Lec 21 | 8.01 Physics I: Classical Mechanics, Fall 1999

[msjessypp]

This is a great video

[ienjoyapples]

i think this must be a 6 AM class, cause the student look like they're about to fall asleep despite the stimulating lecture.

[EgoSumIndigentia]

The reason that device at the end of the lecture was able to turn around the other way is because when Prof. Lewin spun it, the device was built in such a way that it would rotate both polarly and azimuthally; so it has a certain amount of vibrational energy up and down as well as around. When the processional rotational energy has been "used up", there is still enough azimuthal vibration to provide the torque needed to rotate the device in the opposite direction, causing the effect shown here

[Dave67004]

Definitely the hardest 8.01 lecture yet; I'll have to go over a lot of that again...

[leaderofasla]

with this video, i think i don't need to attend my lecture

[1hotkidplusanother1]

i searched what goes around comes around like a hula hoop? wtf

[RazorCallahan2424]

MIT is epic!

[Ankur834]

I like this all MIT's VIdeo really, I enhjoyed this all physics Video's...Thank you for this all...

[scinsight]

pr.Lewin makes mechanical physics so easy, you just grasp it right away.God bless him.

thank you so much MIT the best university ever.

[hgfuhgvg]

where is the next video lecture in this series? (he mentions 5 lectures dealing with these concepts).

[hgfuhgvg]

yes, please tell me about the dotted lines.. I had a teacher in school who did that.. I need to learn as I constantly need to draw dotted lines at work (with a marker).. please someone tell me the secret.

[freethisone]

please help, if i have a system of objects, large planet sized objects. and they moving trough space, but then interact with another system of objects that effect its angular momentum, then the orbit of these object cannot be conserved, due to a tourque place on the system by the sun. therefore these are degenarating orbits, and all planets in a system will become a comet with steep angular momentum to the sun. and again therefore the eliptical orbits are caused by there degeneration of orbit.

[anaki71]

sick might have helped a week ago lol.. B= magnetic field strength A= area of coil I= Current n= number of coils

[mridularul1]

@anaki71 sorry i wrote the wrong equation :P

[anaki71]

can anyone tell me if this is a formula to find torque?? t=BAIN cos(theata)

[Gainsborough89]

damn.. content of the lecture aside, HOW DOES HE MAKE THE DOTTED LINES ON THE BLACKBOARD WITH THE CHALK LIKE THAT?? @_@

[khwezi1986]

@Gainsborough89

easy you point the head of the chalk in the direction on which you r going or instead of pulling the chalk down with its tip facing up you push it down with the tip of the chalk facing down hope am making sense oh make sure you move fast and apply pressure on the other end.

[MrTreasoner]

@Gainsborough89 Hold the chalk in an inclined way against the board and it should touch the tip...and slowly try to drag it ull get it..practice it ull get better..:D

[anirdix]

mit has really shown its greatness by making such a bold effort

[Deborah8678]

Hey, can anyone think of what the period would be, if b = 0 for the case of the ruler oscillating around point P? From the equation it follows that the period would be infinity...

[quifred]

@Deborah8678 If b=0 it means the ruler would be rotating around its center of gravity. In this case there would be no net torque meaning that the ruler would continue to rotate in a circular fashion. Or in other words the period is infinite.

[omartron]

wheres he from?

[lennyprankster]

00.26



[partonfilaton]

so what was the deal with the piece of plastic in the end?

[HUTINAK]

I am lost...which one was the Sun?

[IdRatherBeCubing]

This is great, it actually makes sense since he gives examples unlike my professor

[edudanos]

I have to say that I'm very proud of my University. This class is very likely to the one i got on Physics 1. I attend to Universidad de Buenos Aires (Argentina) and, in spite of the great technology the MIT has, the teaching qualities are very similar.

[fbellino89]

@edudanos hola soy de buenos aires, que estudias en la uba?? en que facultad tuviste clases parecidas a estas??? exactas o ingenieria?? que profesor? yo estudio ingenieria en la matanza pero estoy pensando en cambiarme,

[dechicken]

wow that chick is sexy at 12:00. =)

[lennyprankster]

@dechicken dont know what are u talking about..............are you an idiot of talking such non sense thngs

[Shazaaming]

Anyone know the "trick" to 47:00 spinning plastic toy that reverses direction?

[flyingpatte]

I don't know how the plastic toy is working, but I guess that it starts wobbling when you spin it in the "wrong" direction. When it stops it still has energy becuase it's wobbling and becuase of this wobbling and the shape of it, it will start to rotate in the other direction. Probably this isn't the best explanation, but it is my rough guess.

[cswanson3]

First here are the properties of the object

1. curved base has two different radi

2. the axes of symmetry of the celt must be skewed slightly from its principal axes of inertia

3. there is a different distribution of mass about each of the two horizontal axes of inertia

The toy is called a rattleback but are also known as an anagyre, celt, Celtic stone, rattlerock, spin bar, or wobble stone

[cswanson3]

Answer: The spin-reversal motion follows from the growth of instabilities on rotation axes, that are rolling (on the main axis) and pitching (on the crosswise axis).

Then there is an asymmetry in the mass distribution with respect to the plane formed by the pitching and the vertical axes, a coupling of these two instabilities arises; the asymmetry in mass deviates the rattleback when pitching, which will create some rolling.The amplified mode differs depending on the spin direction

[tomking91]

He lost me at "last lecture" :S

[TommeyLeeReed]

I like this, Dont have to pay for it now.

[nhojmabon]

I agree, open courseware is the best idea ever. Thankyou MIT, thankyou Walter.

[anirdix]

mit has shown its greatness by making such an effort