greetings sir. your amazing videos and your teaching skills are really impressive and gladly i understand all of your explanations..you've helped me a lot!! god bless you.. (from mechanical student)
Hey prof, funny thing! Year ago I watched your video because I was redirected from another channel that credit you. Today I'm here because I'm in a quest for good subject for my assignment from programming class I'm taking (need to compare results from theory and numerical analysis/primitive simulation about some effect). I see you have put annotation with correction and I could't help myself to not notice that it shows "x Pa = y Pa" instead of "x Pa = y atm". I know that I'm nitpicking but I find it bizarrely funny how I'm spotting these.
Hi. I have been struggling about why not taking the whole area of the split sphere. Now I understand is due to the vertical component of the force and equivalent area. It makes total sense! Great video, thank u!! 👍
4:05 , the pressure inside droplet is because of fluids resistance against compression , which is caused by min. Surface area due to surface tension ? Could you correct or explain better to me please?
@@MichelvanBiezen excess pressure in curved surface having 2 radii of curvature ............ siR could you make a video on this topic . actuaaly i found no vieooos regarding this topic on utube ....
We have plans to work on that in the future, but that will be some time from now as we are covering a lot of other topics to complete uncompleted playlists.
Hi sir, at 4:10 I want to know why you just used πR² to solve but in reality, we were solving the pressure of 2 halves in a waterdrop, I guess that it is twice as much as the solution.
That is the effective area. Since the forces on the "dome" shape are in all directions, we only need to consider the vertical components of the forces.
When you split the sphere into two hemispheres, why are only water molecules along the circumference attracted to the water molecules above? Instead of all the water molecules along that cross sectional area? A reply would be greatly appreciated!
@@NiranjanKumarGHC Is the internal pressure inside droplet because water/fluid can't compress itself anymore (becoming spherical as min. Surface area is achieved) ?
+Michel van Biezen YES that's what i asked earlier in one of your other videos. why does the soap film has 2 layers and the water has only one surface? and also at the very first video we also multiplied by two to get our Length.
+Abdelrahman Wael Helaly a soap bubble is filled with air inside. There is air outside too. So, it has 2 layers. But, in the case of a water drop, it is it is technically 'consistent', being made up of water only and having no free space inside it to accommodate air. So, it has just a single surface.
+Shrey Wadhwa Rather than integrating over the curved surface to find the total force it is easier to take the average pressure and multiply it by the cross-sectional area.
Interesting would be to point out that small enough droplet would have surface-tension-induced-pressure higher than atmospheric pressure. Is that why droplets cant form by accumulation of water molecules alone and need a condensation nuclei? Edit: no, surface tension pushes inwards of course.
Question sir. How could you describe the behavior of molecules of water at the surface when experiencing unbalance force (intermolecular force) directed towards the bulk of the water due to the absence of water molecules above the surface? Can these molecules at surface obtain equilibrium?
It depends on what you mean by "equilibrium". Even if the molecules do not move position, relative to one another, they will still vibrate due to thermal action and quantum mechanic effects.
great video - I am thinking in context of dust suppression - would smaller drops be less inclined to adhere to say a coal dust particle due to higher internal pressure or am i off track here. regards Jon
We can't jump to such conclusions. That takes a bit of analysis. Adhesion like that has more to do with the electrostatic forces which become more predominant with smaller particles.
@@MichelvanBiezen is it reasonable to say that a surfactant by reducing water tension allows for easier adhesion by altering electrostatic forces between the water and dust particle. apologies for the questions. your lecture had my head ticking over Michel.
Great video but when you converted dyne/cm^2 into Pa you forgotted to divide by factor of 10 in your calculator so all later conversions in atm shoud be 10 times smaller. If you cool water droplets under 0°C would it still be liquid (not supercooled) because of increase of pressure or would ice crystals form on surface => no more tension => ice
a capillary tube having an inside diameter of 6 mm is dipping in oil at 20 degrees Celsius. determine the surface tension of the oil if it raises to a height of 3.4 mm in the Tube Please how can I solve this problem. Please help
Set the weight of the oil raised up 3.4 mm equal to the force caused by the surface tension. Density x volume x g = 2 pi R x coefficient of surface tension Density x pi (6 mm)^2 x 3.4 mm x 9.8 m/sec^2 = 2 pi (6 mm) x coefficient of surface tension x cos (contact angle). We have examples of that in the playlist.
This video is amazing! Thank you for uploading it. I do have a question though. As +Joshua Lin mentioned as r approaches 0 the internal pressure increases and at approximately 0.144mm the pressure inside the droplet reaches 1ATM. What happens to the water droplet at this point?
That is a good observation. Which means that water drops have a lower limit in size and why water drops tend to be of similar size as the force balance appears to make them a typical size.
Hello Michel, I want you to explain me why you took the equivalent area to be the area of cross section. The way I can think about it is that the radially outward vectors keeping the bubble in place are responsible for the bubble to have a dome. Like if the vertical components weren’t there it would’ve been a flat circle. Is it right?
As the drop size gets smaller and smaller a point will be reached when the pressure inside the drop equals the atmospheric pressure. Is this when evaporation start to take place?
sir why is there excess pressure inside a air bubble in water , i seem to mixing up directions and have got confused, could you answer it how or consult a good source material where they have shown the proof explaining surface tension's direction in the question i asked
Think of a balloon. Since the material is stretched there is tension in the material (like surface tension) which causes the air pressure inside the balloon to be greater than the air pressure outside the balloon.
energy of 1 drop (due to surface tension) = coefficient of surface tension x area of 1 drop = 3.657 x 10^-6 J (x 2 for 2 drops). Volume of 2 drops: 6.702 x 10^-8 m^3 Radius of new drop: 2.52 mm energy of new drop = 5.804 x 10^-6J then using Q = mc (delta T) or delta T = Q / mc = (1.509 x 10^-6 J)/mc = 5.38 x 10^-6 K (it seems very small, but that is probably correct)
That is a good question. The way you can tell the difference is as follows: Since total pressure includes atmospheric pressure which is equal to 101,300 Pa, the number should be bigger than that in order to be total pressure. If it is far less, like the 15 Pa in the video, it must be gauge pressure.
+CHALFIER It does, but often there is little difference between different materials and we tend to ignore that unless we are interested in very accurate results.
I know this is very late but it's because Surface tension acts on one layer only, whereas if you are considering a bubble you should multiply by 2 because it has two, outer and inner layer
It is the effective area (not the surface area of the sphere). Note that any vector component of the force perpendicular to the surface has a component that is horizontal and a component that is vertical. Only the vertical component contributes to the force pushing down. That has the effect of converting the total area 4*pi*R^2 to the effective area pi*R^2.
Water molecules are polar molecules, which means that one side is negatively charged and the other side is positively charges, which makes them "stick" together due to electrical forces. (Coulomb forces)
Great video sir! Helped me a lot!
SmarterEveryDay helped? for your next video?
+SmarterEveryDay When you say this, it has to be good :D:D:D
this has to have contributed to that one video of water droplets bouncing on a body of water bc of surface tension
I did not expect to find you here, after 6 years
greetings sir.
your amazing videos and your teaching skills are really impressive and gladly i understand all of your explanations..you've helped me a lot!!
god bless you..
(from mechanical student)
lowformat1
you are correct the final answer is off by a factor of 10
It should be 0.0001437 ATM
Good catch
Hey prof, funny thing! Year ago I watched your video because I was redirected from another channel that credit you. Today I'm here because I'm in a quest for good subject for my assignment from programming class I'm taking (need to compare results from theory and numerical analysis/primitive simulation about some effect). I see you have put annotation with correction and I could't help myself to not notice that it shows "x Pa = y Pa" instead of "x Pa = y atm". I know that I'm nitpicking but I find it bizarrely funny how I'm spotting these.
Hi. I have been struggling about why not taking the whole area of the split sphere. Now I understand is due to the vertical component of the force and equivalent area. It makes total sense! Great video, thank u!! 👍
4:05 , the pressure inside droplet is because of fluids resistance against compression , which is caused by min. Surface area due to surface tension ?
Could you correct or explain better to me please?
Excellent lecture, Survismeter measures surface tension, interfacial tension, viscosity, wettability, coagulability, friccohesity, together.
the same expalnation my teacher gave but i am unable to understand 4:35 why we took area be pie r2 . instead it should by 2pie r2 ....
i got it............ after watching it thrice . thannks teacher ....
Great!
@@MichelvanBiezen excess pressure in curved surface having 2 radii of curvature ............ siR could you make a video on this topic . actuaaly i found no vieooos regarding this topic on utube ....
We have plans to work on that in the future, but that will be some time from now as we are covering a lot of other topics to complete uncompleted playlists.
Hi sir, at 4:10 I want to know why you just used πR² to solve but in reality, we were solving the pressure of 2 halves in a waterdrop, I guess that it is twice as much as the solution.
That is the effective area. Since the forces on the "dome" shape are in all directions, we only need to consider the vertical components of the forces.
When you split the sphere into two hemispheres, why are only water molecules along the circumference attracted to the water molecules above? Instead of all the water molecules along that cross sectional area? A reply would be greatly appreciated!
Because the surface tension acts only on the surface, ie the outer most molecules
@@NiranjanKumarGHC Is the internal pressure inside droplet because water/fluid can't compress itself anymore (becoming spherical as min. Surface area is achieved) ?
I wasn't paying attention to the lecture, thank you for uploading this.
Ibrahim
A water drop has just one surface.
A soap bubble has an inside and an outside surface.
+Michel van Biezen YES that's what i asked earlier in one of your other videos.
why does the soap film has 2 layers and the water has only one surface?
and also at the very first video we also multiplied by two to get our Length.
+Abdelrahman Wael Helaly a soap bubble is filled with air inside. There is air outside too. So, it has 2 layers. But, in the case of a water drop, it is it is technically 'consistent', being made up of water only and having no free space inside it to accommodate air. So, it has just a single surface.
Why did you take πr² instead of area of sphere? I couldn't understand the concept what you told in video.
+Shrey Wadhwa
Rather than integrating over the curved surface to find the total force it is easier to take the average pressure and multiply it by the cross-sectional area.
Interesting would be to point out that small enough droplet would have surface-tension-induced-pressure higher than atmospheric pressure. Is that why droplets cant form by accumulation of water molecules alone and need a condensation nuclei?
Edit: no, surface tension pushes inwards of course.
sorry i would like to ask how to calculate the ellipse
drop's surface tension
i am having trouble understanding how you could just split the droplet into 2 halves....and yet hold the result true for a complete spherical droplet
I think it should be 4gamma/R
Yeah,I think que forgot to contemplate that the force associated with the pressure inside the bubble is the force due to superficial tensión times 2
wow! now this just explains everything. Thank you very much!
thanks by iit jee aspirant
Question sir. How could you describe the behavior of molecules of water at the surface when experiencing unbalance force (intermolecular force) directed towards the bulk of the water due to the absence of water molecules above the surface? Can these molecules at surface obtain equilibrium?
It depends on what you mean by "equilibrium". Even if the molecules do not move position, relative to one another, they will still vibrate due to thermal action and quantum mechanic effects.
Ok sir. Thank you!!
great video - I am thinking in context of dust suppression - would smaller drops be less inclined to adhere to say a coal dust particle due to higher internal pressure or am i off track here. regards Jon
We can't jump to such conclusions. That takes a bit of analysis. Adhesion like that has more to do with the electrostatic forces which become more predominant with smaller particles.
@@MichelvanBiezen is it reasonable to say that a surfactant by reducing water tension allows for easier adhesion by altering electrostatic forces between the water and dust particle. apologies for the questions. your lecture had my head ticking over Michel.
thanks for all the videos (I explicitly search for your name if I have to understand something in physics now)
Happy to help!
sir in this vedio u said that vertical components has the effect but u r taking cross sectional area πR². why not adfing area of hemisphere ?
You can do it that way, but it would be a lot more difficult and you would get the same answer.
thanq sir
Great lecture , thanks from Egypt
Welcome to the channel!
Great video but when you converted dyne/cm^2 into Pa you forgotted to divide by factor of 10 in your calculator so all later conversions in atm shoud be 10 times smaller. If you cool water droplets under 0°C would it still be liquid (not supercooled) because of increase of pressure or would ice crystals form on surface => no more tension => ice
a capillary tube having an inside diameter of 6 mm is dipping in oil at 20 degrees Celsius. determine the surface tension of the oil if it raises to a height of 3.4 mm in the Tube
Please how can I solve this problem. Please help
Set the weight of the oil raised up 3.4 mm equal to the force caused by the surface tension. Density x volume x g = 2 pi R x coefficient of surface tension Density x pi (6 mm)^2 x 3.4 mm x 9.8 m/sec^2 = 2 pi (6 mm) x coefficient of surface tension x cos (contact angle). We have examples of that in the playlist.
This video is amazing! Thank you for uploading it. I do have a question though. As +Joshua Lin mentioned as r approaches 0 the internal pressure increases and at approximately 0.144mm the pressure inside the droplet reaches 1ATM. What happens to the water droplet at this point?
That is a good observation. Which means that water drops have a lower limit in size and why water drops tend to be of similar size as the force balance appears to make them a typical size.
Hello Michel, I want you to explain me why you took the equivalent area to be the area of cross section. The way I can think about it is that the radially outward vectors keeping the bubble in place are responsible for the bubble to have a dome. Like if the vertical components weren’t there it would’ve been a flat circle. Is it right?
That is a way of looking at it, yes.
i am confuse with bubble and drope tension force
amazing video sir
Thanks a lot
thanks for easy explanation!
As the drop size gets smaller and smaller a point will be reached when the pressure inside the drop equals the atmospheric pressure. Is this when evaporation start to take place?
Evaporation will happen at any size
sir why is there excess pressure inside a air bubble in water , i seem to mixing up directions and have got confused, could you answer it how or consult a good source material where they have shown the proof explaining surface tension's direction in the question i asked
Think of a balloon. Since the material is stretched there is tension in the material (like surface tension) which causes the air pressure inside the balloon to be greater than the air pressure outside the balloon.
can you make video on Civil engineering Statics concepts?
We have over a dozen playlists on mechanical engineering.
When two identical droplet fused into each other.How to find deltaT,Sir? Assume that after fusing,big drop is heated.
R=2mm
energy of 1 drop (due to surface tension) = coefficient of surface tension x area of 1 drop = 3.657 x 10^-6 J (x 2 for 2 drops). Volume of 2 drops: 6.702 x 10^-8 m^3 Radius of new drop: 2.52 mm energy of new drop = 5.804 x 10^-6J then using Q = mc (delta T) or delta T = Q / mc = (1.509 x 10^-6 J)/mc = 5.38 x 10^-6 K (it seems very small, but that is probably correct)
Can we not slice the water drop into half and calculate in other ways??
Give it a try and see if you get the same answer.......
so sir , by equating the surface tension force and pressure force in this droplet, the pressure which we found is gauge or absolute??
That is a good question. The way you can tell the difference is as follows: Since total pressure includes atmospheric pressure which is equal to 101,300 Pa, the number should be bigger than that in order to be total pressure. If it is far less, like the 15 Pa in the video, it must be gauge pressure.
How to find surface tension of water jet
Thank you
Does surface tension depend on surrounding material? I think it is, or am I wrong?
+CHALFIER It does, but often there is little difference between different materials and we tend to ignore that unless we are interested in very accurate results.
+Michel van Biezen Thanks for answer.
if p is the pressure then its vertical component cant be also p it should be psin ( theta ) ?
Pressure is not a vector quantity as it acts in all directions from any point.
thanks
bcz its acting from inner portion of the bubble , so i confused it with stress
thanks
why didn't we multiply L by 2, just like we did with the soap bubble ??
I know this is very late but it's because Surface tension acts on one layer only, whereas if you are considering a bubble you should multiply by 2 because it has two, outer and inner layer
How we can calculate coefficient of surface tention
It is not calculated but determined experimentally.
Sir why surface tension is perpendicular to hemispherical surface
The surface tension is tangent to the surface. So if you "cut" the bubble anywhere, the surface tension will be perpendicular to the "cut".
Michel van Biezen sir thank you
you are awesome
best video
sir, why did u take area as pie r square that is supposed to be 4 pie r square right?
It is the effective area (not the surface area of the sphere). Note that any vector component of the force perpendicular to the surface has a component that is horizontal and a component that is vertical. Only the vertical component contributes to the force pushing down. That has the effect of converting the total area 4*pi*R^2 to the effective area pi*R^2.
got it thanks
If the molecules of water is attracted inwards whouldnt it collapse on itself instead of making a spherical shape. Mucho gracis to you :D
It cannot collapse because there are water molecules inside the "surface" caused by the surface tension.
Why does it feel pressure the molecule on the surface of the drop?
The surface tension pulls them together.
@@MichelvanBiezen how? Is it the nuclear force? Magnetism? Gravity? Surface tension is the result, but what causes it?
Water molecules are polar molecules, which means that one side is negatively charged and the other side is positively charges, which makes them "stick" together due to electrical forces. (Coulomb forces)
@@MichelvanBiezen thanks
Thank you soooooooooooooooo much :)
Which country are you from?
Originally I am from Belgium, but now live in the United States.
@@MichelvanBiezen great 💕
❤❤❤❤
Thank you
0:35
That's a false explanation btw.