Lec 4 | 8.01 Physics I: Classical Mechanics, Fall 1999

[donaldinasweater]

I wish this guy was my physics prof :(.

[SmokeDankTrees]

Not only is this lecture informative, it's also entertaining.

[NganaJHone]

I am very happy to see the vidoe from you, hopefully the others also are happy for You 3D Kinematics - Free Falling Reference Frames

[Ondelendo]

Steady I Really Like This Video 3D Kinematics Free Falling Reference Frames

[bebeheuy]

Good, I like that you share this video, I wish success always 3D Kinematics - Free Falling Reference Frames

[willamricard]

Nice Video 3D Kinematics - Free Falling Reference Frames That You Share , So Very Nice Thanks You

[imegatrone]

I Really Like The Video From Your 3D Kinematics Free Falling Reference Frames

[bundawartini]

Your Video 3D Kinematics - Free Falling Reference Frames Is Very Useful Sharing

[anakmudajaman]

after i watched this video 3D Kinematics - Free Falling Reference Frames, my insight is very open because the video is very good to give information

[MrKonshias]

SUPERB, I FEEL PHYSICS IN ME,NIGHTMARES OF CLASSICAL MECHANICS AT NIGHT AND........MUCH MORE

[mdiem]

He is just too awesome; I can't handle it!

[ThunderKid]

Love how he changes the angle to 30 degrees at the 30 minute mark (plus or minus 30 seconds because no measurement is valid without an uncertainty!)

[Martcapt]

I never thought I'd laugh so hard on a Physics Class

[mdgreg]

Thanks for These.

[ssoo1982]

Sir thank you alot, you good teacher, i can understanding you very clear . Thanks again

[sahil89424]

after seeing these videos i got interest i physics

[SmokeDankTrees]

I wish he was my physics prof. He explains things very clearly and on top of that he proves his statements by making an experiment. Also, I enjoy how he ends his lectures...what a great teacher.

[Scurmicurv]

This particular lecture is a bit of an inspiration to me. I remember the first time I saw it; I saw the monkey execution and thought to myself that THAT is the kind of teacher I want to be.Don't know if I'm even near WL's league, but the students I've had so far do seem to appreciate having basic calculus explained in terms of chasing a mosquito around the room and the need for pinpointing its position exactly in order to shoot it down. Thanks to MIT and Walter Lewin for this!

[JpJangz]

hi sorry, but @7:14, i realize that when they are added up, it became v zero Sin alpha over 2g, whereby how do you do that?

And one more thing is that, since he took formula 3, why didn't him include V zero which is the first portion of the equation

Sorry...i am picking things up as a noob T.T

[cheeri0os]

@JpJangz He has: (Vosinα)^2/g - (Vosinα)^2/2g. The first fraction has a denominator of "g" and the second of "2g" so you multiply the first fraction by 2 to get a common denominator. This gives you 2(Vosinα)^2/2g - (Vosinα)^2/2g. For the numerators, 2(Vosinα)^2 - (Vosinα)^2 = Vosinα^2 ...over 2g denominator.

He did not include Vo because his initial velocity at the point of origin was 0.

[unknownPLfan]

"In high school you would say it's supposed to land there, bull man!"

[Xonk61]

On the monkey in the tree and the hunter, all in the freefall elevator... if the elevator has already been accelerating before the shot is fired, will the results be the same as if the elevator begins freefall at the time the shot is fired?

[anmoljawandha]

Gr8 lecture:D thx MIT!

[anmoljawandha]

Gr8 lecture:D thx MIT!

[EJNewbury]

I love the epicness of the monkey getting hit in the nuts at the end. lol *slow-mo* *RUMBLE-RUMBLE!*

[roarintheforest]

My Physics I professor was terrible - we would sit at his desk and mumble to himself for two hours straight. I passed my super difficult Mechanics exam thanks to MIT's brilliant lectures. :) MIT, thank you so much for uploading this.

[adnanisar]

Prof. Walter Lewin, you are a legend.

RIP Monkey :(

[6618594]

in my country i see this in Highschool :p easy shit.

[CRISNCHIPS12398]

I'm doing Year 12 Physics in Australia for my VCE this year, and this all makes sense! It would so awesome if I could study at MIT in the future.

[hizay]

He explains it so well. These are the best physics videos I've seen yet so far.

[ac7491]

No animals were harmed in the making of this film.

[0WhosthatGiRL9]

I actually enjoyed watching this lecture. Very helpful! Who knew Physics could be this interesting! O.o

[MrLOKILLO15]

Does anybody know if it is actually physically possible for a bullet, that has been shot up in the air, to come down with enough force to kill someone if the average bullet travels 817 feet per second?

[SoNDgs]

@MrLOKILLO15 Ignoring air resistance it will hit the ground at 817 feet per second

[MrLOKILLO15]

@SoNDgs Ok thanks for the help.

[sssss3841]

@MrLOKILLO15 busted by the mythbusters

[maxauto44e]

science is cruel....but neccesary; poor robert

[MrDogbert2]

I like his sandals.

[pankaj51281]

he is best he is the first one who really make physics look practical. i wish this kind of teaching methodoligies could be followed in our country too.(india)

[shemcristobal]

great lecture!

[HunterDX77M]

Wow, I have never seen a professor this enthusiastic about what he teaches. For a second there, I actually believed there was a monkey back there. LOL.

[arsenelupin123]

Robert got hit in the balls...

[katanakio]

Thanks MIT for the OCW , by the way , what's 26100 ? he ( Walter Lewin ) sometimes mentions

[MIT]

@katanakio That's the room in which this class took place. The building is 26, and the room is 100, so it's 26-100. MIT buildings are almost always referred to by a number instead of a name, and the numbers grow as you move out from the Infinite Corridor. When you are North, an "N" gets added to the number (as in N42). Northeast becomes "NE," etc. It can be very confusing to a person new to the MIT campus, but once you learn the system, you can find any building without checking a map.

[zuchchi]

@katanakio HALL OF PHYSICS IN mit HAS THIS NAME !

[katanakio]

Thanks MIT for the OCW , by the way , what's 26100 ? he ( Walter Lewin ) sometimes mentions

[jbabe521]

hahah i love how they slow-mo-ed it

[afghanplayr20]

LOL he told that guy at 34: 35 to " BE A MAN " he was scared

[afghanplayr20]

Y is it that no one asks questions ? are they allowed to ask questions in MIT ?

[xoxosparkle]

these videos are simply amazing, a godsend. perfect for my ap class.

i can only hope i have professors like this when i get to college.

[pfat0]

@thecomanche1 because that isn't the equation.

[mridularul1]

I wish if i could get a chance to study from him i could really have done wonders with him around. He's the best teacher I've ever seen in my life.God give him long life :)

[danrayson]

"WOAHH!! JACKPOT!!" Best lecturers around!

[andreirocks1992]

lol, slow motion

[bloomingdedalus]

I am truly surprised how many MIT students raised their hand for the same time when the question was asked between the time of a parabolic path launched with a uniform velocity from 30 and 60 degrees.

[Cabuncle]

and what was the uncertainty for the 6.14 meters he measured ? *gg+

[Taowhr]

Is it just me or did the ball hit the monkey in the balls?

[TGMRobotSanta]

these comments are serious business

[sonchand19]

dont mean to hurt..but we are taught all this in plus 1..before we get to coll..Im in IIT and in all collgs this is like prerequisite

[ab501lara]

damn iit.... u people get to iit without understanding any concepts... only problem splving is done... u people dont get the basics right.there is no demos done in india... but, in mit, this genius explains so beautifully that u get ur basics right.. how many people have got noble price studng in america(mit) and how many in iit.. so dont even compare ur plus 1 with wat is taught here..

[labitx]

Don't they do revisions? Its important to do revisions so your foundations are strong. Don't be too confident.

[GradiusCVK]

You say "we are all taught this in plus 1"... but sorry tard, in India only the top 15% of students even reach high school, never mind how many graduate. In the US, 85% graduate high school. So, you're being a douche because the top 15% of your country learns things a year or two before the entire population of the US? Judging by your misspelled retarded post, I assume you must be an Indian supergenius, relative to the rest of the country.

[Dual1ty]

haha you fuckin suck. I graduate from HS and Physics AP here is a fucking joke... Yeah 85% of the students graduate from HS but most of them are dumb as fuck

[thejugglenaut91]

you people really don't get it do you? Every(good) college course requires NO prerequisite knowledge. This way you can build everything up your way. If you're a good teacher than the student gets the whole picture. If you're a bad teacher, you require alot of material and so you don't explain everything all the time.

[19cohen]

"it always happens with robert" hahahaha

[weweallthewayhome]

i could listen to the man lecture all day, he's wonderful

[Kritarrista89]

"oh, my calculator was off. That's a detail."

this man is a genius

loooools

XD

[death2art]

A question to all americans here:

Do you learn this in college? Because here in Portugal we learn this in our 11th grade (2 years before college)

[gaucable]

Yeah I'm sure MIT is like another Portugal highschool....just think about it man....

[death2art]

I know MIT is much better than a Portuguese highschool, but i am serious. They teach this in the 11th grade here...

[gaucable]

Yeah u learn how to speak in kindergarden or wherever and than you have debate team where you do the same think. (hope there are debate teams in US cos its like in every movie:)

[ctcboater]

Unfortunately physics is not required for graduation in all (maybe any) US high schools. Heck, I don't think that even geometry or algebra are. US primary and secondary education are pretty pathetic.

When I entered RPI back in 1964, high school physics, chemistry and calculus were required courses for all applicants to the Engineering and Science schools. That appears not to be the case any more.

[TIGERSDFW]

I disagree, Just because calculus is not required doesn't mean the schools are poor, Average and below average students can not learn calculus and physics in a functional time period. So, putting them in the classes would only slow down those who may indeed become real engineers and scientists.

[KingFinger69]

u can learn it in 11th grade in america too..some people do...they get AP credit..and skip this course in highschool...other people take it...in high school..still..want to learn it again and take it in college...some people don't take it in high school..and take it for the first time in college...so...it all pretty much depends...i'm sure these students at MIT were just taking it again...to make sure they got all of the basical fundamentals down...

[death2art]

That is why american educational system is so confusing...

In Portugal, if you choose Science in Highschool you must have Math and 2 of these 3 Subjects (Physics, Biology and Descritive Geometry). And if you want to study Engennering you MUST have Physics

[Camisho]

I am learning this because of an interest in physics, not because of my school or anything. I'm not quite in 11th grade yet, but I'm taking physics when school starts. (considering that it is the Summer here)

I wish I lived in Portugal though, I get bored of the simplicity of what I am learning right now...

[CanisLupus1987]

why do you wish to live in Portugal?

[Camisho]

Well It doesn't have to be Portugal, any place with harder educational standards would be nice..

[MarijnStevens]

I know what you mean, but it all depend on you, pick up some books, start learning for your self, realise that education sometimes hold you down.

[TIGERSDFW]

Normally, this would be a 12th grade class for an advanced high school student,

[lorent123]

Yeah but i guess they have to do this revision... At least he goes through that fast

[Kosha2905]

@TIGERSDFW

Thing is, this is like an AP course in high school. Although he does go through it quicker, and with more detail, the curriculum is about the same. The course in the US, atleast in NY state is called AP Physics B (without Calc.) and I am currently taking it in 10th, although it's generally taken in 11th or 12th grade. So while it's not terribly advanced, it makes sense that a freshman college class would "review" this curriculum.

[labitx]

It is important to keep re-doing the basics (obviously at a faster pace) as basics are important foundations that you must grasp well, before you can build your more advanced concepts on top of it. So do not look down on basic concepts. Arrogance will only bound you for overconfidence and then failure.

[matharoofmaths]

you have hit the nail on the head i forgot the basics and now im in a hole whith little chance of escape

[thejugglenaut91]

Ok I learned mechanics in what seemed to be a beginner's course. It was the highest level at my (crappy) university. I'm transferring next semester to a killer physics department. Do you think I should pick up like Goldstein's or Symon's text or something to that effect and read it during next semester's work? Any suggestions for some good texts?

[jpaultel]

@thejugglenaut91: The answer requires a question. It is possible that there is a big gap to cover? Which text did you use in your last program? Fundamentals of Physics (Vol 1) by Resnick is a very good intermediate text. This is how I usually approach these problems: I go into a well stocked library and take a lot of time - hours - flipping through books and I eventually emerge with a tille or at most two that I feel comfortable reading and that I feel give me the concepts. The math later.

[mmmmmmmmmo]

poor monkey

[horntail140]

the x-component of the projectile motion doesn't accelerate if you neglect the air resistance (and possibly other resistance)

[opiumgland]

Right, but who said it does?

[agraver]

46:44

[WSA10]

Wow, a monkey! I've did this demonstration a few times myself but never had the idea of this kind of stuff like little monkey pal :D

[recyclingismylife]

does anyone know how to detemine the sign of g relative to the value given to g as a function of y? in other words, if g is positive in the positive y direction, is the sign positive or negative for g in the equation for y's position/velocity?

[opiumgland]

Not sure what u mean by "the sign of g". g's the magnitude of a force. Magnitudes are never negative. The sign you place in front of g in a given eq depends on the situation you're measuring. For time to apex, the eq obviously must yield a non-negative value. Set v(final)=0 and the eq is v(i)*sin(a)=g*t. Substituting -9.8 for g will give you a negative time for a>0, so you see why g isn't neg. For apex height, substitute v(i) with dy/dt, multiply both sides by dt and integrate accordingly.

[corneliaomir]

g isn't a force. Is an acceleration, it is a vector, and its sign depends on where do you choose your positive axes pointing to.

[opiumgland]

Wow what the hell was I smoking 2 months ago? hanks c.

[opiumgland]

Though I still say g is a magnitude and always positive. Using g as a vector involves giving it a direction and the common pitfall then is to substitute g in an equation with the number -9.8. The easiest way to think of it is that a is a vector and g its magnitude. An example is is freefall in a vacuum with 0 initial velocity. Without calculus the equation is v(t) = a*t. The acceleration is regarded as downward so the eq becomes v(t) = -g*t.

[vadimgrin]

Epic Monkey expirement.

[akabyl]

Отличный профессор, плохо, что у нас таких профессоров практически нет, пусть пример берут!!

[prateekkurkanji]

this was awesome

[prashantparikh]

This lecture is awesome, I understood it while it was being explained so clearly, I don't know about others but I'll definitely need to come back to this lecture a couple of times for a revision to be able to do these problems on my own

[jhonma1]

La física es expectacular.

[gamefreak759]

This guy is really good at what he does. This is of course due the demonstration after the lecture.

PHYSICS WORKS!

[sbarber317]

Physics is all about understanding I am currently going to school to get my physics degree Thanks for whomever posted it and I want to say thank you

[lamugr8]

Hi Im the student of KARACHI University, I found this very well explained. An energetic teacher

[moon22666]

Awesome. No doubt.

[iluvjiyongx3]

this is soooo cool!! man, physics is awesome! but poor robert. ^^

[iluvjiyongx3]

good teacher~~

[hangrry]

wittly practical! Mr. Lewis is funny

[newyorkairlines]

Agreed! Btw It is Walter Lewin not Lewis =)

[Rodrigofelipe777]

Awesome!!!

[cruxis7856]

this lecture was awesome!!

Those demonstrations are really cool too. You can actually SEE what he is talking about :D

[TEAMELFA]

lol

[chadwickneutron]

Fascinating lecture

[2Plankah]

Robert!!!! Nooooooo!!!!!!