Basics of Linear Momentum: Part 1 [Fluid Mechanics #27]

[@AS-fm5ew]

Veey simple and easy explanation..thnx buddy

[@yiling3582]

i guess it would be more appropriate to describe the resultant force as the time rate change of linear momentum, f=ma assumed that mass is not changing and dropped out of the derivative. Apparently density could be changing therefore f=V*d(m)/d(t)+ma

[@magaldi_espresso]

Very helpful, thanks from Brazil

[@dulcetdicembre]

LIFESAVER, keep it up!

[@Nazmokabazaar]

which pens do you use ? 😃😃

[@randomwurst6519]

Sharpie

[@Acatchy]

Fine point sharpie

[@markkerollos]

Great. All it needs is SI units :P

[@Napsmack]

These videos are great "recaps" to my fluid mechanics class! I wish "nukies" didn't have to take fluid mechanics haha.

[@SGF08Y]

Surely the reaction force of the bolts is in the opposite direction to which you have drawn? The free jet generates thrust meaning the pipework wants to move to the left, thus the reaction force acts towards the right.

[@BenNBuilds]

It takes force to hold the nozzle on. there is more pressure behind it than in front of it. The pressure is constant everywhere behind the nozzle. Any thrust generated comes from the fluid moving through the hose, most of the "thrust" you feel from a hose is because its curled. This is not a rocket engine, there is no divergent section where the fluid is sped up as the pressure is reduced, which is what generates that kind of thrust

[@amrshehab7019]

@@BenNBuilds but why a fire man need to exert a force that is in the direction of the stream not the opposite ?

[@BenNBuilds]

@@amrshehab7019 Thats the reaction force.

[@amrshehab7019]

@@BenNBuilds this reaction force acts on the nozzle and we are studying the nozzle not the fireman so what i understand that this force we are calculating is the reaction force that is needed to hold the nozzle in its place what is wrong with what i understand

[@MrSkyman789]

I wish my teacher could explain it like you did

[@annal5751]

That was great ! thank u so much :)

[@apoorvshrivastav6979]

Why pressure is Zero at that point ? Please Explain

[@nitzangoldreich3652]

some one knowes the pen he is using ?

[@randomwurst6519]

Sharpie

[@drakbrid09]

You are so awesome!!!!! Thank you so much :)

[@kobi8231]

Jackie?! lol.

[@drakbrid09]

hahhaha yeap that was me on fluids lol

[@h.h.c466]

The pi/4 is a bit confusing, mabe use radius instead.

[@h.h.c466]

​@quique182I meant that better to choose a unit radius instead of diameter, or if to stay with these arbitrary units, just mention a side step (dia/2), so that one does not confuse unit manipulation dia/2 = radius with formula representation r^2*pi. r^2/4*pi is not seen as original representation and one can lose track of what is unit manipulation and what formula. But that is my opinion, just wanted to state my issue correctly. Of course this is a really #minor# step, but when it gets more complicated one can loose focus of what is new formula and what not. Great work by the way.

[@Lee-xw5cf]

Do you any more questions related to this?

[@vishalojha1745]

Pogchamp yes

[@sabrihamad]

very useful. thanks

[@sohamurali6949]

why is the pressure at free jet equals zero

[@bonnax07]

julius umali i don't think the answer will be the same if the absolute pressures will be used.

[@metalhead66650]

+Soha Murali That is because you are using gage pressure, as Julius pointed out. If you were using the absolute pressure, you would have to have a force due to that coming from the right where the nozzle opens into the outside. If you do the calculation, it would come out to be the same as the way he is working this out.

[@eisleyism]

Newton's 3rd Law.

[@imstudentxxxxx]

should be volume/time = velocity x area

[@Hugo2284]

I really like the way you teach fluids dynamics. I have a few doubts in a problem of linear momentum in a pipe. My question is... Is there a chance to get some help from you to get the problem solved? I'd be so geatful if you do. Greetings¡

[@oxstorm644]

would it not be simpler just to write 'a' as 'v/t'? i'm from the uk - never come across 'd' other than distance

[@Goaterd]

"d/dt", is the notation to represent a derivative with respect to time. Unless you have a very different notation, then simply writing "v/t" would be quite different.

[@wahidulislam130]

each time you say "pressure is zero for a free jet", just add the term "gauge" before the word pressure. Since zero pressure is vacuum.

[@salvastalker]

By default, all pressures are "relative pressure" when solving problems. At least, I always found it like that.

[@KumarHemjeet]

it's gauge he is talking about

[@chantsztsung7939]

thanks

[@eisleyism]

That's not the "linear momentum flow" thats the derivative of the linear momentum flow.

[@manandianupama4446]

Thanks ...u sound like flash to me

[@khaiz911]

Q = V/s = VA??

[@SimmySigma]

thank you! :D lol

[@Hockeyrocks229]

CHRIST almighty THANK YOU