Lec 3 | 8.01 Physics I: Classical Mechanics, Fall 1999

[poetdragon]

Physics work!!!!

[iv54]

this is really cool im watchin this along with my college physics class tohelp ensure i defff getan a. i learned most of thisstuff in high school though. but im an engineerong major and im getting a free MIT education :)

[ollobrains1]

171k visitors

[stavrospod]

really great..and the last 4 minutes were the best..

[howincrediblyshit]

Cool, with these videos i can finally get a REAL education. It is almost like stealing.

[redrum41987]

169,000 viewer!

[saraniu009]

the cross product |a||b|sin(theta) must be larger than zero.

[leeyihlun19940520]

can someone answer me this question

is he talking about the right hand rule when referring to the corkscrew?

just like the ones we learned in electricity?

[taimoor722]

@leeyihlun19940520 yes



[TheLoneDevil]

@leeyihlun19940520 - Yes, where your four fingers represent the rotation of vector "A", your thumb is the cross-product vector.

[TrinhLoretacs15]

naja ich hab was unanständiges entdeckt

[3llay]

i wish my professor was like that

[mdiem]

I have to content myself with the fact that I will never be as cool as this guy. :-)

[goldenate]

As soon as he starts talking in three dimensions, I'm lost.

[probowler94]

11 people can go fuck themselves

[alex10163]

@Danelawz The cross product gives us a "Vector" which is perpendicular to the given vectors, in our case "A"&"B". One thing to notice is that the cross product works ONLY in 3D Vectors. U can NOT use the cross product in 2D Vectors. The Dot product is a scalar quantity nd u use it to find out the angle between two vectors. If two vectors are perpendicular to each other then "θ= 90". "cos θ" is then "0". according to our formula it says: A.B= lAl lBl cos θ = 0 WHEN A nd B are perpendicular.

[wittenberg5]

"the bad news today is there will be quite a bit of math" wait this is MIT hes at right?!

[Palmakoy]

Vrooooomb, Vrooooooooooomb, Vrooooooooooomb

his dots sound like Nascars lol

[NE5pats]

awesome!

[purplebluebirds]

"I have an apple-

not an apple...

This is a tomato-

not a tomato

It's a potato!"

[Falewick]

@purplebluebirds His brain is dealing with physics, not fruit and vegetables. God I laughed though...

[proslice56]

wouldnt the parabolic curve explain this better

[trentWHY]

lost me at 2:00

[jrowley47]

There is an error around 22:20. It should be Cx - Cy + Cz.

[holbansimona]

@jrowley47 there is no error, he just introduced the minus sign into the bracket

[Yakeyglee]

@jrowley47 No, because the value of C_y already takes care of the signs.

[liju87philip]

Now that's called passion for physics. Physics works!!

[jadx99]

Epic

[barnettb901]

his cross product is too confusing, just do it as a determinant

[stewitr]

His dotted lines are amazing.

[baktru]

2600 is the lecture room number...

[diablo9873]

what is 26100??????

he keeps saying this no. repeatedly..

[wowzabowza123]

@diablo9873 26100 is the lecture hall they are in

[anuarag67]

This kind of lecture given in MIT? I am surprised ! this is high school stuffs.....

[AleifrLeifrson]

@anuarag67

I don't know what university you went to, but where I go, we also learned high school stuff in the beginning.

[MrPushp12]

@AleifrLeifrson because of tough competion we have to do theese things in high school thoroughly..

[MrMcj87]

Although I'm a filmmaking student and it's entirely maths that I'll probably never ever have to use in my life, I can't help but watch his lectures, he's just too damn good a teacher and makes every little figure fascinating.

btw, don't watch the vid from 31:05 if you haven't watched from the start or you might go kabooze *g*

[fleminem1]

i think i got overly excited when the golf ball landed right in the funnel lmao !

[robleclerc]

What an absolutely brilliant educator! Such CLEAR explanations and great empathy for the students. Perhaps I could have been a great mathematician of physicist had been my professor.

[Yami7761]

U R GREAT

[ac7491]

His wackiness is so refreshing.

[junior1984able]

i would call the vector," x component, y component, z component if it were 3d" better than getting confused , my opinion

[junior1984able]

i f the object 's initial velocity is 0 , then the equation looks something like vf^2= 2ad

for the disance formula: d=(vf/2)change in time

[junior1984able]

the final velocity of somethin in constant motion = the inital velocity of it + a (change in time)

or vf^2 +vi^2 + 2ad

[JmSantos78]

@KlassicStrat72 I suppose you mean a 90º angle. It's actually a bit over 90º, but not much. It's easy when you get the hang of it.

[Zee96969696]

well, the dot product i think is getting through to my head, but the x product I don't fully understand. one thing that worries me is all those equaions, i just hope i'll be able to learn them before exam time

[mariomaruf]

He turned "There is no x acceleration." into a 10-minute experiment.

[wreynolds1995]

@mariomaruf 3-minute. Not 10-minute.

[loopdeloop17]

His cross product he forgot to subtract the second (Cz) term.

[loopdeloop17]

@loopdeloop17 Cy not Cz

[ton321]

shit, I think I once understood this stuff, but he blew my mind!

[juakawillowsbrain]

One observation (24:32 min): AxB is a vector, |A||B|sin(theta) is a scalar... the equality only holds if you take |AxB| instead of AxB

[CliveSinclairZX]

3 down.. way more to go.

[Gsapc0ntrab]

This video is fantastic I wish I would have found this earlier

[aaaa1]

I loved physics for scientists and engineers 1, pretty hard for a freshman class but worth it.

[Sinagitarius]

Anybody knows how he does the dotted lines in one swing of his arm?

[RICARDOTORRES1985]

does anybody know where can i download the subtitles of this lectures?

[Sinagitarius]

@RICARDOTORRES1985 Dude there's a transcript beside the description of the video.

[elchafa]

What does 8.01 mean?

[KingRobbStark]

@elchafa In MIT the numbers is what is used to denote a subject. 8.01 in this case is referring to Physics.

[limerick2090]

those dotted lines are so cool

[killkill0]

He looks like a mad scientist.

[MrTechnoAlex]

nice egg.

[ssrider7]

this r real profesors...u can see his crazy phisycs mind.His life is phisycs,and he wanna learn as more people he can...pretty amaizing.this guy is a hero for me.

[aripnurwana]

It's sound very Excellent Lectures, I am Learning now. and I love him so much. God Bless you dear Profesor, Arip Nurahman from Indonesia

[GuidoPerdomo]

so cool how he marks with dots..

[days0901]

wonderful resource on You tube,his lecture really helped me a lot.ha-ha

[sajidullah]

This professor 'wants' to teach. Others are just doing their jobs.

[jackshay01]

why does he have an egg on his pocket?

[23SuS23]

I love the type of chalk they use, lol

[ditaelita]

he is very funny and makes physics is fun

[ditaelita]

he is very funny and makes physics is fun

[LogicalFlawDetector]

This is not even the best MIT class. This is just one of the many introductory classes in physics. This is the least demanding class intended for engineering majors and non-science majors.

There is another class intended for physics majors. It uses the book "Introduction to Mechanics" by Kleppner. That is even more bad ass than this one.

The same with Calculus classes. What they post on the net for free are the least demanding ones.

[gulloogtg]

@LogicalFlawDetector

My frnd, this is an EASY class, everywhere. if u see 8.02, IT IS KICK ASS.

where do they teach with that book? at mit?

[LogicalFlawDetector]

@gulloogtg

Look up the MIT OCW site -- all the variations of 8.01. Check the syllabus tab for every course, you will find the book. But there aren't free lectures for that class, obviously. And 8.02 is also very easy.

[TenForExecution]

This guy is great.

What kind of qualifications would you need to get into a uni like MIT? I live in scotland and thus may need a grade translation to Highers/Adv. Highers.

[virusnyak]

building?

[milpitas1985]

I just figured out vector addition:)

[musyun1]

Great instructor, he teach very good.

[johnAshpool]

teaching undergraduates = teaching morons

[thejugglenaut91]

so you were once a moron? When did you grow out of your moronic ways? even more so, when in your undergraduate career did you realize that you were in fact a moron?

[johnAshpool]

Yes, I was. I grew out of it in graduate school. I didn't realize I was a moron when I was undergraduate because morons normally don't realize they are morons. It was only after teaching undergraduates for 3 years that I realized they are, in fact, morons.

[crudvelch]

he is clint eastwood, right? .. :P:P

[asafefraim]

49:15

physics works! see you Wednesday.

[JustWonderingHowToDo]

He's Dutch isn't he?

[Whopzer]

@JustWonderingHowToDo: Ja, he is indeed dutch.

[holyender515]

20:00

[MrKBentley]

I wish I could work a piece of chalk like him!

[JmSantos78]

@MrKBentley Just use the chalk in an angle a bit over 90º, but not much. It's easy when you get the hang of it.

[krillansavillan]

great refresher!

[femtophysiker]

This prof. is funny and reminds my college time...Loved physics...

[kfish117]

honestly. I could not think of a better physics lector. I go to MIT now and was going to take 8.02 Physics electricity and magnetism, but he doesn't lecture anymore. Now I'm studying for the exam to pass out of 8.02.

[sixteenfourty]

physics works.

[RylyC]

@sixteenfourty see you wednesday.

[philotaaveti]

im learning

[naguelles]

"my g is always positive"... what a cool homey he is ;-)

[Mathikins]

"...if you do that i will KILL you!!! you will always always work in what we call the right hand system..."

i love his passion in his lectures lol ;D

[ElizabethAGreene]

@Mathikins : Careful, we know he has a gun from 8.01 Lec 2!

[ClaireNJay]

i learnt this in my as physics class...

[rtoindru]

Minute: 41:28 He says the velocity in X axis is constant but if alpha changes should it not change?

He says the velocity doesnt vary with time in horizontal X axis. But velocity is defined as vcos(alpha) and with time the angle alpha and hence velocity in horizontal shud change rite? why doesnt it?

[pathologicalpoet]

the alpha in v cos(alpha) he wrote on blackboard was measured at the start time hence not time dependent. the reason why velocity along x doesn't change is that acceleration along x is zero since the only force is gravity which is vertical. it is true that at subsequent time alpha will change but then v will also change and these change together will be such that the new vcos(alpha) will stay constant.

[rtoindru]

Yeah I kind of figured that out in time... alfa is the angle of projection and it doesnt change ... so your partially right not fully.

Originally I thought alfa was the tangential angle of the parabolic path! Hence the confusion

[pathologicalpoet]

When I said that at subsequent times alpha changes I obviously meant the direction of the velocity vector with the horizontal axis so I guess I didn't make any incorrect statements.

[nasirk70ahmad]

Alpha is the incident angle so it is always constant i.e The angle at which projectile was fired/thrown in space. thus Horizontal component is conatant.

[elementary69]

FIRST NEWTON LAW

[wyz135]

What does the 26.100 he keep saying means??

[thermalCat]

i think thats the 'name' of the room. he uses it when talking about an observer who is in the room, but not standing on the table with him.

Very nice video !

[GiveItOrLoseIt]

"It's like going to the dentist"....LOL

[BaloneyX]

Thanks for the lesson, the fried egg on his shirt makes me lol too :D

[iiimtf44]

why do american people say math, british peope say maths? is that a competition? like

[AWSmith1955]

at 26.10

I have an apple, Not an apple this is a TOMATO, not a tomato its a POTATO!!

[lordennis01]

This man is a genius, not in the context of the information, but in the context of the manner of his presenting the information. I have yet to see a professor express it with as much diligence as he.

[Cplex702]

fastforward the lecture and watch the last 3 minutes. That's the fun'er' part =]

[PianoWallaby]

Thanks for posting this!

[kavoos1000]

he is the best

[davidablair]

What's the "twenty six one hundred" he kept mentioning means?

Probably the classroom they are sitting in?

[newyorkairlines]

Ya that is probably the room. Every building is numbered at MIT, and 100 means its room 00 on the first floor.

[wyz135]

What's the "twenty six one hundred" he kept mentioning means?

[indagun]

really really good lecturer

[forsakendreamer]

I love your videos!  It gives me something interesting to watch when I am bored! Thank you very much for posting them online!

[dondean517]

Thank you so much for posting this stuff.

[swingsetbucket]

This stuff rules!

[smileyellowkat]

awesome lecture...!!!

very easy to understand!!!

nice & clear!!!! luv it!!

[sbee00]

best prof i have ever had, hands down.

[k9iou]

THIS CLASS WAS VERY GOOD !!!

[Anonz3]

hes crazy good at drawing graphs. I couldn't even copy his graphs into my notes because they're so exact!

[merabharatmahaniam]

Kudos !!!!!!!!!!!!!!!

Can I save this to my hard disk and burn this into video lectures to a separate device so that I can relish "virtual Physics" environment?

[Anonz3]

yeah, they give a url in the video description where you can download the videos

[BrianC589]

I really enjoy Dr. Lewin's lectures! Please continue to post more! Thank you.