Pulley Motion Example 1 - Engineering Dynamics

An introductory example problem determining velocities and accelerations of masses connected together by a pulley system.

[@ericaleonardi5776]

i love this guy's intro. It actually makes me want to study structures hahaha just to hear it

[@SeanDaNerd]

This was excellent. Setting up the datum and equations before solving has been tricky for me and my professor's tutelage just wasn't getting through. Thank you.

[@stephanosphilippou1300]

When it comes to education i am very picky. I just have to say that you're one of thebest out there. Thanks a lot for the time you have taken to prepare this and i hope to see you cover more topics related to mech.eng .

[@troyjones3715]

You sir are a champion and you deserve a bigger platform...

[@robinc5083]

Well explained! Sure you're helping a lot of desperate students! Thank you!

[@jasonegay7447]

You've really helped clear up this concept of pulleys for me. Thanks a ton!!!!

[@pinkcherry11]

You are amazing! I already loved dynamics but you make it so approachable and fun!!! thanks :)

[@meedo613]

that energy man :) Thank you for this example

[@czeckeredcat]

LOL'd at the abrupt cutoff at the end: "Structure FRRR!"

[@masooncap9769]

you teach this so much better than my professor, thank you

[@IQ-rl2wx]

These videos helped me a lot through university

[@NaimishBaranwal]

excellent man!!! one question clear all doubts.

[@project-moe]

literal beautiful video, subscribed

[@juni172]

very well explained, thank you!

[@nicenow25]

That's what we need msn enthusiastic teachers!!!

[@droppinhammerz]

this was really helpful! thanks!!

[@deekaye5735]

thank youuuu verry muchh. this answers my questionsss i love this

[@arunavamajumder6823]

Thanks man. That was awesome

[@aliangori]

You are a great tutor

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[@nbolt75]

Thanks for the help !

[@EpicPlayer954]

Crystal clear I can't thank you enough

[@structurefree]

Thank you!

[@fiveguysmenifee1513]

Great content!

[@oscarrinn]

I was a little confused about the equation that was derived for the second cable but then I remembered that what was outlined in red would be treated as a constant and we could exclude it.

[@ing.erickosorio2887]

Hi Oscar, if you don't have the answer yet. What's going on it's that's he's defining constant lengths and variable lengths, if you think about it, in reality the cables will stretch but that only means that certain parts as far as lengths is concerned will be the same and some will change length, but that's all based on the reference lines the has established. Now the red part of the cable your talking about will remain the same length no matter what, that's why it's taken as constant, since that cable is attached to 2 fixed points. I hope that helps.

[@symbionictitan4074]

life saver, Subscribed.

[@comicstwisted]

Great explanation

[@austinbeckd]

That was actually very clear and informative.

[@danishphysics9769]

what is the acceleration of two masses block when their are two pulleys and two strings.one string is connect to the one pulley and this one pulley on the inclined plane

[@AloneGalaxy88]

Thanks man :)

[@irvinrayados93]

Wich program do you use ? Excelent videos !

[@structurefree]

i use camtasia

[@RECrush16]

how could sm is changing length if the motor and the pully next to it are fixed?

[@structurefree]

The point m on the rope represents the motor

[@paulotago8603]

Quality mate.

[@noreaction1]

How does changing the angle of the incoming rope and outgoing rope at one pulley change the tension of the rope at that pulley? For example if the angle is 270 did not degrees as opposed to 360 degrees how does that change the tension? What if the angle is 180 degree as opposed to 360 degrees?

[@halehallamehhaery1803]

Hi, distance between pulley and the motor on the ground is fixed why you considered S_M?

[@vegamario7543]

thank you kind sir

[@batterflyfury]

thanks very much. ^_^

[@danese1636]

Fucking hell man... I wish I watched this video when I was taking Mechanical Dynamics 3 semesters ago D: Excellent video!

[@smtghosh619]

This was really helpful ❤️❤️

[@structurefree]

So glad it still helps!

[@mba2ceo]

Genius !!! VERY well explained !!!

[@structurefree]

You are too kind!

[@mba2ceo]

@@structurefree the only thing I would change the MOTOR reference before the redirect for symmetry :)

[@faiyadking2932]

How did u get 2Sb for the second equation?

[@l.rosemcsherry7621]

do you not count the cable lengths that are above the datum? like the pi(r) of the pulleys that are used for the datum?

[@structurefree]

I try to think of calculating the cable length from particle to particle. Some of those segments above the length are constant so they get lumped in to the constant.

[@BrazitodeWawa]

what's up with them structural dynamics videos? you only recorded the easy part..

[@MsMizlicious]

what about the distance on the right side of point M? Since M moves, that distance would have to change

[@project-moe]

M is a variable, kinda like how u set "some distance x away", so it is accounted for

[@mustafahasan6549]

I am confused, shouldnt the length of rope between the pulley and the motor be constant? why did you denote it as Sm?

[@shoukry8413]

thanks man

[@structurefree]

+Tarek Shoukry you're welcome!

[@ryujinryuk]

i dont understand why u consider sm while its indeed constant . can someone explain ?

[@Rycamcam]

I thought the same thing. The Sm length is constant -- the pulley and motor are both attached to the ground, thus stationary, thus constant. It's a constant, he just made a mistake

[@matildaho581]

thanks homie this was actually mad helpful :) :) hopefully it was helpful enough so that I dont fail out of engineering school rofl lol :|

[@Chloholio]

lol the inflection in your voice sounds like Sal Khan

[@annrufino4694]

lodi..tanx

[@hjalmarschacht2559]

Great example and an excellent description of the solution. Well done! Oh ... curb your enthusiasm. It may be cathcy.

[@Patar141]

The distance between the motor and bottom pulley are constant, I assume they are fixed. So how can you say s_m changes in distance? The distance will always be the same, so it would be treated as a constant.

[@kuenlai9736]

Late reply, but you still need a point for the motor to add into the length equation with Sb.

[@Iscrnd]

It is not a constant because he chose the reference of point M instead of the motor, and since point m is a point on the cable, and the cable is moving, point m is not a constant. Had he chosen Sm as a reference to the actual motor, you would be correct, but he chose a point on the cable instead which allows him to consider it as not constant

[@salsamancer]

Just ignore the motor and imagine that the point M is being held by somebody and being pulled. It's the same thing in concept.

[@ellyvatedaf]

LEARNEHHH

[@nomad8723]

thuglyfe

[@andrewbudiman1310]

definitely puesdo physics, alot of bookkeeping and less problem solving

[@emery5581]

I agree, good way of putting it. I just posted my opinion on this "presentation", look it up among the replies.

[@ShiyaRam8740]

Bakwas

[@emery5581]

This is not quite on an undergraduate level. Grade twelve, I would think. And even at that, you over complicate the solution. I tend to agree with the opinion of one of the commentators, "too much bookkeeping not enough physics". Teaching physics is about recognizing principles and getting solutions efficiently, not by "here you go, do this , do that, substitute here and there, use this formula or that formula".... This problem of the pulleys can be solved in one's mind without actually writing anything, the following is a guide: A downward shift in position in either of the moving pulleys will require an extra feed of rope length double the change in position. This is obvious at first sight. Therefore block A displacement is half of block B displacement which is half of the motor feed. Therefore the displacement ratio is 4 at block A, 2 at block B, with respect to motor feed.. Now, taking derivatives will maintain this ratio of the displacement maps, whatever they might be, so the rest of the problem is also pretty obvious. One more thing, if block A should weigh more than twice than block B, the system could not function....so, unless you place the proper restriction on the weights, you can not solve.