Why am I watching this? Actually I'm a lecturer in medical school and I had a lecture on blood flow in blood vessels which is based on fluid physics and Bernoulli's rule I couldn't think of anything better to prepare for my lecture than watching your lecture on fluid physics it's a good thing that even doctors are watching your lectures Lot of respect professor From Iraq
Dear Mr. Walter Lewin, your lectures are such a pricess gift to me during this hard time. I had always struggled with course name fluid mechanics because the teachers in my school did not explained and demonstrated as clear as you did. It help me regain my motivation to strive to become an engineer. After all, thanks you a lot!!!!.
Thank you very much Prof. Lewin, I have to take my final oral test in physics for engineering next Monday and after all this years of your lecture being around, you are saving my life as those of many other students ! These should be saved as hsitory of science for years to come !
Not only hydrostatics.... Well it's physics which I seem to feel like.... Hope I could ever meet you.... Wanna study in MIT but you don't teach nowadays... Still your lectures are powerful..
@@lecturesbywalterlewin.they9259 sir, at 20:02 the balloon will rise considering there is an atmosphere, because of helium you mentioned, there is a buoyant force even when there is no gravitational acceleration, because of difference in densities.
THATS HOW PHYSICS IS TAUGHT.....I AM COMPLETELY AMAZED...... EARLIER I FOUND FLUIDS VERY DIFFICULT TO UNDERSTAND BUT NOW I ENJOYED LEARNING IT IN THIS LECTURE......THE PRACTICAL DEMONSTRATION WERE JUST TOO GOOD.....
You are the best teacher ever ! I really love your teaching ! I wanna wish you a long and happy life !! You are someone irreplaceable in my heart ...I wanna meet you so badly and say how much your teachings helped me ! Also I really loved your birthday series 💕 Thank you so much again professor Lewis!
Thanks again sir... For the first time I have felt Fluids... Before this I had been thinking that in fluid part there is nothing but puzzles... Now I feel very comfortable in fluids.... Can't pay you against this but infinite respect will always be for you...
Now i am preparing for my neet exam i have many boubts in fluid mechanics after this class i feel comfortable to solve problems of fluid mechanics thank you professor 😊for wonderful class love from India ❤💓
{39:00 -->} You said that when a hole is made in the vessel, water will flow with the same velocity as in the 'syphon case'. But what if both were done simultaneously ? The approximation that v2~0 would not hold good right ?
professor i am from i india, i love to watch your lectures , you explain practically everything. i am in class 10 but i understand everything. it creates me a passion to get phd in physics .thank you professor
I have an answer to the swimming pool question posed at 11:20, but I also have two additional questions regarding the same. The answer to your question: The water level goes down, because if we assume that the density of the stone is greater than the density of water (a reasonable and intuitive assumption), then the stone will sink to the bottom of the pool and settle down. When that happens, the buoyant force that was originally holding up the stone before it was thrown into the water will now be shared between the upward normal force at the bottom of the pool AND the new buoyant force together. Therefore, the new buoyant force is only a fraction of the original buoyant force. Since lower buoyant force displaces lesser water than higher buoyant force, the water level in the pool goes down. (In the event that this is a bottomless pool, then the stone will keep accelerating downwards under its own weight as there is a net force pulling the stone downwards. This net force can only exist if the new buoyant force is lower than its weight, and hence the new buoyant force is lower than the original buoyant force. Thus, the pool level drops). However, I have two variations on the stone that was thrown out: Q 1. What if, instead of a stone, a fish of the same volume as the stone but of the same density as water is thrown out of the boat and into the pool such that the fish goes below the surface of the water but doesn't sink? Would the water level in the pool go up, stay the same, or drop? My (probably wrong) answer: The water level would stay the same. Since the buoyant force is neither being shared by any normal force at the bottom of the tank (as the fish isn't sinking to the pool floor) and nor is the fish accelerating downwards, there is no change in the total buoyant force, which means there is no change in the displaced water. Hence, the water level stays the same. In fact, when the fish is thrown out of the boat, for the brief moment that it is in the air, the water level drops (as the buoyant force drops), but once the fish is under the surface of the water, the water rises again by the same amount that it had dropped, thus equalizing the level. Q 2. What if, instead of a fish, a wooden block of the same volume as the fish but of lower density than water is thrown into the pool such that it floats? Would the water level in the pool go up, stay the same, or drop? My (definitely) wrong answer: The water level would stay the same. There is no change in the total buoyant force here either, as the wooden block isn't sinking to the floor. But I still feel that my answer to this last question is wrong because my inductive reasoning would have led me to believe that if a higher-density object (stone) lowers the water level in the pool, and an equal-density object (fish) keeps the water level the same, then a lower-density object (wood) would have raised the water level. But that is not what the equilibrium equations tell me. Please correct me if I am wrong in any of the above. And yes, your lectures DO make me ♥ physics :)
In the answer to your waterline of swimming pool question, I think it will go down. When we seperate the stone from the boat, the waterline goes down more than the volume of the stone since the density of the boat is lower than the stone. So when the stone sinks the net effect is a lower waterline.
Abjo Das I’m unsure if this is correct but here’s my reasoning. When he inverts the cup, the empty portion above the juice is essentially a weak vacuum with very low pressure. By contrast, the piece of cardboard still feels the full atmospheric pressure pressing it against the cup. Interestingly, however, even though I haven’t done the maths for this claim - I don’t think this will work if the volume or density of liquid is too high. Essentially, you need a fine balance where Patmosphere > (Pcup + weight/area). Is this correct Dr. Lewin?
When the cup is turned upside down, the water wants to fall out. The air-filled cavity is therefore stretched a bit as the gravity pulls down the water. This reduces the air pressure inside the cup, since increasing volume reduces pressure. Eventually this lower pressure pulls upwards with the same force as the weight of the water pulls downwards. The water is now kept in place and the pressure inside is lower than atmospheric pressure outside.
Um, King Hieron II was called a "virtuous man" by Machiavelli and he had a long and seemingly friendly relationship with Archimedes, and his father (a court astronomer) so he'd hardly "kill" him if he got it wrong. :P Great lecture.
At 38:55, syphen experiment. when we suck the water at other end, we created a differential pressure at top and because of this water is raised to max height of tube. once it crosses the max height, gravitational P.E is converted to K.E which resulted into water fall.
Hello Dr. Lewin, this is what I think about the question about the water level changing when you throw the rock overboard. I am a little confused on what you mean by will the water line remain change. Relative to the boat or relative to the walls of the pool? Initially, the water is at a height y_0. The volume of the fluid V_water is given by x*y_0*z where x is width and z is the thickness. For the boat to float, the F_b must equal the weight of the boat and rock. So F_B_0 = (M+m)g (1) where m is the mass of the rock and M is the mass of the boat. Now analyzing the situation when you throw the rock overboard. The mass of the entire boat-rock system must change because we no longer have m. So, in order to float, F_B =Mg. (2) So applying Archimedes Principle to (1.1) V_fluid_0*p_water = V_(M+m)*p_(M+m) and to (2.2) V_fluid*p_water = V_M*p_M . F_B_0 > F_B because of (1) and (2). Therefore. V_fluid_0*p_water > V_fluid*p_water. p_water = M_water/V_water = M_water/x*y_0*z so we have it that: V_fluid_0*M_water_0/xy_oz > V_fluid*M_water/xyz We know that the density of water must remain constant so as we throw the rock overboard, the mass of the fluid M_water increases. So if M_water > M_water_0 and the densities are equivalent, y_0 > y to keep a constant density so the water level will sink.
+Dr. Science Sc.D please summarize your conclusion yes the water level will go down. You did way more work than was needed. Try this. If the volume of the rock is V when the rock is in the boat, more water is displaced than V (Archimedes). When the rock is at the bottom the water displacement is V. Conclusion ==> the water level goes down when you throw the rock over board. .
+Dr. Science Sc.D In these problem the water level is taken relative to the walls of the pool. If it was to be taken in relation to the boat (and then the question would be if the boat sinks in a little bit or a little less, respectively the water level in relation to the boat would rise or would lower). Coincidently, I think the answer of both of the problems is that the water goes down.
Whenever a body is partially or completely submerged in a fluid,it will experience an up thrust which is equal to weight of the fluid which has been displaced.
Just one word. Wow sir. What an amazing lecture. Wish I could meet you someday soon but it happens as if time doesn't allow,, but I'll change it. 😀. For the love of physics -Ayushman(India🇮🇳)
Good night Professor. Checking the deduction of Bernoulli's eq. at Resnick....it says that work at A2,P2,v2 (considering your drawing at 29:20) is negative because the force is opposite to the displacement. Why is this so? is it because we are working with a confined fluid? so it applies Pascal's law?
I derive Bernouilli's eq in one of my 8.01 lectures. Watch it! I cannot add to the clarity of that lecture. You can ask a question about my lecture, please leave Resnick out.
I guess the reason for the last problem being the following; when he turns the glass upside down a tiny amount of liquid runs through the microscopic gap between the glass and the cardboard with a high speed, causing so much low pressure thus the Mg of the liquid is supported. Please correct if I'm wrong.
I think that to understand the pool level problem, it helps being exaggerated. Consider a super dense object, 1 ton with the size of a coin. Now imagine we drop it in a boat that could carry it. Intuitively, the water level would rise significantly to counter the added weight. Now if we drop it in the water, there will be a massive weight relief in the boat and the buoyant force required to keep it floating will be therefore much less. The object has the size of a coin, so the volume of water displaced by it as it sinks is negligible and so is it's buoyancy. The total buoyant force that the water produces will be way less, and so the pool level will drop. As long as the boulder's density is greater than that of water, the same reasoning could be applied.
EUREKA is from REKA, rekao (sam) which on Serbian means Told (I told). Reka also menas river, flows of something, in this case words. It is similar as rhetoRICS, where Rika means roar (also talking meaning, but more in animal terms).
Sir, to answer that question at 11:36 , the water level should go down with respect to the boat, which means a smaller portion of the boat will now be submerged underwater because it does not need to displace the amount of fluid equivalent to the stone's weight. Is this correct?
@@lecturesbywalterlewin.they9259 Sir , related to this Archimedes Principle , there is a classic problem : What will happen when an ice cube floating in fixed water container melts? All books and every source in internet mentions water level will remain the same. To an approximation it will.But should it not decrease slightly? When the ice is initially floating, the volume of water it displaces will lead to an increase in height of water in the container uniformly , except in the portion where the ice cube is protruding out of the water surface. After all the ice has melted, the volume of water displaced will come back and fill the void created by melted ice thus the height falls, but the new water obtained from melted ice will lead to an increase in water's height uniformly even in the area where the ice cube was protruding initially. As volume of the water is same and exposed area has increased slightly owing to no ice being present now, height should fall slightly though that's infinitesimal. Isn't it?
@@santanuchatterjee654 If you keep the water at 0 Celsius the whole experiment, and neglect evaporation and condensation, it will remain unchanged in density, and the water level will remain the same. The ice displaces a volume of water exactly equal to its weight. When the ice melts to 0C liquid water, it backfills that volume, and exactly as much volume as it was displacing when solid.
47:55 Sir please crt me if I'm wrong! In this case..when there is no cardboard covered upon the glass the pressure at any point on the surface of the juice must be 1 atm. After the cardboard has been kept on it and closed ,still it is 1 atm. When I think about what happens when we flip the glass which is closed with a cardboard the air molecules inside the glass goes up and juice comes down where the pressure of air inside the glass is not 1atm anymore and it would have become very low such that you can neglect the pressure of the air . Now if you look at the cardboard there are two pressures acting on it from both the sides,one is 1atm due to the atmosphere and the other one is, whatever the hpg of the juice is. And the hpg is way more less than 1 atm because it is not 10 metres ,if so, it would have pushed the cardboard and as result the cardboard is pushed towards the glass by 1atm pressure outside ! Correct me if I'm wrong sir!🤓
@@lecturesbywalterlewin.they9259 sir that was because you were just sucking out the air inside the tube and when you do that the atmospheric pressure pushes the fluid up you can do it until you are at 10 meters of height...the reason that you were not able to suck it above 1 metre in the previous demonstration was ... you sucked it at a single breath. you could have done that if you do that by taking a breath in between .otherwise you will not be sucking out all the air inside the tube which would actually resist the water coming up....the main reason behind that is... Your lung capacity..you may not be able to suck it more than 1metre at a time but you can do it more than 1 metre by breathing through your nose in between... correct me if I'm wrong sir
at 12:23, I know the high immersed of the boat after throwing the rock is definitely less than it before. So the waterline will go down comparing to the origin. Is it true?
In this case, the helium balloon is already in motion due to its upward buoyancy force, which is caused by the difference in density between the helium inside the balloon and the air outside. When the container is accelerated forward, the balloon, being part of the container, also experiences the same forward acceleration. Since the air in the container is also accelerated forward, there is no relative motion between the air and the helium balloon. Therefore, the buoyancy force acting on the balloon is not affected, and it will continue to move forward with the container. I think this make the concept INTUITIVE
>>> Why don't we consider the weight of the liquid in the pipe to provide pressure at the opening?>>> *bcoz that is wrong* only the vertical distance matters!
>>> Why as vertical distance increase downward, pressure does not increase?>>> when vert distance increases pressure increases. Watch my Lectures or use google
If you replace it with air itself or a gas heavier than air, it will behave like any other pendulum. It will not float in air, it will sink. It will respond the same way a solid pendulum bob will respond, when a car accelerates.
sir in your earlier fluid mechanics video in which 5 meter hose magic was shown could we have even generated 0 atm with continuous block and inblow method
Prof Lewin: The expression at 2:04 implies that the expression for the upthrust , F1, contains g. Why does it contain g if g acts downwards but F1 acts upwards? I don't understand how the pressure acting on the bottom surface can be due, even in part, to gravity.
the temp. inside a balloon and in the surrounding air play a role on the buoyant force no? Is it caused by the expansion of gas increasing the volume thereby increasing the volume of displaced air or is it the temperature effecting the densities of the outside air and the inside air increasing the differential?
Hello There, Can Anybody Explain To Me This -> at 6:34 , He says Archimedes could calculate the density of the crown using the formula - density-crown/density-water but how? if we know density of water at 4*C to be 1000kg/m3 then how I am going to calculate the denstiy of the crown ? Another Video Explained It To Me Like This - Archimedes Knew density of gold and wanted to compare it with that of crown.. for that he needed to know the mass and volume of the crown. Mass he had known but measuring volume sure was a problem. So He immersed it in water, noted the volume of water risen up. As that would be same volume of the crown and used it to calculate the density of the crown. And Then Compared It To That Of Pure Gold. This makes sense, But In The Above Formula, How Will He Able To Calculate The Density ? I know we could simplify further the above formula as - Density-Crown/Density-Water = (mass-crown/volume)/(mass-water/volume) = mass-crown/mass-water. . But This Doesn't Equate To Anything? Note: I am still in 11th, so please ignore any dumb mistakes I am making.
Hello Dr. Lewin! You've told at 10:10 of this video that necessary floating condition is density of a fluid must be larger that density of an object. But modern ships are made from steel, steel density is a way larger than density of water. Why do they float? I think they float because significant part of their volume is not steel, but air inside rooms of underwater part of a ship. This results to average ship's density be smaller than density of the sea water. Is this right? PS: There are some ships made from concrete! en.wikipedia.org/wiki/Concrete_ship Very counter intuitive for me :-)
sir, at 2:26 mins you said F1-F2 is buoyant force...now consider the same problem but only change is that, the cylinder has lower density than the water and i force that cylinder to the bottom of the vessel containing water. Now, that cylinder is completely immersed in water and bottom area of cylinder is completely touching the bottom of vessel. Now, since there is no water below the cylinder, there will not be upward force F1. so, in that case will cylinder rise up since its density is lower than the water? and if yes then what causes it since there is no F1?
>>>Now, since there is no water below the cylinder, there will not be upward force F1>>> Incorrect. The buoyant force upwards equals the *weight of the displace liquid.* (Archimedes!)
sir i have got a doubt!!.... the moment where you went to take the balloon in order to demonstrate the experiment where helium balloon moves forward....at 26:49 when you were moving forward but the balloon was moving backward why sir?
Think about which direction the vehicle is accelerating. When he speeds it up, the vehicle is accelerating to the right. When he slows it down, the vehicle is accelerating to the left. The air in the container moves opposite the acceleration (relative to the vehicle), and the balloon moves opposite that, because the air displaces it.
Professor in the syphon demonstration, the reason why the water runs against gravity is probably due to two reasons........ 1) you mentioned that area of the tube is much smaller than area of the vessel so this means adhesive force inside the tube will dominate over the weight of the juice. 2) if suppose after juice starts flowing and at some point the flow breaks then at that point there is vaccum while at the end of the tube dipped in juice pressure is 1atm.....so this will also drive the juice upwards.......
If the boat has a flat bottom,or otherwise, and is raised to the level of the water,its weight will remain the same,so, if now the stone is thrown into the water will flow overboard so the level of the water will go down,just as the water in Archimedes bath the water fell to the floor.
@Michael Wang The air pressure above the water is lower than the pressure outside the glass, because once you've turned the glass upside down there are fewer air molecules above the water than are outside, which will generate a lower pressure. So, if the pressure difference of the air between outside and inside the glass is lower than the pressure exerted by the weight of liquid, the piece of plastic (or whatever is it) won't fall down.
At 20:52, when you accelerate the compartment in the upward direction with acceleration 'a'...................then for a person of mass 'm' inside that compartment, they will feel a fictitious force or a pseudo force which is 'ma' in the direction that is opposite to the direction of acceleration of the compartment...............so is the term 'ma' which you are referring to as "PERCIEVED GRAVITY"??
I watched from 20:: to 23:00 I cannot add to the clarity of my lecture. If I accelerate the free falling compartment upwards with a, there will be a "perceived" gravitational acceleration downwards of a.
I think the water will lower slightly. The stone will displace its volume of water when tossed in and therefore sink due to density. At this point I believe that the boat will float higher in the water and displace less. The boat was displacing water equal to the weight of the stone which is more water than the volume of the stone. If the stone was same density as water , the level stays the same.
I've always thought the Archimedes legend was a bit much and probably inflated, mostly because Archimedes was an incredibly brilliant mathematician and engineer. You'd think he'd be reasonable. So I couldn't imagine him reacting that absentmindedly to such a relatively basic discovery. But if u consider that he spent an immense amount of effort trying to work out the areas and volumes of weird shapes, having discovered the volume of only a few (The sphere for example), then it becomes much more believable that he'd become euphoric after finding a general way to measure the volume of ANY object using some previously unknown function of nature. Which in that era suggested there may be some relationship between nature and mathematics.
Dear Prof. Walter Lewin, The Ping ball- Funnel experiment was awesome. In case of inverted position (blowing down), what happens when the velocity is kept on increasing ? Will the ball fall down, stick to the top or stabilizes at level below the initial level ?
In the case of a *circular* orbit of a satellite about Earth, F=ma, F is the gravtiational attracting force, a is the acceleration of the satellite. If F is perpendicular to the motion of the satelite its speed will never change but the force changes the direction so that it stays in circular orbit.
sir I need more ellaboration on why ballon moves opposite to the direction of apple. and one more thing I would like to ask can't we ballon moved opposite to apple due to inertia.? will be waiting for your reply
@@RahulKumar-bx7my The balloon will rise because it acts upon it the buoyancy of the air which is bigger from it's weight on the other hand the buoyancy of the air on the apple is way lower than it's weight
Cranberry min 47:00 -- Forces on the juice: 1atmP*Area + Mg - Normal = 0 ,, so Normal = 1atmP*A + Mg Forces on the cardboard: Normal + mg - 1atmP*Area - liquidAdhesion = 0 (calling Normal to the force of the cranberry over the cardboard and liquidAdhesion to the adhesive forces between glass, juice and cardboard) , so we get that { liquidAdhesion = Mg + mg } to get the equilibrium situation. Is that ok? Thanks professor.
I suppose that the main idea is to cover the cardboard with your hand when tilting the glass to avoid a torque on the cardboard. Once the glass is turned down the force on the cardboard is equally distribuited so you need less adhesive force. I suppose that your hand against the weight of the system makes a compression that increse the adhesive force a little too, but I'm not sure about the duration of that effect and it's importance.
Sir, I have a question regarding the experiment at 48:12. Half of the glass is filled with air and half with cranberry juice. Total pressure on the piece of cardboard is pressure of air(inside glass) plus pressure due to the column of cranberry juice (i.e. 1atm + pressure of cranberry juice column) which is obviously greater then the atmospheric pressure (1atm) outside the glass. So inside pressure is greater than the outside pressure still cardboard is not falling down. How is it possible?
I did this experiment myself. But I filled the glass with water to the brim. When I tilted it upside down the cardboard not fell down. I measure height of glass and calculated pressure on cardboard due to water in it. It was about 1127.3 N/m^2 which is way less then atmospheric pressure. But why it didn't fell when it's half filled? I did not understand.
I have never done it with the glass filled to the brim. In any case the adhesion between water and glass and cardboard play a key role to prevent the water from falling out.
OK!!!! So this is due to intermolecular adhesive forces between glass, water and cardboard. I was thinking some type of pressure difference is responsible for this. Now I will do this experiment with materials other then cardboard and will tell you the results.😀
Does it go down because the stone is more dense than water so while it is in the boat is displaces a volume of water equal to its weight but when it is thrown into the water it simply displaces its own volume.
I do not thin Bernoulli's equation is that Bizarre when you think about it. Pressure is a static energy measure while flow is a kinetic energy measure so it stands to reason that they would have a inverse relationship. No different than Amps and Voltage. Any measure of energy in motion will have a inverse static measurement as well. It only stands to reason at least that has been my observation as a mechanic. Cheers!
Hello sir, Great fan of your's from India, I'm not able to see assignments of this lecture through given link in description. Does this link is expired? 🙏
@22.22 what happens when i suck out all the air inside (vacuumed) that room? because the balloon has some pressure inside, will it explode? just curious. Btw I always enjoy your lectures.
sir, i think that at 48:15, the juice didn't fall out because of the tension of liquid but nothing to do with the barometric pressure. The pressure inside the cup (air in cup) is as same as the pressure outside. Is it correct?
Water line goes down. The rock is added weight which the water must then displace by allowing more of the boat in the water. If the boat and its contents are to be considered a system, then just pretend their density is shared, Having a rock in the boat effectively increases its density (its weight per volume). Due to this the boat will sink to a point where Vwater*Pwater*Gravity = Weight of boat. The boat weighs more with the rock, when the rock is thrown away, the volume of water required to meet this wight is lessened. The boat rises, the water line goes down on the side.
What is going on with the juice at the end of the video? Why it does not fall out? I have no clue what is going on. Could you Professor please explain ?
The mass transfer of granberry juice (41 minutes) poses a question: Potential energy is transferred in kinetic energy. V1 will be lower though, due to friction in the tube. By how much (in %), any estimates?
Why? There is adhesion & friction in the tube. It may be ridiculously low, but the only energy where it could come from is the potential. Which means the kinetic must be ever so slightly smaller than the theory predicts. By how much, I wonder.
{Cranberry Juice} I think the cardboard is held to the glass because, some of the area of the cardboard that is outside the glass is at a low pressure than the area that is in contact with the juice. So, according to Bernoulli's principle the cardboard stays with the glass.
Saying Vikas, Sir if a substance having mass density of water whether uniform or not ,then to what depth would it be in equilibrium as all are rightly eligible ..
Q. 2### 35:00 time Sir at this instant why the P1 and P2 are different even being at the same vertical level,seems to be the consequence of flowing fluid
Watching this great lectures series during corona quarantine to enchance my intellect and educate myself in the meantime more.
me tooo
from India ..
That's a very wise decision. Good luck!
Me too also
nile red is way better
Why am I watching this?
Actually I'm a lecturer in medical school and I had a lecture on blood flow in blood vessels which is based on fluid physics and Bernoulli's rule
I couldn't think of anything better to prepare for my lecture than watching your lecture on fluid physics
it's a good thing that even doctors are watching your lectures
Lot of respect professor
From Iraq
Dear Mr. Walter Lewin, your lectures are such a pricess gift to me during this hard time. I had always struggled with course name fluid mechanics because the teachers in my school did not explained and demonstrated as clear as you did. It help me regain my motivation to strive to become an engineer. After all, thanks you a lot!!!!.
Your service and dedication to teach every hungry mind is truly selfless.
Resonance??
Ok go
Thank you very much Prof. Lewin, I have to take my final oral test in physics for engineering next Monday and after all this years of your lecture being around, you are saving my life as those of many other students ! These should be saved as hsitory of science for years to come !
Just because of you....
Today I can feel hydrostatics practically....
Great thanks to W. Lewin sir...
Love from India 💕💖
Not only hydrostatics....
Well it's physics which I seem to feel like....
Hope I could ever meet you....
Wanna study in MIT but you don't teach nowadays...
Still your lectures are powerful..
Wonderful!
@@lecturesbywalterlewin.they9259 🙏🙏🙏
@@lecturesbywalterlewin.they9259 sir, is there any video of quantum mechanics you may have done
@@lecturesbywalterlewin.they9259 sir, at 20:02 the balloon will rise considering there is an atmosphere, because of helium you mentioned, there is a buoyant force even when there is no gravitational acceleration, because of difference in densities.
THATS HOW PHYSICS IS TAUGHT.....I AM COMPLETELY AMAZED......
EARLIER I FOUND FLUIDS VERY DIFFICULT TO UNDERSTAND BUT NOW I ENJOYED LEARNING IT IN THIS LECTURE......THE PRACTICAL DEMONSTRATION WERE JUST TOO GOOD.....
Glad to hear that
You are the best teacher ever ! I really love your teaching ! I wanna wish you a long and happy life !! You are someone irreplaceable in my heart ...I wanna meet you so badly and say how much your teachings helped me !
Also I really loved your birthday series 💕
Thank you so much again professor Lewis!
Your lectures contain all theory demonstration and application ,looking forward to binge watch all your content
Thanks again sir... For the first time I have felt Fluids... Before this I had been thinking that in fluid part there is nothing but puzzles... Now I feel very comfortable in fluids.... Can't pay you against this but infinite respect will always be for you...
Best physics teacher as well as the best physics RUclips I've ever come across. No one else comes even close
:)
This is the best lecture i have found on Archimedes' principle..just wonderful demonstration.
Now i am preparing for my neet exam i have many boubts in fluid mechanics after this class i feel comfortable to solve problems of fluid mechanics thank you professor 😊for wonderful class love from India ❤💓
Wow.i enjoyed every sec of this lecture.
You are the best.
Dr. Lewin's ability to describe and draw complex principles is amazing.
what a MIND BLOWING lecture
47:28 We can all admire the greatness of the MIT chalks in this shot... no wonder why they sound so satisfying
I am in love with physics just because of you. I left my job to teach physics..❤️
{39:00 -->}
You said that when a hole is made in the vessel, water will flow with the same velocity as in the 'syphon case'. But what if both were done simultaneously ?
The approximation that v2~0 would not hold good right ?
both can be used simultaneously. Each would work as if the other was not there.
This is all nice and stuff but the mind blowing part is 0:49
How can he make the dotted lines so effortless? Pure skill!
Honestly I haven't the faintest idea.
he uses the other, or wrong point, of the now angled piece of chalk with pressure and speed on the board to make it "skip" like a stone on water
professor i am from i india, i love to watch your lectures , you explain practically everything. i am in class 10 but i understand everything. it creates me a passion to get phd in physics .thank you professor
I have an answer to the swimming pool question posed at 11:20, but I also have two additional questions regarding the same.
The answer to your question: The water level goes down, because if we assume that the density of the stone is greater than the density of water (a reasonable and intuitive assumption), then the stone will sink to the bottom of the pool and settle down. When that happens, the buoyant force that was originally holding up the stone before it was thrown into the water will now be shared between the upward normal force at the bottom of the pool AND the new buoyant force together. Therefore, the new buoyant force is only a fraction of the original buoyant force. Since lower buoyant force displaces lesser water than higher buoyant force, the water level in the pool goes down.
(In the event that this is a bottomless pool, then the stone will keep accelerating downwards under its own weight as there is a net force pulling the stone downwards. This net force can only exist if the new buoyant force is lower than its weight, and hence the new buoyant force is lower than the original buoyant force. Thus, the pool level drops).
However, I have two variations on the stone that was thrown out:
Q 1. What if, instead of a stone, a fish of the same volume as the stone but of the same density as water is thrown out of the boat and into the pool such that the fish goes below the surface of the water but doesn't sink? Would the water level in the pool go up, stay the same, or drop?
My (probably wrong) answer: The water level would stay the same. Since the buoyant force is neither being shared by any normal force at the bottom of the tank (as the fish isn't sinking to the pool floor) and nor is the fish accelerating downwards, there is no change in the total buoyant force, which means there is no change in the displaced water. Hence, the water level stays the same.
In fact, when the fish is thrown out of the boat, for the brief moment that it is in the air, the water level drops (as the buoyant force drops), but once the fish is under the surface of the water, the water rises again by the same amount that it had dropped, thus equalizing the level.
Q 2. What if, instead of a fish, a wooden block of the same volume as the fish but of lower density than water is thrown into the pool such that it floats? Would the water level in the pool go up, stay the same, or drop?
My (definitely) wrong answer: The water level would stay the same. There is no change in the total buoyant force here either, as the wooden block isn't sinking to the floor.
But I still feel that my answer to this last question is wrong because my inductive reasoning would have led me to believe that if a higher-density object (stone) lowers the water level in the pool, and an equal-density object (fish) keeps the water level the same, then a lower-density object (wood) would have raised the water level. But that is not what the equilibrium equations tell me.
Please correct me if I am wrong in any of the above.
And yes, your lectures DO make me ♥ physics :)
Watch my lectures - Your answers are there!
In the answer to your waterline of swimming pool question, I think it will go down. When we seperate the stone from the boat, the waterline goes down more than the volume of the stone since the density of the boat is lower than the stone. So when the stone sinks the net effect is a lower waterline.
The water level stays the same
He (Walter Levin) said it would change! Need I say he is right?
44:55 "That's the reason she couldn't get it up. That's what Bernoulli does to you" - Lewis
another CLASSIC Lecture by Dr Walter Lewin :D .. great Demonstrations, Excellent Chalk Board Graphics.... Thank you.
:)
I wish I could actually sit there and learn these lectures from you
How did the cranberry juice not fall when it was tilted over in 48:00 min?
Abjo Das I’m unsure if this is correct but here’s my reasoning. When he inverts the cup, the empty portion above the juice is essentially a weak vacuum with very low pressure. By contrast, the piece of cardboard still feels the full atmospheric pressure pressing it against the cup. Interestingly, however, even though I haven’t done the maths for this claim - I don’t think this will work if the volume or density of liquid is too high. Essentially, you need a fine balance where Patmosphere > (Pcup + weight/area). Is this correct Dr. Lewin?
When the cup is turned upside down, the water wants to fall out. The air-filled cavity is therefore stretched a bit as the gravity pulls down the water. This reduces the air pressure inside the cup, since increasing volume reduces pressure.
Eventually this lower pressure pulls upwards with the same force as the weight of the water pulls downwards. The water is now kept in place and the pressure inside is lower than atmospheric pressure outside.
We usually did it with the glass which was full [of water].
Surprising that it works also with a glass which is 25% empty.
Um, King Hieron II was called a "virtuous man" by Machiavelli and he had a long and seemingly friendly relationship with Archimedes, and his father (a court astronomer) so he'd hardly "kill" him if he got it wrong. :P Great lecture.
do you have any video on surface tension , capillarity and all that stuff
I may have covered some of it in 8.01. I do not remember.
Amazing lecture. And the rod he used in the water to explain stable and unstable equilibrium has colours of Indian flag. :)
This lecture is awesome. Thank you ❤️
:)
Thank you so much for these meneer Lewin, ze zijn erg behulpzaam aan mijn understanding van physics
After watching your lectures
I sometimes doubt my intelligence it seems like what the hell i have studied from past 2 years😂😂
YES! I studied these exact same concepts, only to better understand them here.
At 38:55, syphen experiment.
when we suck the water at other end, we created a differential pressure at top and because of this water is raised to max height of tube. once it crosses the max height, gravitational P.E is converted to K.E which resulted into water fall.
Woww
Hello Dr. Lewin, this is what I think about the question about the water level changing when you throw the rock overboard.
I am a little confused on what you mean by will the water line remain change. Relative to the boat or relative to the walls of the pool?
Initially, the water is at a height y_0. The volume of the fluid V_water is given by x*y_0*z where x is width and z is the thickness. For the boat to float, the F_b must equal the weight of the boat and rock. So F_B_0 = (M+m)g (1) where m is the mass of the rock and M is the mass of the boat.
Now analyzing the situation when you throw the rock overboard. The mass of the entire boat-rock system must change because we no longer have m. So, in order to float, F_B =Mg. (2)
So applying Archimedes Principle to (1.1) V_fluid_0*p_water = V_(M+m)*p_(M+m) and to (2.2) V_fluid*p_water = V_M*p_M . F_B_0 > F_B because of (1) and (2).
Therefore. V_fluid_0*p_water > V_fluid*p_water.
p_water = M_water/V_water = M_water/x*y_0*z so we have it that:
V_fluid_0*M_water_0/xy_oz > V_fluid*M_water/xyz
We know that the density of water must remain constant so as we throw the rock overboard, the mass of the fluid M_water increases. So if M_water > M_water_0 and the densities are equivalent, y_0 > y to keep a constant density so the water level will sink.
+Dr. Science Sc.D please summarize your conclusion yes the water level will go down. You did way more work than was needed. Try this. If the volume of the rock is V when the rock is in the boat, more water is displaced than V (Archimedes). When the rock is at the bottom the water displacement is V. Conclusion ==> the water level goes down when you throw the rock over board. .
+Dr. Science Sc.D In these problem the water level is taken relative to the walls of the pool. If it was to be taken in relation to the boat (and then the question would be if the boat sinks in a little bit or a little less, respectively the water level in relation to the boat would rise or would lower). Coincidently, I think the answer of both of the problems is that the water goes down.
Thank you so much professor,...
Very easy to understand with your demonstration...
Whenever a body is partially or completely submerged in a fluid,it will experience an up thrust which is equal to weight of the fluid which has been displaced.
At, 35:08 P1
Just one word. Wow sir.
What an amazing lecture. Wish I could meet you someday soon but it happens as if time doesn't allow,, but I'll change it. 😀. For the love of physics -Ayushman(India🇮🇳)
Good night Professor. Checking the deduction of Bernoulli's eq. at Resnick....it says that work at A2,P2,v2 (considering your drawing at 29:20) is negative because the force is opposite to the displacement. Why is this so? is it because we are working with a confined fluid? so it applies Pascal's law?
I derive Bernouilli's eq in one of my 8.01 lectures. Watch it! I cannot add to the clarity of that lecture. You can ask a question about my lecture, please leave Resnick out.
xD ok. I'll leave Resnick out! Thank you professor.
I guess the reason for the last problem being the following; when he turns the glass upside down a tiny amount of liquid runs through the microscopic gap between the glass and the cardboard with a high speed, causing so much low pressure thus the Mg of the liquid is supported. Please correct if I'm wrong.
I think that to understand the pool level problem, it helps being exaggerated. Consider a super dense object, 1 ton with the size of a coin. Now imagine we drop it in a boat that could carry it. Intuitively, the water level would rise significantly to counter the added weight. Now if we drop it in the water, there will be a massive weight relief in the boat and the buoyant force required to keep it floating will be therefore much less. The object has the size of a coin, so the volume of water displaced by it as it sinks is negligible and so is it's buoyancy. The total buoyant force that the water produces will be way less, and so the pool level will drop. As long as the boulder's density is greater than that of water, the same reasoning could be applied.
Binging bigtime on these lectures rn
5:26 how did he know about gravitational acceleration?
34:54 Does someone have any other explanation for this statement?
EUREKA is from REKA, rekao (sam) which on Serbian means Told (I told). Reka also menas river, flows of something, in this case words.
It is similar as rhetoRICS, where Rika means roar (also talking meaning, but more in animal terms).
Sir, to answer that question at 11:36 , the water level should go down with respect to the boat, which means a smaller portion of the boat will now be submerged underwater because it does not need to displace the amount of fluid equivalent to the stone's weight. Is this correct?
correct
@@lecturesbywalterlewin.they9259 Sir , related to this Archimedes Principle , there is a classic problem : What will happen when an ice cube floating in fixed water container melts?
All books and every source in internet mentions water level will remain the same. To an approximation it will.But should it not decrease slightly? When the ice is initially floating, the volume of water it displaces will lead to an increase in height of water in the container uniformly , except in the portion where the ice cube is protruding out of the water surface. After all the ice has melted, the volume of water displaced will come back and fill the void created by melted ice thus the height falls, but the new water obtained from melted ice will lead to an increase in water's height uniformly even in the area where the ice cube was protruding initially. As volume of the water is same and exposed area has increased slightly owing to no ice being present now, height should fall slightly though that's infinitesimal. Isn't it?
@@santanuchatterjee654 If you keep the water at 0 Celsius the whole experiment, and neglect evaporation and condensation, it will remain unchanged in density, and the water level will remain the same. The ice displaces a volume of water exactly equal to its weight. When the ice melts to 0C liquid water, it backfills that volume, and exactly as much volume as it was displacing when solid.
47:55 Sir please crt me if I'm wrong! In this case..when there is no cardboard covered upon the glass the pressure at any point on the surface of the juice must be 1 atm. After the cardboard has been kept on it and closed ,still it is 1 atm. When I think about what happens when we flip the glass which is closed with a cardboard the air molecules inside the glass goes up and juice comes down where the pressure of air inside the glass is not 1atm anymore and it would have become very low such that you can neglect the pressure of the air . Now if you look at the cardboard there are two pressures acting on it from both the sides,one is 1atm due to the atmosphere and the other one is, whatever the hpg of the juice is. And the hpg is way more less than 1 atm because it is not 10 metres ,if so, it would have pushed the cardboard and as result the cardboard is pushed towards the glass by 1atm pressure outside ! Correct me if I'm wrong sir!🤓
you have not explained why I was able to suck up liquid over a distance of about 5 meter.
@@lecturesbywalterlewin.they9259 sir that was because you were just sucking out the air inside the tube and when you do that the atmospheric pressure pushes the fluid up you can do it until you are at 10 meters of height...the reason that you were not able to suck it above 1 metre in the previous demonstration was ... you sucked it at a single breath. you could have done that if you do that by taking a breath in between .otherwise you will not be sucking out all the air inside the tube which would actually resist the water coming up....the main reason behind that is... Your lung capacity..you may not be able to suck it more than 1metre at a time but you can do it more than 1 metre by breathing through your nose in between... correct me if I'm wrong sir
@@lecturesbywalterlewin.they9259 sir please reply sir😅🤓
at 12:23, I know the high immersed of the boat after throwing the rock is definitely less than it before. So the waterline will go down comparing to the origin. Is it true?
ok
Can't describe the experience, amazing Thank You🙏🙏
In this case, the helium balloon is already in motion due to its upward buoyancy force, which is caused by the difference in density between the helium inside the balloon and the air outside. When the container is accelerated forward, the balloon, being part of the container, also experiences the same forward acceleration.
Since the air in the container is also accelerated forward, there is no relative motion between the air and the helium balloon. Therefore, the buoyancy force acting on the balloon is not affected, and it will continue to move forward with the container.
I think this make the concept INTUITIVE
sorry but wouldn't it be the inertia that keeps the apple fall backwards or stay in position while the comparment moves
loved the lecture btw
NOOOOOOOOOOO
@@lecturesbywalterlewin.they9259 There is no force to accelerate the apple only the string so inertia must play a role.
I think you are correct!
Why at 36:18, at the opening pressure is 1atm? Why don't we consider the weight of the liquid in the pipe to provide pressure at the opening?
>>> Why don't we consider the weight of the liquid in the pipe to provide pressure at the opening?>>>
*bcoz that is wrong* only the vertical distance matters!
Lectures by Walter Lewin. They will make you ♥ Physics. Why as vertical distance increase downward, pressure does not increase in 36:18?
>>> Why as vertical distance increase downward, pressure does not increase?>>> when vert distance increases pressure increases. Watch my Lectures or use google
Lectures by Walter Lewin. They will make you ♥ Physics. I edited my question
when vert distance increases pressure at the bottom increases. Watch my Lectures or use google. This is my last msg on this topic.
I remember this Archimedes problem from your video - Problem #29 (=
Wow! This is very interesting lecture.
Here; the water level goes down because when the rock was in the the boat the displaced water, is greater then when t it through down.
what if the rock is floating on the water?
@@neillin8212 then it stays the same
{22:00 ->}
What would happen if the He inside the balloon is replaced by some other heavier gas (or gas that is heavier than air) ?
any balloon filled with air or a gas heavier than air would not float
If you replace it with air itself or a gas heavier than air, it will behave like any other pendulum. It will not float in air, it will sink. It will respond the same way a solid pendulum bob will respond, when a car accelerates.
sir in your earlier fluid mechanics video in which 5 meter hose magic was shown
could we have even generated 0 atm with continuous block and inblow method
Prof Lewin: The expression at 2:04 implies that the expression for the upthrust , F1, contains g. Why does it contain g if g acts downwards but F1 acts upwards? I don't understand how the pressure acting on the bottom surface can be due, even in part, to gravity.
google: "Pascal's Law" and google "Hydrostatic Pressure"
I will do, thanks.
Should the Navier-Stokes equation be covered for this chapter?
no , i think this video is only for +1 or +2 only , but what are you asking is a undergraduate concept :-) !!!
the temp. inside a balloon and in the surrounding air play a role on the buoyant force no? Is it caused by the expansion of gas increasing the volume thereby increasing the volume of displaced air or is it the temperature effecting the densities of the outside air and the inside air increasing the differential?
Archimedes' Principle
Hello There, Can Anybody Explain To Me This ->
at 6:34 , He says Archimedes could calculate the density of the crown using the formula -
density-crown/density-water
but how? if we know density of water at 4*C to be 1000kg/m3 then how I am going to calculate the denstiy of the crown ?
Another Video Explained It To Me Like This -
Archimedes Knew density of gold and wanted to compare it with that of crown.. for that he needed to know the mass and volume of the crown. Mass he had known but measuring volume sure was a problem. So He immersed it in water, noted the volume of water risen up. As that would be same volume of the crown and used it to calculate the density of the crown. And Then Compared It To That Of Pure Gold.
This makes sense, But In The Above Formula, How Will He Able To Calculate The Density ?
I know we could simplify further the above formula as -
Density-Crown/Density-Water = (mass-crown/volume)/(mass-water/volume) = mass-crown/mass-water.
.
But This Doesn't Equate To Anything? Note: I am still in 11th, so please ignore any dumb mistakes I am making.
use google
Hello Dr. Lewin! You've told at 10:10 of this video that necessary floating condition is density of a fluid must be larger that density of an object. But modern ships are made from steel, steel density is a way larger than density of water. Why do they float? I think they float because significant part of their volume is not steel, but air inside rooms of underwater part of a ship. This results to average ship's density be smaller than density of the sea water. Is this right?
PS: There are some ships made from concrete! en.wikipedia.org/wiki/Concrete_ship
Very counter intuitive for me :-)
I think you are correct. Consider the average density of the whole ship, It is mainly air if we think about it. That's why it floats.
sir, at 2:26 mins you said F1-F2 is buoyant force...now consider the same problem but only change is that, the cylinder has lower density than the water and i force that cylinder to the bottom of the vessel containing water. Now, that cylinder is completely immersed in water and bottom area of cylinder is completely touching the bottom of vessel. Now, since there is no water below the cylinder, there will not be upward force F1. so, in that case will cylinder rise up since its density is lower than the water? and if yes then what causes it since there is no F1?
>>>Now, since there is no water below the cylinder, there will not be upward force F1>>>
Incorrect. The buoyant force upwards equals the *weight of the displace liquid.* (Archimedes!)
sir i have got a doubt!!.... the moment where you went to take the balloon in order to demonstrate the experiment where helium balloon moves forward....at 26:49 when you were moving forward but the balloon was moving backward why sir?
Think about which direction the vehicle is accelerating. When he speeds it up, the vehicle is accelerating to the right. When he slows it down, the vehicle is accelerating to the left. The air in the container moves opposite the acceleration (relative to the vehicle), and the balloon moves opposite that, because the air displaces it.
Professor in the syphon demonstration, the reason why the water runs against gravity is probably due to two reasons........
1) you mentioned that area of the tube is much smaller than area of the vessel so this means adhesive force inside the tube will dominate over the weight of the juice.
2) if suppose after juice starts flowing and at some point the flow breaks then at that point there is vaccum while at the end of the tube dipped in juice pressure is 1atm.....so this will also drive the juice upwards.......
google syphon - it's all there
If the boat has a flat bottom,or otherwise, and is raised to the level of the water,its weight will remain the same,so, if now the stone is thrown into the water will flow overboard so the level of the water will go down,just as the water in Archimedes bath the water fell to the floor.
Hello why a fly inside a car doesnt go to the back when the car is moving?
THINKKKKKKK think about a fly in an airplane
Because the air inside the plane goes with him? So the fly has the same behavior?
at 35:00 do you mean fluid travels from lower pressure to higher pressure?????????
I watched from 34:00 to 36:00
I cannot improve on what I said,
"they will get some of their 25000 dollars intuition back"
sir, can you pleaese explain me your last demonstration theorotically. how that works?
that's up to you to explain
sir, is the answer is decrease in pressure?
@Michael Wang The air pressure above the water is lower than the pressure outside the glass, because once you've turned the glass upside down there are fewer air molecules above the water than are outside, which will generate a lower pressure. So, if the pressure difference of the air between outside and inside the glass is lower than the pressure exerted by the weight of liquid, the piece of plastic (or whatever is it) won't fall down.
At 20:52, when you accelerate the compartment in the upward direction with acceleration 'a'...................then for a person of mass 'm' inside that compartment, they will feel a fictitious force or a pseudo force which is 'ma' in the direction that is opposite to the direction of acceleration of the compartment...............so is the term 'ma' which you are referring to as "PERCIEVED GRAVITY"??
I watched from 20:: to 23:00
I cannot add to the clarity of my lecture.
If I accelerate the free falling compartment upwards with a, there will be a "perceived" gravitational acceleration downwards of a.
I think the water will lower slightly. The stone will displace its volume of water when tossed in and therefore sink due to density. At this point I believe that the boat will float higher in the water and displace less. The boat was displacing water equal to the weight of the stone which is more water than the volume of the stone. If the stone was same density as water , the level stays the same.
I've always thought the Archimedes legend was a bit much and probably inflated, mostly because Archimedes was an incredibly brilliant mathematician and engineer. You'd think he'd be reasonable. So I couldn't imagine him reacting that absentmindedly to such a relatively basic discovery. But if u consider that he spent an immense amount of effort trying to work out the areas and volumes of weird shapes, having discovered the volume of only a few (The sphere for example), then it becomes much more believable that he'd become euphoric after finding a general way to measure the volume of ANY object using some previously unknown function of nature. Which in that era suggested there may be some relationship between nature and mathematics.
Hehe
Not a basic discovery at all.
Dear Prof. Walter Lewin,
The Ping ball- Funnel experiment was awesome. In case of inverted position (blowing down), what happens when the velocity is kept on increasing ? Will the ball fall down, stick to the top or stabilizes at level below the initial level ?
It will probably depend on the kind of funnel that is used but given enough air pressure (from above) it will probably fall out.
Thank you.
bernaolli eq at 29:00
Under what conditions as space accelerated with the apple, the apple would go in the direction in which it is accelerating?
In the case of a *circular* orbit of a satellite about Earth, F=ma, F is the gravtiational attracting force, a is the acceleration of the satellite. If F is perpendicular to the motion of the satelite its speed will never change but the force changes the direction so that it stays in circular orbit.
Isn't coanda effect better explanation for the stability of the ping pong ball than bernoulli principle???
sir I need more ellaboration on why ballon moves opposite to the direction of apple.
and one more thing I would like to ask can't we ballon moved opposite to apple due to inertia.?
will be waiting for your reply
use google
@@lecturesbywalterlewin.they9259 nothing can beat your explanation sir !!!!!
@@RahulKumar-bx7my The balloon will rise because it acts upon it the buoyancy of the air which is bigger from it's weight on the other hand the buoyancy of the air on the apple is way lower than it's weight
Cranberry min 47:00 --
Forces on the juice: 1atmP*Area + Mg - Normal = 0 ,, so Normal = 1atmP*A + Mg
Forces on the cardboard: Normal + mg - 1atmP*Area - liquidAdhesion = 0 (calling Normal to the force of the cranberry over the cardboard and liquidAdhesion to the adhesive forces between glass, juice and cardboard) , so we get that { liquidAdhesion = Mg + mg } to get the equilibrium situation. Is that ok? Thanks professor.
PLEASE explain How I did it. NO equations needed.
I suppose that the main idea is to cover the cardboard with your hand when tilting the glass to avoid a torque on the cardboard. Once the glass is turned down the force on the cardboard is equally distribuited so you need less adhesive force. I suppose that your hand against the weight of the system makes a compression that increse the adhesive force a little too, but I'm not sure about the duration of that effect and it's importance.
I looked at 47:00 I do not understand what you wrote. I discuss Bernouilli and do a ping pong ball demo.
min 47:30 , the cranberry juice demonstration
explain in with words. No need to use any equations.
Sir, I have a question regarding the experiment at 48:12. Half of the glass is filled with air and half with cranberry juice. Total pressure on the piece of cardboard is pressure of air(inside glass) plus pressure due to the column of cranberry juice (i.e. 1atm + pressure of cranberry juice column) which is obviously greater then the atmospheric pressure (1atm) outside the glass. So inside pressure is greater than the outside pressure still cardboard is not falling down. How is it possible?
it's up to you to find out!
I did this experiment myself. But I filled the glass with water to the brim. When I tilted it upside down the cardboard not fell down. I measure height of glass and calculated pressure on cardboard due to water in it. It was about 1127.3 N/m^2 which is way less then atmospheric pressure. But why it didn't fell when it's half filled? I did not understand.
I have never done it with the glass filled to the brim. In any case the adhesion between water and glass and cardboard play a key role to prevent the water from falling out.
OK!!!! So this is due to intermolecular adhesive forces between glass, water and cardboard. I was thinking some type of pressure difference is responsible for this. Now I will do this experiment with materials other then cardboard and will tell you the results.😀
In your questions about the boat and the rock, does the water drop to level ?! I concluded that, is it correct?
Does it go down because the stone is more dense than water so while it is in the boat is displaces a volume of water equal to its weight but when it is thrown into the water it simply displaces its own volume.
yes
I do not thin Bernoulli's equation is that Bizarre when you think about it. Pressure is a static energy measure while flow is a kinetic energy measure so it stands to reason that they would have a inverse relationship. No different than Amps and Voltage. Any measure of energy in motion will have a inverse static measurement as well. It only stands to reason at least that has been my observation as a mechanic. Cheers!
Hey I can't understand why didn't the berry juice fall can somebody tell me
Hello sir, Great fan of your's from India,
I'm not able to see assignments of this lecture through given link in description. Does this link is expired? 🙏
PDF's have not expired. Most viewers do not now how ot use them. I suggest you use playlist "8.01 Homework, Solutions, Exams & Notes"
Ok sir great👍 and thank you!!
@22.22 what happens when i suck out all the air inside (vacuumed) that room? because the balloon has some pressure inside, will it explode? just curious. Btw I always enjoy your lectures.
Most definitely, for any real balloon.
I love each one of your lecture, each one. Thank you so much!
so sir, do u mean that the ship's centre of mass should be as low as possible to attain maximum stability?
yes
That's why the ships have intentional extra mass at the bottom of their hulls.
7:00
"Consider a spherical cow"
sir, i think that at 48:15, the juice didn't fall out because of the tension of liquid but nothing to do with the barometric pressure. The pressure inside the cup (air in cup) is as same as the pressure outside. Is it correct?
Now the question is, why pressure inside the cup is less than outside?
At 24:52 can we say that the pendulum moves to the left because of conservation of momentum ?
watch my lecture I explain it.
Water line goes down. The rock is added weight which the water must then displace by allowing more of the boat in the water. If the boat and its contents are to be considered a system, then just pretend their density is shared, Having a rock in the boat effectively increases its density (its weight per volume). Due to this the boat will sink to a point where Vwater*Pwater*Gravity = Weight of boat. The boat weighs more with the rock, when the rock is thrown away, the volume of water required to meet this wight is lessened. The boat rises, the water line goes down on the side.
What is going on with the juice at the end of the video? Why it does not fall out? I have no clue what is going on. Could you Professor please explain ?
I do not explain this. You have to figure it out
The mass transfer of granberry juice (41 minutes) poses a question: Potential energy is transferred in kinetic energy. V1 will be lower though, due to friction in the tube. By how much (in %), any estimates?
you are off on a wrong track.
Why? There is adhesion & friction in the tube. It may be ridiculously low, but the only energy where it could come from is the potential. Which means the kinetic must be ever so slightly smaller than the theory predicts. By how much, I wonder.
you are off on the wrong track.
My name is Emmanuel from Nigeria
I love the way you teach.
Please I want you to be my tutor in physics so that I can impact knowledge in my students
{Cranberry Juice}
I think the cardboard is held to the glass because, some of the area of the cardboard that is outside the glass is at a low pressure than the area that is in contact with the juice. So, according to Bernoulli's principle the cardboard stays with the glass.
incorrect
Saying Vikas,
Sir if a substance having mass density of water whether uniform or not ,then to what depth would it be in equilibrium as all are rightly eligible ..
question unclear - watch my 8.01 lectures
Q. 2###
35:00 time
Sir at this instant why the P1 and P2 are different even being at the same vertical level,seems to be the consequence of flowing fluid
I hope you have just the two lecture 27 and 28 on fluid mechanics that may guarantee JEe mains and advance India for fluid mechanics