Physics 68 Lagrangian Mechanics (8 of 25) Example: The Atwood Machine

In this video I will find the equation of kinematics of an atwood machine using the Lagrangian equation.

Next video in this series can be seen at:

[hasan]

Oh boy wish I knew lagrangian mechanics when I took my AP physics class this makes problems so much easier

[lengsourchea]

I like this a lot...you make it easier for my self study..Thank you

[wkblack]

Great! I tried deriving it on my own, and didn't use a l, basing the blocks off of the same x=0 starting point, so their positions w/ respect to time were x and -x. Seeing your method of x1=l+x shows that the l term drops out, as the Lagrangian is about change, not so much about initial conditions.

[ethannguyen]

I both love and hate how you can derive everything from a single differential equation. It’s insane.

[sujitgupta]

U rescued my life ..from engineering.
Sir plz do something about Hamiltonian also

[yohanefunsirani]

Very important and fruitful man in this world

[vaibhavnmete]

Arbitrary L could be taken as total length of string, so length corresponding to m1 would be l-x2 if we consider m2 lengh from pully x2.

[mkonongo_og]

Is this lecture you can't harvest the knowldege in anywhere, only from Michel, thank you more, you make me bright especially in Classical physics. I have do all my tutorials left by Sir in the class after watching lectures of Michel...

[pilot]

Great job! One question, When writing down the Potential Energy, since you set the ceiling to be at 0 (so x=0) and the x being positive in the down direction how is the P.E negative, since all g, m, x are positive?

[karenbolanos]

This is a great video, thanks for the explanation. But, I have a doubt: in what case you can say that the Euler-Lagrange equation is equal zero? I can`t understand that, because generrally this equation is equal to Fj, i.e the forces non derivable of a potential.

[alexturone]

i have a question, if we establish, X positive go down, m2*g*(l - x) must be negative,  but, m1*g*( x), why  is negative??

[surajsah]

Thanks sir a lot, you makes me easy to complete the examples

[collegemathematics]

Great teaching.. Whats the name of the prof. Please.. Does he have a lecture note or textbook?

[salikk]

This makes problems look extremely easy as compared to the traditional Newtonian style.

[anaeem]

l is the length of rod that's why x2= l-x

[cleisonarmandomanriqueagui]

*I guess that l is not an arbitrary variable .. i understand it more as it where the longitud of the rope*

[hecz]

At 2:23 you give m1 a potential energy of -mgx. I'm not seeing why this should be negative if +x is assigned in the downward direction and g is also positive.

[TejasKdB]

What to do when there are not conservative forces like friction involved? Since we can't define a POTENTIAL I assume we can't define a lagrangian and hence.... Can't solve using lagrangian mech?

[abhijithkv]

a = ((m1-m2)/(m1+m2+moment of inertia of the disc ))g . what about the moment of inertia ?

[samiulhaq]

Sir please make a video on the important viva questions on classical mechanics for PhD interviews... I will be very thankful to you.
Makes a video like by questioning and anserwrinh please....
Thanks for you kind help in advance