watch your vidoes if they need help ! :D Thanks for all the dedication guys !

[@christinarobyn9820]

I'm in university physics and these videos are incredibly helpful! Thank you

[@realmenchangediapers]

Why did I live to the age of 34 before I found out that centrifugal force doesn't exist??

[@Eveseptir]

+realmenchangediapers It exists relatively speaking.

[@HaydenHatTrick]

Yeah, I get annoyed when I try and explain physics to people and they refuse to use fictitious forces. Because "their not real" Actually, you can think of fictitious forces as forces experienced due to being confined to a surface during motion. Because that is an entire field of math in its own, simply using forces produced relative to the object on the confining surface is stupidly efficient and true to what you actually experience.

[@SidPhoenix2211]

i found that out in a Horrible Science book, when I was in sixth grade

[@tutocfproductions7065]

So if it doesn't exist, why do we build things based on it and they work perfectly?

[@h20falcon59]

we don't centrifugal is just a name we give the machines we base them on centripetal forces, if for instance centrifugal force did exist, we wouldn't be able keep satellites in orbit they would go further and further away from the earth, and those centrifugal machines, have an arm attached to a giant pole in the center for a reason. :)

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Damn these physics crash courses are super clear! I hope it'll help a lot of people struggling with their mechanics class :)

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You videos have helped me so much in Physics. I couldn't find any reliable, informative and yet interesting video like these ones. I can't thank you enough. I'm more than thankful to you. 😊😊😇😇

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@Dr. Shini Somara You're just the whole package. I could listen to you could talk physics for hours. :)

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man, you guys should have done this last year, it's literally perfect for AP physics review.

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She has the best hair of any Crash Course host, WAAAAAAAAY better than Craig from Crash Course politics.

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+Aaron Horrell What about Phil Plait

[@DistortedMatt]

Too bad this was posted after the AP Physics Mechanics test! Still a great video and I am happy that Crash Course isn't afraid of covering a math heavy subject like physics.

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please make crash course programming

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That'd be a dream. But VERY LONG

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+

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YES

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+

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We now have Crash Course Computer Science. That's pretty good

[@daroastftw7579]

Thank you so much! In our intro to uniform circular motion, we rushed through some derivations, and the concept wasn't really explained. Thank you for putting words to variables and numbers!

[@thegaspatthegateway]

thank you thank you for the visual representation! (color coding the variables / connecting the variables with a line was also a nice touch :) )

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CRASH COURSE IS IMPORTANT ALWAYS

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Overall great video and examples! thank you CC team! :)

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These are so great to watch after going through text! Great way to reinforce the information, thank you!

[@FrumpybutSuperSmart]

Everything in this one made sense! I think I'm learning things.

[@TheSYLOH]

"I'm getting dizzy just think about it" She said as she cut to a graphic of SPINNING GEARS.

[@buenchiko007]

this came at the right time to reinforce what i already knew about circular motion in a cool, graphical way for my exam tomorrow. Thanks for this upload!

[@shoeeey5319]

I love these videos, they're so useful for my exams! thank you!

[@Ashley__Elyse]

This video explained Uniform Circular Motion in nearly ten minutes better than my teacher in almost a week. Thank You!

[@thenellecornejo3724]

time to re-watch this 5 more times

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FINALLYYY I'VE BEEN WAITING FOR THISSS

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Hooray for the guy who ends up cleaning up all the vomit \ o /

[@tennicktenstyl]

Didn't understand anything, sugar still gathers in the center of my tea cup.

[@HaydenHatTrick]

That would be due to centripetal motion (a force going towards the center of rotation). The only difference is that the system is more complex.

[@samsonclement7604]

When you stir the cup, water is forced outward because of centrifugal force, the same sensation you get when riding a carousel. This makes the pressure higher towards the edge of the cup. Close to the bottom of the cup friction between the fluid and the cup forces the swirling motion of the water to slow down and this in turn makes it possible for the pressure difference to establish a current towards the center of the cup that is stronger than the centrifugal force.

[@yeet6764]

@@samsonclement7604 I thought she said centrifugal force doesn't exist

[@lukaschrismalikistars930]

This so helped me. I have a circular motion test in physics tomorrow and this really saved me.

[@lema1425]

after having no idea what’s been going on in physics for a week and having a test on this tomorrow, it just made complete sense.

[@ashleya1601]

We're just about to start this in class, HELPED SOOO MUCH!!!

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Hey there, thank you guys for these awesome videos!

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Hi this video was so amazing keep up the good work love you all so much

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These videos are amazing! Thank you

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"They knew a big part of space flight involved acceleration" -biggest understatement in history.

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So What is the REAL big part of space flight?

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So What is the REAL big part of space flight?

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Ahh, wish these physics topics were already finished lol, woudve helped so so much in my physics exam just like how much it has helped me in bio and chem! Found the biology 8402 igcse paper 1 so easy mostly because of CrashCourse!

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Wow, you're' the best! Thanks for the effort you put into the vid to make it so easy to understand

[@TheTrueTeX1]

Love the fact, that you took Link for the depiction! :D

[@Sentinalh]

That was a lot of math, but I think I got it. Also Shini is beautiful.

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Your eye contact is appreciable along with your stuff...it kept me focussed.

[@perpetualpolymath5961]

1.Lets prove a = v^2/r if v = (2 x pi x r)/T 2.v= (2 x pi x r)/T 3.using chain rule 4.dv/dr x dr/dt = dv/dt = a 5.therefore dv/dr x v = a 6.dv /dr = (2 x pi) / T 7.dv/dr x v = ((2 x pi)/T) x ((2x pi x r)/T) 8.dv/dr x v = (4 x pi^2 x r)/T^2 9.dv/dr x v = (((2 x pi x r) / T)^2 )/r 10.we know that v = (2 x pi x r) / T 11.therefore 12dv /dr x v = v^2 / r 13.hence 14.a = v^2/r 15. Q.E.D if anyone is confused at 9 a quick expansion shows that line 9 equals line 8.

[@saeedbaig4249]

"4.dv/dr x dr/dt = dv/dt = a 5.therefore dv/dr x v = a" I can't see the leap of logic u made from 4 to 5. When u say "dv/dr x v", r u saying that v is dr/dt? I that it v was dc/dt (where c is circumference).

[@perpetualpolymath5961]

Sideeq Mohammad Simple chain rule is at work here. dv/dr x dr/dt =dv/dt , think of it like the dr's cancelling but the actual proof for chain rule is quiet long. we know dr/dt is basically the rate of change in distance and we all know that is velocity.dr can be exchanged for dx here thus dr/dt = v hence dv/dr x v = dv/dt = a.

[@saeedbaig4249]

Mo Killem Ok Im familiar with chain rule now but, as an aside, shouldn't dr/dt=0? After all, dr/dt is the rate of change of the RADIUS with respect to time. But the length of the radius NEVER changes in uniform circular motion.

[@perpetualpolymath5961]

Sideeq Mohammad It doesnt change in magnitude however it changes in direction and hence it does have a rate of change.After all displacement is a vector.

[@saeedbaig4249]

Mo Killem O ok sanks 4 clearing dat up

[@LucasCamargosRamos]

1:21 I was pretty concentrated on the video and thought I was just about to pass out. Well played. 10/10.

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I love how they have the ‘Feynman lectures on Physics’ on the shelves. Great books.

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my most productive 10 minutes, thank you ~

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Boy, oh boy, I loved this video!

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glad these videos are clearer now

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1:22 the editing though

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Thank you for these videos!!

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I'm so glad they've sorted out the heights of the lights behind her, it's all my brain could focus on before!

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I am loving it

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I love this video!!!!

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Homegirl in the video is really beautiful and very well spoken

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+Harmony of Nature almost distracting

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+Harmony of Nature Dr. Shini Somara... I believe she's Indian.

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Amazing!!!

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Awesome video! I knew most of these concepts, but this video cleared it up a lot. Especially the whole centrifugal/pedal force thing.

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AWESOME!!!

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good understanding of concepts

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the link reference was so cool:).

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Physics aside the intro is LIT. Love this channel.

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I love your teaching......thank you so much

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Nice video, good work.

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Brilliant course with this one, and a very intelligent instructor. It's well broken down, and conceptually it just makes sense in under 10 minutes.

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amazing! can you teach the process for writing algorithms? I always wanted to learn how to do this in physics and Programing!

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Best channel for physics

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I swear I had to replay this one 4 times just to figure out what was the difference between the analogy of the car versus the key lol. I love watching things that make me go grab a pen lol.

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Fantastic explanation.

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thx for another awesomely ha bisky physics vid i love this so much

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very informative! !

[@Ray-ye8gz]

Honestly, those physics videos are really helping me out! In fact, A lot :-)But you need to repeat the video and focus a lot on what Shini is saying.

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Thank you Crash Course Physics.

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Crash Course for the win helping me study for physics.

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Brilliant explanation

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Hey, those rides are fun, not nauseating!! :P But yeah, they're intense. :)

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super helpful!

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These videos would have been so useful on Monday.

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Thanks you, thank you, thank you for this!!

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This video have cleared up my question about why the velocity is tangent to the circle. I'm satisfied. Though I feel like going insane 😂

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I am looking forward to the explanation for the Gravitational constant.

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very nyc video likes its a lot as it clarify me every thing

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oh yeah and please do momentum and angular velocity and angular momentum pleaseeeeeeee

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Great course👍 it helps me to understand the physics in english

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She is so good!

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They took notes! So much easier to understand, good job!