Professor, after watching your content I have become more confident in exploring and decoding the subtleties of physics in everyday life. Regards from India.
thank you for letting me understand physics! it felt nearly impossible until I was directed to watch your videos by my professor at community college amidst covid-19.
I hope your channel can come to more people in my country A lot of students in my country don’t know how to learn physics correctly. Therefore they can not know the beauty of physics. Last 1 year, i hate physics and don’t know how to learn. But now you light up my light, my best teacher. I hope i can continue your job in order to make physics shine again in my country.
I am feeling like taking up a career in research in physics, instead of engineering now....after watching your wonderful lectures. Thank you Professor...
Dear Professor I really would like to thank you so much, your lectures and your way of teaching impressed me from the first time I saw your lectures a few years ago, and each time I see them again, I feel the same excitement as the first time when I saw them. So I hope to be like you someday.
I'm currently an 11th grader, I find physics an interesting subject and wish to be a physicist but a majority of people from my area view physics only as a subject where they need good score to either become a doctor or an engineer, before watching this lecture, I was learning about classical mechanics from another teacher from my country, and to my shock all he did was show some mcqs on the screen and tell the answer without even explaining how he got them, all he said was"This is a very important question which will be definitely coming in your exams, learn it by heart, note it down or take a screenshot", like dude, are we only studying for the sake of exams? I got really frustrated and then remembered about Walter Lewin's lectures. I'm so glad to have remembered about it and very grateful for these amazing series of lectures.
Hi, I'm in the high school where we don't learn much, so I watch your lectures which they taught me that physics is even more wonderful than I taught. Thanks for sharing them for free! Best regards, not from India, but from Slovenia!
"Thank u sir for making the lecture so good" THERE IS SOME SPECIAL FEELIN YOUR LECTURES THAT MAKES PHYSICS LOOK MORE BEAUTIFUL. 😊😇😊 "You made my day, because i was struggling to understand these topics" LOVE FROM INDIA🇮🇳
How good is this guy!?? His talent, passion and attention to detail is something i will aspire to achieve. Thank you so much for sharing these lectures
Thank you, how can I ever thank you!! My jee exams are coming, and this topic was ghastly for me, as is for most students I believe. And honestly the first lecture series I watched from you. Thank you. I am crying.
It would be a perfect world if teachers did one solid and always supported the theory they present with actual practical examples, just like professor Lewin. This is how you teach physics, you predict, you show, there you go!
Its really gobsmacking that you are so equivocal about the contents and the way you teach ,that exhilaration in you is just amazing sir.Hats off!!!! Love from India! Will really love to meet you some day
38:52 that derivation made my day, i am very satisfied i always use to wonder how people simulated motion of 3D objects , but now i know if i can parameterize the surface of 3D object i can simple calculate a higher integral and find the center of mass and translate that origin of the object with respect to only the force at center of mass of the object :)..very interesting.
*8.01x Lecture 15* ---- 0:05 momentum 4:30 conservation of momentum 6:30 example 1 11:00 about kinetic energy before & after (Real big deal in Physics) 20:00 never confuse momentum vs kinetic energy 23:10 hold m1&m2 by a compressed spring 28:00 air track 36:00 centre of mass 41:20 find centre of mass 46:13 motion of centre of mass 50:00 tennis racket trajectory *see more here:* zyzx.haust.edu.cn/moocresource/data/20080421/U/01220/OcwWeb/Physics/8-01Physics-IFall1999/VideoLectures/detail/Video-Segment-Index-for-L-15.htm ----- *We love the way you make Physics interesting!*
Wow I just found this channel after I search on google best physics professor bcz my favourite subject is physics and it's really best lectures and best teaching way ❤️. Thanks walter lewin for this. Now I'm gonna watch whole videos. So much respect from india🙏.
Watch all my 94 MIT course lectures. Start with 8.01, then 8.02, then 8.03. Do all the homework and take all my exams. *I guarantee you that you will then do very well on the Physics portion of any freshman college or JEE exam*
I always had something special feeling for physics, and Professor Walter Lewin sir, you have amplified it entirely, now I love physics and wanna persuit a career in it... Sir but I have been confused of its job market, please sir give me some advise❤
@@lecturesbywalterlewin.they9259 please sir I need a Professional like you to give me an honest advise😢 Shall I not go for it even I love it? Btw, thanks for your reply... Love from Bangladesh ❤❤
Dear Walter, Thank you for these video lectures. I don't understand the math ( mostly at all ) but I feel I'm learning. This Is the Power of Walter Lewin... :)
the example of the two cars bound together by a spring is AWESOME, because it shows a system that doesn't behave like a rigid solid, where the cm is not an actual point of the two cars. So let cm be a point that behaves so that M*r_cm=sum(m_i*r_i) where m_i are held together by bond forces, not necessarily rigid ones. Beautiful example!
@@lecturesbywalterlewin.they9259 Human’s life is limited but what they contribute to the world is eternal. Your lectures in Physics will change the world and eternal existence. Thank you so much.!
The experiment at 46:23 CENTRE OF MASS may seem to defy 'physical law' and the prof. BUT it's the irregular camera panning that gives this impression. The poor camera operator was distracted by the bonkers motion of the two cars. It may have been better to keep the camera still, and not zoom in so much. Physics works and I'm still amazed !
two spheres A and B of masses M1 and M2 respectively collide.A is at any rest initially and B is moving with velocity V along x-axis after collision B has a velocity V/2 in a direction perpendicular to the original direction The Mass A moves after the collision in the direction A) theta = tan-¹ (1/2) to x-axis B) theta = tan-¹ (-1/2) to x-axis
Lectures by Walter Lewin. They will make you ♥ Physics. Sir i broken the momentum into x and y axis and took out the required velocity in x-direction and y separately. Then put tan theta = y/x. So the masses cancelled out. And further my y axis velocity came out negative. Am i wrong?
masses cannot cancel out as M2 is not M1. I solved the problem for you which I rarely ever do. *tan(alpha)=M2/2M1* alpha is the angle with the x-axis. This is my last msg on this topic.
First of all, thank you for the awesome lecture on momentum, Dr. Lewin! I absolutely love your lectures and you really do make physics exciting (especially with your examples of momentum in both particles (tiny) and stars (humungous)) It really helps to know the application of momentum. I have a quick question: in the 1D example with the two objects going in the same direction, why does KE decrease again? It makes sense mathematically, but I don't get why that would be the case conceptually? Thanks again.
+Tushar panda Of course the students are allowed to interrupt my lecture. In fact whenever I make a slip on the black board I WANT them to point it out as slips of the pen are difficult to deal with later (slips of the tongue are easy to correct). Yet, no one interrupted me when I made the mistake. However, when I later watched the video I noticed the mistake and I corrected it with some text.
Two questions concerning the center of mass of the racquet you threw upwards: 1) Wouldn't we take gravity as an external force on the badminton racquet? 2) The center of mass of the racquet follows a smooth parabola and changes direction over the course of time. How is the velocity of the center of mass constant?
1. yes gravity is action on the racquet 2. The velocity of the center of mass is NOT constant. The component in the x direction is constant but not in the y direction.
So technically Energy is not " destroyed ", but dispersed in a different form. I think the terms are really important in order to not create confusion.
Hi Professor. First of all thank you so much for allowing us to freely view your lectures, in a way your like the physics teacher I never had. I'm am currently learning about momentum and impulse and have a question that I'm getting conflicted answers to from my textbook, and various sources online. The problem the question stems from is a basic conservation of momentum problem, A gun fires a bullet that has a final velocity of V what is the velocity of the guns recoil is and the kinetic energy of both gun and bullet ( Which end up having different KE) . My book explains this by saying the force the gun exerts on the bullet acts over a shorter distance then the equal and opposite force of the bullet on the gun. But this makes no sense to me for equal and opposite contact forces only exists when two object push or pull on each other so how can this force pair act on the bullet for a different distance then the gun. Google explained it by saying that it was because of the mass difference not the distance. However this would still mean that the work done on each object is equal and opposite which isn't the case in the problem
In the first experiment with the two blocks and the spring, is the spring force an internal force because the spring is in the system. If this is true, then is the springs momentum not accounted for because it’s much smaller than the other values?
Sir, I had a strong temptation to react on this lecture and so am I doing now - you forgot to mention imho a substantial thing and thus where the kinetic energy after the inelastic collison has gone!!! Of course, it decreases but which form it transforms into as the conversation of the total energy always holds!!!
energy can not be destroyed but KE can be destroyed. *Any decrease in KE is a reduction in KE after which it is gone.* You may not like the word "destroyed" - that a matter of semantics.
@@lecturesbywalterlewin.they9259 please sir let help me to understand it.. so when the colision occurs and all the KE was "destroyed" was it really destroyed or was it tranformed to potencial energy? and thank you really much for lectures, i want to study medicine and this really helps me to understand and love physics
@@rihaveinaiba8269 destroyed really means that the kinetic energy was transformed into potential energy as the bodies get deformed during collision and also some of it is lost to heat and sound and also friction converts a lot of K.E. to P.E.. Even in a perfectly elastic collision, though, K.E. isn't constant throughout, as the 2 bodies come closer and the collision starts, due to molecular deformation some K.E. is converted to P.E. but that P.E. again converts back to K.E. because the collision is perfectly elastic. And hence K.E. before and after the collision stays the same but changes during the collision to P.E. So, K.E. can be destroyed by dissipative forces like friction or can be converted to P.E.
Professor Lewin, your lectures have given me a great insight into physics. At 11:12 you asked a question about kinetic energy of the masses. I had a question regarding the same. In the problem, you conserved the momentum of the system. That means that the net external force on the system is zero so the work done by the net force should also be zero and by work energy theorem, the kinetic energy should remain constant. So why did the kinetic energy decrease? Where did the energy go?
total mechanical energy is conserved. PE (spring) + KE of the 2 masses is conserved. Work Energy Theorem on each mass tells you the change in KE of each mass. Net force on the center of mass is zero all the time. Work energy theorem tells you that KE of center of mass never changed; it remains zero throughout.
8.01 Physics Hans C. Ohanian 2nd edition W.W. Norton & Company ISBN 0-393-95748-9 8.02 Physics for Scientists & Engineers by Douglas C. Giancoli. Prentice Hall ISBN 0-13-021517-1 8.03 Vibrations and Waves by Anthony French CRC Press ISBN 9780748744473 8.03 Electromagnetic Vibrations, Waves and Radiation by Bekefi and Barrett. The MIT Press ISBN 0-262-52047-8
Hey there professor! I really loved your videos. However, can we really say energy is destroyed? I thought energy only can be transformed and transferred.
Life Lyrics you could say that mechanical energy is destroyed (since it’s not conserved), but you’re correct that it’s not really destroyed. Rather, it’s transformed into internal thermal energy and transferred to the surroundings as heat and sound waves.
@@dustinl2375 In the real world, this would be the case. However, here we are doing the calculations based on ideal conditions, and so there should be no energy loss. I can understand when the energies get cancelled out due to opposite direction, but getting cancelled in the same direction confuses me.
What would happen if you could amplify the mass inside of a particle inside of the overall mass that was being exhilarated from outside forces then would it be possible to exaggerated that particle beyond the original mass that it was a part of
Sir, if a ball in projectile motion hit the ground and lost half of its kinetic energy . Will the momentum be conserved in x direction ( since there is no external force in x direction)
Humble hello hello hello Sir, horizontal velocity is same in projectile motion , now after collision force acts normal to the ground so total exernal force in x direction is zero so momentum in x direction should be conserved..
Namaste 🙏🙏 🙏 sir Remember in 1st lecture you stated that Scaling factor Using femur example Can you please explain me That how thickness of femur of an animal would increase by 1000 times When length of femur is increased by 10 times Or the size of animal is increased by 10 times
lecture 14,why bounce ball gives light:When you hold a ball above a surface, the ball has potential energy. Potential energy is the energy of position, and it depends on the mass of the ball and its height above the surface. The formula for gravitational potential energy is PE = mgh where m is the mass of the ball measured in kg, g is the gravitational acceleration constant of 9.8 m/se c2 , and h is the height of the ball in m. As the ball falls through the air, the potential energy changes to kinetic energy. Kinetic energy is energy of motion. The formula for kinetic energy is KE=1/2 mv 2 , where m is the mass in kg and v is the velocity in m/sec 2 . Both potential and kinetic energy have units of Joules (J). As the ball falls through the air, the Law of Conservation of Energy is in effect and states that energy is neither gained nor lost, only transferred from one form to another. The total energy of the system remains the same; the potential energy changes to kinetic energy, but no energy is lost. When the ball collides with the floor, the ball becomes deformed. If the ball is elastic in nature, the ball will quickly return to its original form and spring up from the floor. This is Newton's Third Law of Motion- for every action there is an equal and opposite reaction. The ball pushes on the floor and the floor pushes back on the ball, causing it to rebound. On a molecular level, the rubber is made from long chains of polymers. These polymers are tangled together and stretch upon impact. However, they only stretch for an instant before atomic interaction forces them back into their original, tangled shape and the ball shoots upward. You may be wondering why the ball does not bounce back to its original height. Does this invalidate the Law of Conservation of Energy? Where did that energy go? The energy that is not being used to cause motion is changed to heat energy or sound energy. After playing a game of tennis or racquetball, you will notice that the ball is warmer at the end of the game than at the beginning because some of the motion energy has been changed to heat energy. Because bouncy balls have tightly linked polymers, most of the energy is transferred back to motion so little is lost to heat or sound energy, and the ball bounces well. This is the way the Happy Ball behaves. The Sad Ball has different characteristics. When it is dropped from the same height onto the same surface, it does not bounce even though it has been given the same amount of potential energy as the Happy Ball. It does not bounce because it is made up of a different material. Unlike the Happy Ball which is made of Neoprene, or common rubber, the Sad Ball is made of Norbonene. On a molecular level, Norbonene is different from Neoprene because Norbonene's polymers are more loosely arranged and rub together more when the ball deforms. This additional movement results in motion being converted to heat energy; instead of the ball bouncing, it gets warm. There are several ways to make the Sad Ball happy. One way is to change the temperature of the ball. When the Happy Ball is cooled, its molecules are not as flexible, causing the ball to rebound a smaller distance. When the Sad Ball is cooled, the Norbonene polymer does not deform as much, so less energy is converted to heat energy and the ball bounces. If the Sad Ball is heated, the same process occurs and the ball bounces. Neoprene and Norbonene have many uses besides bouncy balls. Neoprene is commonly used for wire and cable jacketing, automotive gaskets, seals, hoses and tubes, power transmission belts, foamed wet suits, latex gloves and balloons, as waterproof membranes, and for asphalt modification. Neoprene is flexible in its uses because it resists degradation from the sun, ozone, and weather. It performs well when in contact with oil and chemicals and is useful over a wide temperature range. It also resists burning better than exclusive hydrocarbon rubbers and resists damage caused by flexing and twisting. Doping of the Neoprene polymer allows for more versatility and optimal performance. Norbonene rubber has impact absorption uses. It is used as a damping material in shock absorbers and for the protection of conveyor mechanisms. It is used as a padding material in items such as body armor, helmets, sports gloves and mitts, and in the soles of shoes. It is also widely used as an industrial packing material. Stereo speakers make use of Norbonene to minimize resonance and external vibration. Happy and Sad Balls behave differently in a variety of situations. They roll down a ramp at different speeds, they emit sound waves at different decibels, and they bounce different heights on different surfaces. They can be compressed dissimilar amounts when the same force is applied and they are different densities, so they sink in different solutions at variable rates. Allow students to play with the balls for a while and experiment with dropping and rolling the balls to allow them some time to compare and contrast the behavior of the balls and for creative ideas to occur. The time frame for completing the lab is approximately 90 minutes, although this can be modified by reducing the temperatures tested to three instead of five, or splitting the class into 5 groups where each group tests only one temperature and then places their results on a class data table. Achieving exact temperatures is unnecessary; near 00C and near 1000C are easy to get through the use of ice and by boiling water. Room temperature is near 200C.
since in vertical direction there is external force mg on mass m then how conservation of linear momentum is applicable I saw a problem of measuring the speed of bullet by firing in vertically suspended Bob of mass m by a string. then applying conservation of momentum principle give the result. but how since there is external force in vertical direction
The net external force in the vertical direction on each "car" is zero. Gravity downward (mg), force from the track upwards (mg). Thus momentum is conserved in the y direction for each car separately and it is conserved in the x-direction for the 2-car system.
I have a question for you. This question looks at two things, relativity and the conservation of energy. Suppose there are only two objects in the universe, an asteroid and a rocket. The rocket is sitting ontop of the asteroid and they are both stationary relative to each other. Now imagine the rocket accelerates to 99% the speed of light relative to the asteroid (keeping in mind that would require energy to accelerate it). And now lets imagine the asteroid accelerates to 99% the speed of light also and the two objects are now again stationary relative to each other. My question is, now can the rocket once again accelerate to 99% the speed of light relative to the asteroid and can the two objects now repeat this process? If so, now imagine another inertial frame of reference is made, perhaps a planet in the distance, or a moon or even a speck of dust, how would that object view the velocities of the two objects?
Objects, like many faint galaxies in the Hubble Deep field were at a distance of about 13 billion light years from us when they emitted the light. Even though their speeds away from us were a sizable fraction of the speed of light, the light would still travel to us with the speed of light. Since then they have moved substantially due to the expansion of space. They are now 45 billion lyr away from us and their speed relative to us is much larger than the speed of light. The light from them still travels to us with the speed of light but due to redshift, the wavelength is now infinitely high. Thus we see NOTHING!
professor on 14:19 slide you said that if the direction of two bodies change (i.e opposite to each other) then k.E after collision changed , my question "IS k.E before collision will also change due to opposite direction of velocity & it will not not be 21.5J any more ". sorry i am confused at this point
Hello Professor Do the velocities of the cars on the airtrack depend on where along the spring you cut? Supposing you cut the spring at a position closer to one car than the other, what effect does it have on the measurements? I realized you cut the spring at the centre all the time. Any reason?
Professor, after watching your content I have become more confident in exploring and decoding the subtleties of physics in everyday life. Regards from India.
:)
thank you for letting me understand physics! it felt nearly impossible until I was directed to watch your videos by my professor at community college amidst covid-19.
Excellent!
I hope your channel can come to more people in my country
A lot of students in my country don’t know how to learn physics correctly. Therefore they can not know the beauty of physics.
Last 1 year, i hate physics and don’t know how to learn. But now you light up my light, my best teacher.
I hope i can continue your job in order to make physics shine again in my country.
I am feeling like taking up a career in research in physics, instead of engineering now....after watching your wonderful lectures.
Thank you Professor...
Idk how but in one hour you present the concepts better than my teacher does in 2.5 h; u make physics look fun and interesting!
You clarified a confusion of mine which was almost 2 years old... I'm in tears prof...
Hi Indian fella
I have fallen in love with physics now 💖💖💖, thanks sir. Truly a legend. Love from India
All the best
I just wanted to thank you, you’re a big part of why I’m majoring in physics and you really inspire me sir
Dear Professor
I really would like to thank you so much, your lectures and your way of teaching impressed me from the first time I saw your lectures a few years ago, and each time I see them again, I feel the same excitement as the first time when I saw them. So I hope to be like you someday.
You are very welcome
Regards from India, sir. I am a young 15 year old student and I loved your lecture . I now know why people apprectiate your love for physics !
I'm currently an 11th grader, I find physics an interesting subject and wish to be a physicist but a majority of people from my area view physics only as a subject where they need good score to either become a doctor or an engineer, before watching this lecture, I was learning about classical mechanics from another teacher from my country, and to my shock all he did was show some mcqs on the screen and tell the answer without even explaining how he got them, all he said was"This is a very important question which will be definitely coming in your exams, learn it by heart, note it down or take a screenshot", like dude, are we only studying for the sake of exams? I got really frustrated and then remembered about Walter Lewin's lectures. I'm so glad to have remembered about it and very grateful for these amazing series of lectures.
many years later, and you still teach us all concepts of physics in a very easy and intuitive way. thank you professor
Hi, I'm in the high school where we don't learn much, so I watch your lectures which they taught me that physics is even more wonderful than I taught. Thanks for sharing them for free! Best regards, not from India, but from Slovenia!
Sir! you're such a great professor. I think you should live 300 years.
in which country sir is
@@girishsir2442 u can use google;
@@girishsir2442 bruh he teaches at mit, *masachustes* institution of technology, America
Sir, I am not only in love with Physics, i am also in love with your teaching style. Thanks a lot for inspiring us! God bless you!
Thanks for your kind words
Thanks Mr Walter lewin Sir You are a great teacher I am A jee Aspirant 🙏🏻thanks a lot sir.
It's my pleasure
"Thank u sir for making the lecture so good"
THERE IS SOME SPECIAL FEELIN YOUR LECTURES THAT MAKES PHYSICS LOOK MORE BEAUTIFUL. 😊😇😊
"You made my day, because i was struggling to understand these topics"
LOVE FROM INDIA🇮🇳
How good is this guy!?? His talent, passion and attention to detail is something i will aspire to achieve. Thank you so much for sharing these lectures
No one can ever explain any better than this. Wonderful lecture.
Thank you, how can I ever thank you!!
My jee exams are coming, and this topic was ghastly for me, as is for most students I believe. And honestly the first lecture series I watched from you. Thank you. I am crying.
Hi bruh
"Enjoy the presence of your parents" - See you on monday :-)
@Hunter Noe let me help u : wow it only took me 10 mins! it worked !
I love each one of your lessons, each one! It is way better than watching a Hollywood movie. Thank you
I'll never be able to play Angry Birds again after watching this....
🙂🥲
lmaoo, just like how majoring in physics will stop you from enjoying action movies forever
It would be a perfect world if teachers did one solid and always supported the theory they present with actual practical examples, just like professor Lewin. This is how you teach physics, you predict, you show, there you go!
Its really gobsmacking that you are so equivocal about the contents and the way you teach ,that exhilaration in you is just amazing sir.Hats off!!!!
Love from India!
Will really love to meet you some day
:)
38:52 that derivation made my day, i am very satisfied i always use to wonder how people simulated motion of 3D objects , but now i know if i can parameterize the surface of 3D object i can simple calculate a higher integral and find the center of mass and translate that origin of the object with respect to only the force at center of mass of the object :)..very interesting.
Omg, 25000 dollars of tuition and Im watching it for free, thankyou so much Sir Lewin
Your report card is ultimately what you are paying for, when you attend college.
*8.01x Lecture 15*
----
0:05 momentum
4:30 conservation of momentum
6:30 example 1
11:00 about kinetic energy before & after
(Real big deal in Physics)
20:00 never confuse momentum vs kinetic energy
23:10 hold m1&m2 by a compressed spring
28:00 air track
36:00 centre of mass
41:20 find centre of mass
46:13 motion of centre of mass
50:00 tennis racket trajectory
*see more here:*
zyzx.haust.edu.cn/moocresource/data/20080421/U/01220/OcwWeb/Physics/8-01Physics-IFall1999/VideoLectures/detail/Video-Segment-Index-for-L-15.htm
-----
*We love the way you make Physics interesting!*
🌻
Wow I just found this channel after I search on google best physics professor bcz my favourite subject is physics and it's really best lectures and best teaching way ❤️. Thanks walter lewin for this. Now I'm gonna watch whole videos. So much respect from india🙏.
Professor can you please give some tips for jee advanced aspirants ???
Watch all my 94 MIT course lectures. Start with 8.01, then 8.02, then 8.03. Do all the homework and take all my exams. *I guarantee you that you will then do very well on the Physics portion of any freshman college or JEE exam*
@@lecturesbywalterlewin.they9259 First of all thanks for replying 🙏
Surely I will watch all lectures:))
I hope I will meet you once in my lifetime:)))
Thanku very much professor I hope it would help me for jee exam
Thank you professor ❤
Today i accidentally found your channel and it really helps me lot
:)
Happy to hear that!
No replacement of u sir as u are a unique professor in this universe 👏👏👏
Hi professor , I am in class 9th and I can understand what you had explained because of your way of explanation. Thanks a lot 😊. Love from India
You are welcome!
this is the best lecture i have ever watched on centre of mass . it is indeed amazing .
Big fan professor from India. It helps me a lot cause I am also a jee aspirant. Be very happy in life.
I start smiling after realising that
World's best physics teacher is my friend 😊😊
Never new physics was this fun..l just fell in love with physics from lecture by you..love from Fiji❤
Such a great explanation, hats off to you sir. Now I am trying to relate physics to this great world. I feel very thankful to you sir. 🙏🙏🙏🙏🙏🙏🙏🙏🙏
It's my pleasure
I always had something special feeling for physics, and Professor Walter Lewin sir, you have amplified it entirely, now I love physics and wanna persuit a career in it...
Sir but I have been confused of its job market, please sir give me some advise❤
I cannot advise you. I was made for Physics, thus I had no choice
@@lecturesbywalterlewin.they9259 please sir I need a Professional like you to give me an honest advise😢
Shall I not go for it even I love it?
Btw, thanks for your reply... Love from Bangladesh ❤❤
Thankyyou MIT and professor Walter Lewin sir for providing these video lectures free of cost and thereby helping many physics enthusiasts.
Dear Walter, Thank you for these video lectures. I don't understand the math ( mostly at all ) but I feel I'm learning. This Is the Power of Walter Lewin... :)
I wish that one day I will teach my students like you , and show them the beauty of physics, thank you professor
Thank you sir, without your lectures I wouldn't have taken more interest in physics. Now I aslo love physics.❤️
Well, I have not paid 25k ¡
I can enjoy this video when ever I want.
Love you Legend ❤️
Thank you. The knowledge about momentum and its conservation has turned out to be beautiful and profound for me!
*Professor Walter Lewin, You make the world better!*
u2 bcoz of your useful contributions
Your experiment speaks more than your equation professor.
From Nepal
that's my magic
Thank you for uploading this course on UA-cam. Education must be free !
You bet!
I can just wonder if you and Professor Strang have any idea of how precious these recorded lectures are
*yes we both know*
Students pay 50000 dollars for this. And luckily we are watching it free. Great
Sir I think ..............you are best teacher in universe ...I am in class10 but....I could able to understand it......thankss sir
I am very happy because i find this channel, thank you professor :) i in grade 11 from Arabic country.
That's great!
the example of the two cars bound together by a spring is AWESOME, because it shows a system that doesn't behave like a rigid solid, where the cm is not an actual point of the two cars. So let cm be a point that behaves so that M*r_cm=sum(m_i*r_i) where m_i are held together by bond forces, not necessarily rigid ones. Beautiful example!
I should be able to like this lecture twice.
How beautifully you explained it.ありがとう WALTER せんせい
:)
oh.. I really became the best follower of teachers after watching your video lectures.thanks sir🕴
I always feel refreshed after watching your lectures!
35:47 Centre of mass begins
Thanks to our teacher, education is free
thank you for your very useful contributions
@@lecturesbywalterlewin.they9259
Human’s life is limited but what they contribute to the world is eternal. Your lectures in Physics will change the world and eternal existence.
Thank you so much.!
2018, and 25K tuition sounds like a bargain **if I get in**
It's been 3years, did you get in??
The experiment at 46:23 CENTRE OF MASS may seem to defy
'physical law' and the prof. BUT it's the irregular camera panning
that gives this impression. The poor camera operator was
distracted by the bonkers motion of the two cars. It may have
been better to keep the camera still, and not zoom in so much.
Physics works and I'm still amazed !
Sir we really appreciate your technique of teaching physics it really makes me to love with physics
Excellent lecture on concept of momentum Sir. Thanks and Regards 🙏🙏🙏🙏🙏🙏🙏🙏🙏🙏🙏🙏🙏
34:37 Even the best of us made mistake
Thanku professor So much.... Got more interested in physics because of you.. Respect and regards from India.. 😇😇
Glad to hear that
I come here to see this lecture from physics wallah after watching lectures of physics from physics wallah....and this was fabulous lecture
20:53 when u realize u have to submit 4 Philosophy assignments by tomorrow.... rip
It was such an amazing lecture. I really enjoyed ☺ it
Glad you enjoyed it!
two spheres A and B of masses M1 and M2 respectively collide.A is at any rest initially and B is moving with velocity V along x-axis after collision B has a velocity V/2 in a direction perpendicular to the original direction The Mass A moves after the collision in the direction
A) theta = tan-¹ (1/2) to x-axis
B) theta = tan-¹ (-1/2) to x-axis
both are wrong!
Lectures by Walter Lewin. They will make you ♥ Physics.
Other two are C) same aa body B
D) opposite to the B
option E) tan(alpha)=M2/2M1 alpha is angle with x-axis
Lectures by Walter Lewin. They will make you ♥ Physics.
Sir i broken the momentum into x and y axis and took out the required velocity in x-direction and y separately. Then put tan theta = y/x. So the masses cancelled out. And further my y axis velocity came out negative. Am i wrong?
masses cannot cancel out as M2 is not M1. I solved the problem for you which I rarely ever do. *tan(alpha)=M2/2M1* alpha is the angle with the x-axis. This is my last msg on this topic.
First of all, thank you for the awesome lecture on momentum, Dr. Lewin! I absolutely love your lectures and you really do make physics exciting (especially with your examples of momentum in both particles (tiny) and stars (humungous)) It really helps to know the application of momentum.
I have a quick question: in the 1D example with the two objects going in the same direction, why does KE decrease again? It makes sense mathematically, but I don't get why that would be the case conceptually? Thanks again.
how many minutes into the lecture?
around 11:15
the problem started around 6:42
KE will increase and decrease. After all this is a SHM. But the sum of KE and PE will be conserved.
Walter Lewin Sir ..you are awesome. .thank you...
+Tushar panda Thank you
Can't the students point out anything during the lecture...for example the calculation mistake at 34:34???
+Tushar panda Of course the students are allowed to interrupt my lecture. In fact whenever I make a slip on the black board I WANT them to point it out as slips of the pen are difficult to deal with later (slips of the tongue are easy to correct). Yet, no one interrupted me when I made the mistake. However, when I later watched the video I noticed the mistake and I corrected it with some text.
Hello sir ,ur video lectures are very much beneficial for Indian IITJEE advanced exam...
Keep watching
another day went well! Thanks to you, Now physics is a full time fun
Great to hear!
3:52 got mogged while studying physics online
🤫🧏
Sir what about *the Blackbird* which says it *doesn't follow conservation of momentum* (I saw a video on this on Veritasium)
Two questions concerning the center of mass of the racquet you threw upwards:
1) Wouldn't we take gravity as an external force on the badminton racquet?
2) The center of mass of the racquet follows a smooth parabola and changes direction over the course of time. How is the velocity of the center of mass constant?
1. yes gravity is action on the racquet
2. The velocity of the center of mass is NOT constant. The component in the x direction is constant but not in the y direction.
So technically Energy is not " destroyed ", but dispersed in a different form. I think the terms are really important in order to not create confusion.
An air hockey table is a good way to achieve minimal friction for moving objects and it can move the object in 2 dimensions.
Hi Professor. First of all thank you so much for allowing us to freely view your lectures, in a way your like the physics teacher I never had. I'm am currently learning about momentum and impulse and have a question that I'm getting conflicted answers to from my textbook, and various sources online. The problem the question stems from is a basic conservation of momentum problem, A gun fires a bullet that has a final velocity of V what is the velocity of the guns recoil is and the kinetic energy of both gun and bullet ( Which end up having different KE) . My book explains this by saying the force the gun exerts on the bullet acts over a shorter distance then the equal and opposite force of the bullet on the gun. But this makes no sense to me for equal and opposite contact forces only exists when two object push or pull on each other so how can this force pair act on the bullet for a different distance then the gun. Google explained it by saying that it was because of the mass difference not the distance. However this would still mean that the work done on each object is equal and opposite which isn't the case in the problem
In the first experiment with the two blocks and the spring, is the spring force an internal force because the spring is in the system. If this is true, then is the springs momentum not accounted for because it’s much smaller than the other values?
Sir, I had a strong temptation to react on this lecture and so am I doing now - you forgot to mention imho a substantial thing and thus where the kinetic energy after the inelastic collison has gone!!! Of course, it decreases but which form it transforms into as the conversation of the total energy always holds!!!
KE energy loss is converted to heat
14:58 kinetic energy cannot be destroyed, Sir. Instead, it can transform from one form to another. -> Law of Conservation of Energy
energy can not be destroyed but KE can be destroyed. *Any decrease in KE is a reduction in KE after which it is gone.* You may not like the word "destroyed" - that a matter of semantics.
@@lecturesbywalterlewin.they9259 please sir let help me to understand it.. so when the colision occurs and all the KE was "destroyed" was it really destroyed or was it tranformed to potencial energy?
and thank you really much for lectures, i want to study medicine and this really helps me to understand and love physics
@@rihaveinaiba8269 destroyed really means that the kinetic energy was transformed into potential energy as the bodies get deformed during collision and also some of it is lost to heat and sound and also friction converts a lot of K.E. to P.E.. Even in a perfectly elastic collision, though, K.E. isn't constant throughout, as the 2 bodies come closer and the collision starts, due to molecular deformation some K.E. is converted to P.E. but that P.E. again converts back to K.E. because the collision is perfectly elastic. And hence K.E. before and after the collision stays the same but changes during the collision to P.E. So, K.E. can be destroyed by dissipative forces like friction or can be converted to P.E.
Professor Lewin, your lectures have given me a great insight into physics. At 11:12 you asked a question about kinetic energy of the masses. I had a question regarding the same. In the problem, you conserved the momentum of the system. That means that the net external force on the system is zero so the work done by the net force should also be zero and by work energy theorem, the kinetic energy should remain constant. So why did the kinetic energy decrease? Where did the energy go?
total mechanical energy is conserved. PE (spring) + KE of the 2 masses is conserved. Work Energy Theorem on each mass tells you the change in KE of each mass. Net force on the center of mass is zero all the time. Work energy theorem tells you that KE of center of mass never changed; it remains zero throughout.
@@lecturesbywalterlewin.they9259 Thank you professor.
5:15 Certainly, Physics surprises ones a lot!
Being a jee aspirant 😅 studying university physics cause physics is ❤
Our generation's Feynman
:)
Thank you for yoour compliment!
Lectures by Walter Lewin. They will make you ♥ Physics. You really help me wish my physics teacher was as good as you
Lectures by Walter Lewin. They will make you ♥ Physics. Sir can you tell me which book to solve with this course it would be of great help. :)
8.01
Physics
Hans C. Ohanian
2nd edition
W.W. Norton & Company
ISBN 0-393-95748-9
8.02
Physics for Scientists & Engineers by Douglas C. Giancoli.
Prentice Hall
ISBN 0-13-021517-1
8.03
Vibrations and Waves by
Anthony French
CRC Press
ISBN 9780748744473
8.03
Electromagnetic Vibrations, Waves and Radiation
by Bekefi and Barrett.
The MIT Press
ISBN 0-262-52047-8
Hey there professor! I really loved your videos. However, can we really say energy is destroyed? I thought energy only can be transformed and transferred.
Life Lyrics you could say that mechanical energy is destroyed (since it’s not conserved), but you’re correct that it’s not really destroyed. Rather, it’s transformed into internal thermal energy and transferred to the surroundings as heat and sound waves.
@@dustinl2375 In the real world, this would be the case. However, here we are doing the calculations based on ideal conditions, and so there should be no energy loss. I can understand when the energies get cancelled out due to opposite direction, but getting cancelled in the same direction confuses me.
At 37:00 I am lost, why do we multiply the position vector by mass?
That;s the way the center of mass is defined. t
Okay, thanks.
Sir i am neet aspirant
You lectures help a lot❤
What would happen if you could amplify the mass inside of a particle inside of the overall mass that was being exhilarated from outside forces then would it be possible to exaggerated that particle beyond the original mass that it was a part of
how do you amplify a mass?
@@lecturesbywalterlewin.they9259maybe in a hypothetical condition
5:17 same bestie, same
ua-cam.com/users/shortsesyw1xihCWk
i was not even born when he gave this lecture.....
Sir,.if a body always get a force normally when thrown on a plane then why does it not move perpendicular to the plane ?
I wish I was this excited to learn. I'm burned out.
Sir, if a ball in projectile motion hit the ground and lost half of its kinetic energy . Will the momentum be conserved in x direction ( since there is no external force in x direction)
if it hits the ground at an angle momentum in x-dir will not ne conserved
Thank you sir, but why does not momentum conserved In that condition ?
@@prafullakalita1378 momentum is then not conserved in the x-direction THINKKKKKKKKKKKKKKKKKK
Humble hello hello hello Sir, horizontal velocity is same in projectile motion , now after collision force acts normal to the ground so total exernal force in x direction is zero so momentum in x direction should be conserved..
@@prafullakalita1378 yes you are ritgh if no KE is lost momentum will be conserved in the x direction but not in the y-dir
Namaste 🙏🙏 🙏 sir
Remember in 1st lecture you stated that
Scaling factor
Using femur example
Can you please explain me
That how thickness of femur of an animal would increase by 1000 times
When length of femur is increased by 10 times
Or the size of animal is increased by 10 times
lecture 14,why bounce ball gives light:When you hold a ball above a surface, the ball has potential energy. Potential energy is the energy of position, and it depends on the mass of the ball and its height above the surface. The formula for gravitational potential energy is PE = mgh where m is the mass of the ball measured in kg, g is the gravitational acceleration constant of 9.8 m/se c2 , and h is the height of the ball in m. As the ball falls through the air, the potential energy changes to kinetic energy. Kinetic energy is energy of motion. The formula for kinetic energy is KE=1/2 mv 2 , where m is the mass in kg and v is the velocity in m/sec 2 . Both potential and kinetic energy have units of Joules (J).
As the ball falls through the air, the Law of Conservation of Energy is in effect and states that energy is neither gained nor lost, only transferred from one form to another. The total energy of the system remains the same; the potential energy changes to kinetic energy, but no energy is lost. When the ball collides with the floor, the ball becomes deformed. If the ball is elastic in nature, the ball will quickly return to its original form and spring up from the floor. This is Newton's Third Law of Motion- for every action there is an equal and opposite reaction. The ball pushes on the floor and the floor pushes back on the ball, causing it to rebound.
On a molecular level, the rubber is made from long chains of polymers. These polymers are tangled together and stretch upon impact. However, they only stretch for an instant before atomic interaction forces them back into their original, tangled shape and the ball shoots upward.
You may be wondering why the ball does not bounce back to its original height. Does this invalidate the Law of Conservation of Energy? Where did that energy go? The energy that is not being used to cause motion is changed to heat energy or sound energy. After playing a game of tennis or racquetball, you will notice that the ball is warmer at the end of the game than at the beginning because some of the motion energy has been changed to heat energy. Because bouncy balls have tightly linked polymers, most of the energy is transferred back to motion so little is lost to heat or sound energy, and the ball bounces well. This is the way the Happy Ball behaves.
The Sad Ball has different characteristics. When it is dropped from the same height onto the same surface, it does not bounce even though it has been given the same amount of potential energy as the Happy Ball. It does not bounce because it is made up of a different material. Unlike the Happy Ball which is made of Neoprene, or common rubber, the Sad Ball is made of Norbonene. On a molecular level, Norbonene is different from Neoprene because Norbonene's polymers are more loosely arranged and rub together more when the ball deforms. This additional movement results in motion being converted to heat energy; instead of the ball bouncing, it gets warm. There are several ways to make the Sad Ball happy. One way is to change the temperature of the ball. When the Happy Ball is cooled, its molecules are not as flexible, causing the ball to rebound a smaller distance. When the Sad Ball is cooled, the Norbonene polymer does not deform as much, so less energy is converted to heat energy and the ball bounces. If the Sad Ball is heated, the same process occurs and the ball bounces.
Neoprene and Norbonene have many uses besides bouncy balls. Neoprene is commonly used for wire and cable jacketing, automotive gaskets, seals, hoses and tubes, power transmission belts, foamed wet suits, latex gloves and balloons, as waterproof membranes, and for asphalt modification. Neoprene is flexible in its uses because it resists degradation from the sun, ozone, and weather. It performs well when in contact with oil and chemicals and is useful over a wide temperature range. It also resists burning better than exclusive hydrocarbon rubbers and resists damage caused by flexing and twisting. Doping of the Neoprene polymer allows for more versatility and optimal performance. Norbonene rubber has impact absorption uses. It is used as a damping material in shock absorbers and for the protection of conveyor mechanisms. It is used as a padding material in items such as body armor, helmets, sports gloves and mitts, and in the soles of shoes. It is also widely used as an industrial packing material. Stereo speakers make use of Norbonene to minimize resonance and external vibration.
Happy and Sad Balls behave differently in a variety of situations. They roll down a ramp at different speeds, they emit sound waves at different decibels, and they bounce different heights on different surfaces. They can be compressed dissimilar amounts when the same force is applied and they are different densities, so they sink in different solutions at variable rates.
Allow students to play with the balls for a while and experiment with dropping and rolling the balls to allow them some time to compare and contrast the behavior of the balls and for creative ideas to occur. The time frame for completing the lab is approximately 90 minutes, although this can be modified by reducing the temperatures tested to three instead of five, or splitting the class into 5 groups where each group tests only one temperature and then places their results on a class data table. Achieving exact temperatures is unnecessary; near 00C and near 1000C are easy to get through the use of ice and by boiling water. Room temperature is near 200C.
Nice try but that's not the way it works.
since in vertical direction there is external force mg on mass m then how conservation of linear momentum is applicable I saw a problem of measuring the speed of bullet by firing in vertically suspended Bob of mass m by a string. then applying conservation of momentum principle give the result. but how since there is external force in vertical direction
The net external force in the vertical direction on each "car" is zero. Gravity downward (mg), force from the track upwards (mg). Thus momentum is conserved in the y direction for each car separately and it is conserved in the x-direction for the 2-car system.
47:03😅u r a gud actor 2🔥
I have a question for you. This question looks at two things, relativity and the conservation of energy. Suppose there are only two objects in the universe, an asteroid and a rocket. The rocket is sitting ontop of the asteroid and they are both stationary relative to each other. Now imagine the rocket accelerates to 99% the speed of light relative to the asteroid (keeping in mind that would require energy to accelerate it). And now lets imagine the asteroid accelerates to 99% the speed of light also and the two objects are now again stationary relative to each other. My question is, now can the rocket once again accelerate to 99% the speed of light relative to the asteroid and can the two objects now repeat this process? If so, now imagine another inertial frame of reference is made, perhaps a planet in the distance, or a moon or even a speck of dust, how would that object view the velocities of the two objects?
ask google or qoura
Objects, like many faint galaxies in the Hubble Deep field were at a distance of about 13 billion light years from us when they emitted the light. Even though their speeds away from us were a sizable fraction of the speed of light, the light would still travel to us with the speed of light. Since then they have moved substantially due to the expansion of space. They are now 45 billion lyr away from us and their speed relative to us is much larger than the speed of light. The light from them still travels to us with the speed of light but due to redshift, the wavelength is now infinitely high. Thus we see NOTHING!
professor on 14:19 slide you said that if the direction of two bodies change (i.e opposite to each other) then k.E after collision changed , my question "IS k.E before collision will also change due to opposite direction of velocity & it will not not be 21.5J any more ". sorry i am confused at this point
It's an inelastic collision. Thus KE is lost.
Thanks sir I have learnt many things from your lecture .
Hello Professor
Do the velocities of the cars on the airtrack depend on where along the spring you cut? Supposing you cut the spring at a position closer to one car than the other, what effect does it have on the measurements? I realized you cut the spring at the centre all the time. Any reason?
as long as the mass of the spring is negligibly small compared to that of the cars, there will be no difference.
Sir thank you very much 😊 i am studying in 9th still I am able to understand everything thank you very much
It's my pleasure