For me this was quite intuitive. Took some thinking though. Interesting. I tested this with a glass of water on a kitchen scale too, to be sure I got it right :-)
I just got blocked by Quora moderation yesterday, because I edited "anonymous troll" in front of the dumb questions. Now I think Quora moderation is the most stupid thing I have ever seen, how can they allow so many dumb questions in Quora? Seriously, I don't think a person who asked "How do I eat food by my ear" is genuinely seeking an answer, he is just trolling. And this kind of question is basically everywhere on Quora! Now I understand why Lewin left Quora, because Quora is not a knowledge sharing platform, but an entertainment platform.
Friends for sure! So if one is looking at both examples at the same time could one conclude the 1kg difference in both examples is because WL's force pushing the object into the container on the first scale? If so would it be reasonable to say the the force excreted by WL would equal 1kg? If WL let go would the scale show 4kg? Thank you so much for taking the time to teach us folks who did not have or take the opportunity to learn physics in school.
This is a cool puzzle because I think most people would fail to consider the fact that, by Newton's Third Law, due to the fact that water exerts buoyancy on object, object exerts an equal and opposite reaction force on the water, thus compensating for the loss of the weight because some water was spilled out.
Actually, if you think of the container with the water and the ball as a whole system, you can absolutely forget about the tensions and the buoyant forces, as they are all internal. In the end, the weight of the system would obviously consist of the weight of the ball, and the remaining water, so the scale's lecture would be ((M-pV)+m)g. Actually, kinda trivial, a shame that I didn't think of it before
Two long parallel straight wires X and Y separated by a distance 5cm in air carry currents of 10A and 5A resp in opposite directions.Calculate the magnitude and direction of force on a 20cm lenght of the wire Y
thank you sir for the explaination. I am Aagam from India, studying engineering. I have a doubt here. Forget about cases you have taken. Let's say that we have put the ball of volume 'V' in the container filled with water. so due to buoyant force it will float on the surface and displace some amount of water. we don't provide any force and any motion. so the system is in equilibrium. If gravity pulls the object downward, but buoyant force keep forcing the object in upward direction. and hence (rho)*v*g = m*g, then where the other (rho)*v*g comes from? which is in downwards direction. because, it is already seen that action of gravity is reacted by buoyant force with equal magnitude and exactly opposite direction. Please, reply me and provide sufficient guide. and again Thank you for your efforts.
The last problem is simpler then the first! Forget buoyancy; send Archimedes packing. You have a starting mass of M. You add a mass of m, and spill out rho*V. Answer is (M + m - rho*V.)g. First problem is more complicated because buoyant force is "leaving the system" via WL. We are lucky in the first case as the exact same amount of mass is spilled out of the system.
Yes. I did it the way you described. Took me only a few seconds to come up with the right expression for the second case. The first case according to me was a bit tricky too.
Hello sir.. I have questions which is not related to this video...why does velocity of light is change in any medium ...and how that velocity is affect by any medium... what is actual Physics incide it...
Sir but how can it be 5 kg, as the equilibrium condition would be WL+mg=dVg where d is the density of the liquid. WL is the force provided by Walter Lewin. So, I think in both the cases the answer should be 4 kg like the last question. Sir, it is my kind request please mark me if I am wrong!
you are right with the equation so equation suggest we can replace WL and mg(that means ball) with volume of water equal to volume of ball which will be like only water filled completely in container hence weight will be 5 kg
I still love listing to yo doc. Even after you ripped me. I loved this vedio! My question is what if it's only massless forces? Still grateful for your direction!
I believe in experimental evidence in physics. Evidence proof. Did you like my magnetic bottle? I've done a lot more over the last year. Several unusual discoveries in physics and mathematics and geometric forms. I'm not a theoretical physicist. I am a Experimental physicist. We have the coolest toys! I'm studying spin. QM to GR. I love the double slit experiment and John Bells work. And much more. Thank you again for teaching physics!
If I am invited and if all my costs are paid, I will consider it. However, I cannot promise that I will accept the invitation. It's very exhausting. To get over jet lag I will have to be at least 5 days in India before I can give my first lecture. You will also have to pay for these 5 days.
Lectures by Walter Lewin. They will make you ♥ Physics. I see jet lag at this age is very bad to gt over with moreover we dont care about costs bt considering ur age maybe u shouldn't be travelling much :) much more love than making ur life hard ; )
The large mass of Indian full tuition, at MIT all those years you were employed there, when immersed in the vat of water, displaced the lower fees paid by some Americans, leading to the scale reading higher, indicating your salary and pension increased as a result thereof. While in India, an interesting problem for you to lay out and resolve would be to show the effect on Earth's wobble due to mass of Indians with and without large amounts of methane in their gut due to spicy diet.
The container with liquid weighs 5kg - Objects weight is 1kg it displaces 2kg of liquid so 5kg - 2kg "displaced liquid" + "1kg object weight" + 1kg "Walter Lewin down force" = 5kg on bath scale.
Respected Professor, does buoyancy force is influenced by pressure? Example, we have hollow steel ball. If we pump some pressure inside that steel ball, should Buoyancy force increase?
the weight of the ball will increase by the extra air (density 1 atm air is 1.2 kg/m^3). Buoyancy force will stay the same. Net force upwards will therefore decrease.
Thank you for reply. And just one thing. So, if we have car tire, that has aluminium rim, and is pumped with 4 Bar, example, it will not float, but sink just like one without pressure in it? Pressure in that tire has no affect on buoyancy ?
Владислав Остојић: Simple answer (not knowing the volume or density of the rim, tire, etc.)-- If the weight of the tire, rim, and compressed air inside is greater than an equivalent volume of water, it will sink. If that weight is less, it will float. Obviously if you compress the air enough you can get the thing to sink (assuming the tire doesn't explode first). So, pressure in the tire does indeed have an effect on buoyancy. Increased pressure causes increased air density causes decreased buoyancy.
Namaste Professor, I got the second answer correct but while solving first one I considered loss in weight of the body in liquid taking which into account it would weigh [m-(V×rho)]g, while the weight of liquid and container would be shown as [M-(V×rho)]g, as you said Adding these we get [(M+m)-2(V×rho)]g as the weight.. Please show me where did I go wrong.(And thus I got 6kg as the first answer)
The weight loss due to spillage of water is only v*rho*g. As demonstrated by the professor the effect of weight of the ball is due to the reaction force it exerts on to the liquid. So it does not have a part in the weight loss due to spillage. Basically the situation is like Scale reading= (initial weight) - (weight loss due to spillage of water) + (weight gained due the reaction force from the ball)
زين العابدين ماجد sphere exerts force on the water and now consider forces on water 1.reaction force by scale(wieght of the whole system (or setup)) 2. Its own weight 3. The force you are talking about
Professor Walter Lewin I want to know an answer of a question that is ,what is the colour of an electron? sir please answer that question I have asked my teacher he scolded me so if you give me the answer I will be very thankful to you at last live a happy life professor and goodbye. Sir I am from India.
Lectures by Walter Lewin. They will make you ♥ Physics. Sir you are the first teacher who answered my question in very simple way I just loved this answer and simply understand that so for that I really thank you may God bless you and you need for a long period of time may god bless you be happy always good bye sir.
I will send you a signed copy of my book for $25 + postage. Postage is $10 in the US, $30 to Europe and $45 to India. I will write a special note for you in the book. I will also include a signed colored picture of me swinging on the pendulum (with your name written on it). When you transfer the money to my PayPal account let me know your full name and your address (make sure it is correct and complete). *Also let me know very clearly which name I should use for a note in the book and on my picture.* PayPal: lewin-physics@physics.comcastbiz.net
Lectures by Walter Lewin. They will make you ♥ Physics. Thank you sir for your reply sorry I can't believe that a former MIT professor is replying the answer of my question I am truly appreciate it sir thank you for your answer and you live a truly happy life. There are very less teachers like you that answer this type of questions that is truly the product of curiosity. thank you sir for your support thank you. you will live a great and happy life
Lectures by Walter Lewin. They will make you ♥ Physics. Sir I have one more question I want to know that according to you what is the purpose of life? Thank you sir
Sir I want to give you a introduction of mine I am a Highschool student from Basti city of Uttar Pradesh, India I am fascinated by science sir I want to do some different thing that is to help the whole world with new innovations doing different things exploring our world sir I want to do these things so that is what I like and that is what I do so that is my introduction sir I am 15 and half year old sir I want to say you only one thing that you are doing a great work you are a great teacher so sir that is my introduction.
Lectures by Walter Lewin. They will make you ♥ Physics. Sir in mit ocw after watching a video a set of problems is given for us to practice but solution are not given for that problems. in many lectures. Due to this I am facing many difficulty in many questions
