A Simple Proof of Conservation of Energy
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- čas přidán 19. 12. 2014
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Yep. I understood none of that.
Edit: If your immediate response to someone confessing ignorance is to verbally harass or insult that person rather than help them alleviate that ignorance, then I feel sorry for _you_.
Same. And I'm pretty sure I learned this in college already.
This is going to take 3 or 4 re-watches -_-
Really? Or are you just calling for attention?
Kenneth McCormick shut up Kenneth.
Gaius Caligula Why? It was easy. And I'm not a physicist.
I'm sensing a pattern here "I don't understand, therefore video is stupid"... Really internet people?
IMO it's a valid complaint (in this case). This channel takes a physics concept and explains it in about 2 minutes in a way that a layman would understand. Of course there will always be some of those people, but when when there are so many people left confused, like in this case, the video did not do a very good job.
This video was not too great because it required some prior knowlege of the types of energy, some basic calculus, and just general physics beyond the basic high school stuff. It seems quite a number of people here don't have that prior knowlege so the video is slightly pointless to them.
Perhaps your right, there is more here then can be expected to be consumed by joe blow. Sincere confusion i can understand. Mild frustration to be expected. But the part that just rubs me the wrong way is the general OUTRAGE in tone throughout. How dare they produce something beyond my ability to understand!!!
People behave so poorly when their intellect is threatened.
Anan Anwar The frustration I'm seeing is less outrage that someone "threatened" their intellect, and more a frustration that their expectations - in relation to the video - were not met.
The expectation being that, without an in-depth knowledge of calculus, they could at least follow the train of thought that the video takes.
I, for one, found the calculations deeply confusing in places. I'm in an odd position, where I understand and am deeply fascinated by physics, but find myself almost completely unable to comprehend calculus beyond the level the average 15 year old understands.
Which is why I found this particular video to be deeply frustrating.
Thank you, that's exactly what I have been seeing here is well. Psychological projection of one's own inadequacy onto the video. Students do this with teachers every day.
If your feeling is correct, is Mr. Anan Anwar (you) perhaps also sensing a pattern that says "the majority of the people watching dont understand this, therefore the video is upsetting and unpopular"?
A physicist sees a young man about to jump off the empire state building and he yells, "Don't do it! You have so much potential!"
Sorry I had to tell that joke.
I know this is fuckkng old but this should have a lot more likes 😂
Ik it is 4 years old but it is still very funny 😂😂😂
I know this is five years old, but this is a nice comment.
😂nice
Reported to the police.
"The video was too quick", the channel is called "minute physics". Pause, reverse, you can do that.
Gonzalo Ayala Ibarre Are you talking about the length of the video or the content/length ratio of the video?
So, who the fuck actually understood this?
People whom have studied some physics.
and algebra + calculus.
*edit: forgot calculus.*
I am 14, first year in high school and I underatood it fine till he started talking about calculus (which is a subject we will learn this year) so you don't have to major in physics to understand this, all you need is basic knowledge of physics from the first year of IGCSE. And can someone please explain why or which part they couldn't understand in this video which was too hard?
Deli Dumrul if you're american or british and not a AP or IB student thats not calculus, thats pre calculus. Most high schools only offer it as an option after you completed your G12 or Y18 math. So if you played with logs and trig identities and know how to solve trig equations you're probably going to calculus.
***** What? Yes, that was calculus. Taking a derivative is pretty much the closest to the definition of calculus as you can be.
The fact that I think this is intuitive really shows how intuition is really shit. 200 years ago my intuition would never have came to the same conclusion.
200 year ago you did not exist...
Just like special relativity. You start with the idea that light moves at a constant speed (which comes from Maxwell's equations), and then all you need is some high-school level algebra and the Pythagorean Theorem to figure out the exact amount of time dilation due to velocity differences.
And yet it took humanity SO LONG to figure it out XD
Justin Briand oooh boy...
Mattias Berg What is it?
Justin Briand Literal Steve... just walk away. This is clearly over your head...
The calculus proof at the end was much easier to understand
+Ray Louis And it took 20 seconds
+Ray Louis
There is something. . different about your profile picture. I just can't quite put my finger on it.
100% agree. More precise, more understandable, and it took only 20 seconds
Such is the power of math
6ixx
I enjoyed the music though
This is a circular proof; the kinetic energy formula (1/2 m v^2) is made so that it equals the work the force vector sum do on the object. The formula is derived form conservation of energy in the first place. Richard Feynman does a better "proof" in The Feynman Lectures on Physics. See the introduction to energy section.
yeah, and there's no reason to believe the vF from kinetic energy has the same magnitude as the vF of potential energy based on this "proof."
Well, it may not work as an absolute proof if what you say is correct, but it's still a really interesting way of deriving conservation of energy even if it is reverse engineered.
And also there are certain times that the conservation of energy doesn't apply, such as collision. Energy is lost when deforming the object in Newtonian mechanics.
Also doesn't hold for non-conservative potentials.
Derek Leung
The energy is still conserved as heat. Same with air resistance. His equation just skipped the thermal energy part.
Everyone's saying this video is going to fast or too complicated whereas I pressed "dislike" for very different reasons.
I was able to follow it just fine but I get it can be quite over the top.
This is the kind of video where crucial information has been discarded in favour of shortening it down. At least, that's my view on the matter.
agreed
Heh...get it...view on the "matter"...cuz physics...and matter...no? okay.
DeMizeM4dness :3
I don't think that's how "over the top" is used. That would imply the video did too much to explain things, but I think you just meant complicated. The stuff being explained in this video probably can't be explained well in a short amount of time, so I don't blame them too much. The title is a bit misleading, though.
narwhao I used "over the top" regarding the level and density of the information making the video more complicated. I guess I could've phrased it better.
Can't believe I watched this so many times without noticing that extra calc bit at the end, that was really cool are there more minutephysics vids with that? :-)
No Name Sharma What do you mean by extra calc?
I meant that clarification of the proof using Calculus in the last few seconds of the video :-)
No Name Sharma There was no calculus in this video...
Very end of it, he did it fast so pausing was necessary but I greatly appreciated it :D
Yeah, I looked over it again as per your claim. No calculus.
Thank you very much, MinutePhysics! I love this channel very much! You are doing a great job, and these illustrations are awesome!
I assure you all that I completely understand what I just watched and how it can be used, and by no means was completely confused and stared at my screen with a blank expression the entire time.
Regardless, enjoyable video for sure.
Lol
K, i believe ya.
He didn’t provide any proof. He just used a load of hypotheticals on paper.
Me too
Nine Eleven Also is not true that energy is conserved. Theres no such thing as "conservation of energy" in the universe. The expansion of the universe is an example. Physics should always explain it because everynody seems to be confused with this concept. This is 200% bs. Energy is not conserved at universal scale.
The problem with this video is that it probably won't make any sense to someone who doesn't have a science background, but if you do have a background in science you understand that crucial thermodynamic concepts were omitted - internal energy, pressure, temperature, etc - and thus the "proof" is far from complete.
Brad R If you have that sort of thermodynamics background, you should recognise that those concepts (as far as they relate to energy) are forms of potential or kinetic energy.
You're right, Natasha, but he only considered and presented gravitational potential energy and kinematic kinetic energy. I trust you understand that there is a difference between chemical potential energy and gravitational potential energy? And I assume you know that it's hard to measure the internal energy of an object by directly measuring the velocities of its particles?
A lot of this stuff you do in grade 11 physics
so glad you are still making these frequently
Thank you!!!!!!!!! It took me a while to understand every part of it, but you explained everything very clearly! Please continue with these kind of explanations this is good!
Great job with these mechanics videos! I'd love to see a video tackling the Twin Paradox!
This is amazing. Loved it!!!
Hate you. Just watched bout 10 of his videos after this one.
MinutoDeFísica this has to be ONE OF THE BEST CZcams CHANNELS EVER......AMAZING VIDEO MEN....CONGRATULATION !!!!!!! 100/100 I LOVE THIS VIDEOS....YOU MAKE SIMPLY BUT AMAZING VIDEOS.....LOVE SCIENCE ...KEEP DOING WHAT YOU LOVE
I understood this video better than many of your previous videos, thanks to your simplified proofs :)
I was GOING to take physics during my next semester of college... but now Im thinking ill just take something else.
+Juan Mendoza it's a lot easier if you do it slowly and think about each step
This is middle school physics, mate.
Nah. This is kindergarten physics.
Naaah, It's pregnantgarten physics.
Naaaaah, I knew this stuff in the womb
i understand the conservation of energy part of it, but where do the time zones come into it?!
just to say that if time did matter (as in affecting forces or something) then timezones wouldn't be possible, since everyone would have to read the same time.... or something like that. idk seemed really unnecessary.
ah ok
Kolop315
Right, it was unnecessary. Interpolating some negligible aspect into the explanation just for filler' sake.
see, the thought behind the time zones is that,the weather and atmospheric conditions are different at different parts of the world.so how is the conservation of energy principle valid?See there are two kinds of forces-conservative forces and non-conservative forces.Conservative forces are forces for which we can apply potential energy(like gravity,when you throw a thing up in the air,you give that thing a potential energy and this potential energy gets converted into kinetic energy fully but not accurately..due to drag forces by the wind which take some part of it).And non conservative or the forces which involve large dissipation of energy in the form of heat (like friction,or the electrodynamic field inside a battery)we cannot apply the same conservation of energy concept and so we have to consider the heat too(which is quite difficult to calculate).so at different places on earth, there are conservative,semi conservative or fully non conservative forces.But the total energy doesn"t change with time according to "THE CONSERVATION OF ENERGY".so all the energy provided by all the types of forces even out and we get the same result everywhere.hope you understood what i wanted to tell.if not ask me in the comment
Vibodh Jadhav Still not 100% confident if i had to explain it to someone but your explination makes a lot more sense than the video's. Thanks.
MP I love your videos, and I can't even comprehend the level of difficulty I'm sure lies when trying to simply things like this, but as soon as I saw "simple" in the title I knew I still could come out with nothing after watching
Well presented! Mind blown on how simple you made it.
So, can someone good at physics answer something for me?
Does potential energy actually exist?
The notion of 'potential energy' has always bugged me. It feels like someone realised that the numbers stop working when you take into account gravity, so you have to give everything an imaginary kind of energy to keep everything neat.
If I put a book on a high shelf, does that cold, static object have energy? It doesn't react any differently to a book on the floor and if I move it down there nothing has really changed. There's no measurable difference in an object based on how high up it is.
What happens to objects in space? Or at the Earth's centre? Do they have more kinetic energy because they have no potential energy?
Maybe I'm just super ignorant but this all seems pretty sketchy.
Well, it's like a rubber band. If you stretch a rubber band and keep it stretched, it will keep pulling your hand, and you have to keep it there. The difference with gravity is that a rubber band pulls harder the further you pull away, and with gravity it's the reverse. So you could say that stretching a rubber band takes potential energy, which gets released when you let it spring back into place.
***** ... OH I think I get it? The thing that 'has' the energy is the stronger gravitational force?
Well, that question is something... Haven't thought about it....
So I'll just leave this here to watch the results ^_^
It's potential energy because the higher up object has a higher gravitational potential energy, meaning if it, say falls on a spring, that the spring would coil up more from the gravitational energy than an object dropped at a lower place due to the -9.8m/s^2 acceleration onto earth. Potential energy still acts on objects in space, just in a hugely smaller amount, as gravity attracts matter to one another (and the acceleration towards the object would change from -9.8m/s to another depending on mass). Potential energy is mainly used as a reference when comparing two objects, one at a "ground state" where potential energy = 0 and another at a state of potential energy when PE > 0.
1:40 - 1:56
This video made so much more sense after I started taking physics
Best video on the topic I have seen and it took 1/10th the time of the rest !
I just loved the explanation. ... never had cleared a doubt in such way....... loved it
Before I hit the replay button 17 times, could you make a video on potential energy? That whole thing doesn't make sense to me.
Basics: kinetic energy is moving energy, potential energy is stationary energy. Totally not true, but I just said it like that for the sake of simplicity. So to keep it simple, there is a ball on a string: a pendulum. When it is swinging it has energy right? This is called kinetic energy, aka moving energy. But it didn't just start moving out of nowhere with no energy input. It needed to have potential energy in order to start doing kinetic energy. This potential energy was probably created when somebody took the ball on the pendulum and raised it (most common example). The ball now has potential to fall and start "doing" kinetic energy. This potential is called potential energy. It can be converted into kinetic energy. Just like a potential doctor isnt a doctor yet but it couldnt become a doctor based on its precursors. Bad example I know, but it might help. But dont listen to all I say, this is very basic stuff, do some research for yourself!:)
Hi, potential energy sounds confusing but you see examples of it in your every day life. The best visual example of potential energy is a spring. When you stretch a spring it takes work. The spring fights against you, it does not want to be stretched out. When you let go of the spring it snaps back to normal. What you are doing when you stretch the spring is pumping energy into it. when you let go the spring uses that energy to bring itself back to normal unstretched condition. Kinetic energy is the energy of motion and potential energy is stored energy. When you jump into the air you use energy to gain hight. But as you go up you slow down and then come to a stop. Where did your energy go? When you started your jump you were moving up verry quickly but now your not moving at all. All that energy went into gravitational potential energy. All that meens is that gravity took your energy in your upward motion after you jumped into the air and stored it (temporarily). You only are motionles in the air for just a moment, then you fall back down. When you fall down you gain downward energy of motion. But where did gravity get the energy to make you move quickly in the downward direction? Gravity uses the potential energy it robbed from you initialy. Just to repeat: when you jump you have energy in the form of upward motion. Gravity robs you of this motion bringing you to a standstill in mid air and stores the energy temprarily. Then gravity uses the stored energy to send you quickly back down to the ground.
Isaac Thefallenapple Isaac, the fallen apple has less potential energy. lol
Giles Bathgate Hehe, never thought of that =)
Thank you all for explaining this to me while being nice. I think I got it now.
Didn't you mention in one of your videos that you're a theoretical physicist? If that's true could you make a video about what you do? Like a day in the life of Henry if you will. I want to be a theoretical physicist after I get out of high school and that would really help.
Thank you, now i get what my physics teacher tried to tell us in class. You are awesome, keep up the good work.
Videos like this are why I subscribed years ago. More please.
If you don't understand math, you don't understand physics. This is 8th grade physics. You need to go from superficial understanding to real understanding.
Cool video, but there's an important assumption made here. Namely that the only forces applied are those associated with the potential energies involved. Otherwise the F from the kinetic energy is net force, butd the F from the potential energy is not the net force. The energy of a system can always change, if there is external work done (forces other than those associated with the PE).
In fact this is tautological since we define KE from the idea of the net work done and the work energy principle, and if you define the change in PE as negative the work done by the "net force" then you have simply assumed energy conservation by definition. Basically we got so mixed up with words and language, we thought we said something profound, but really just restated what we already assumed.
Such a simple and elegant solution to a hard problem.
Love these videos. I can tell I'm learning things as I begin to better follow and challenge parts of the videos.
Just a heads up. Seconds 10 to about 30 are the exact reason why conservation of energy isn't exact. There is an absolute zero time (i.e. Big Bang) which ruins this shift in time symmetry. In modern cosmology, "dark energy" is basically accounting for this amount of total energy variation in time.
Huh, I've always just accepted that energy is conserved, I never stopped to think that such an idea had to be proved at some point.
TheJaredtheJaredlong What we've proved is the idea that _if_ physics is the same whenever you test it, then energy is conserved (in fact, we've actually shown that these two statements are _equivalent_). We feel it's a good assumption, though, because if physics _isn't_ the same whenever you test it (to a reasonable approximation), then science is completely unable to explain the Universe.
You can't just accept things to be true, without proving/demonstrating them to be true.
Adam Wojtczak
And this is why I'm not a scientist lol
I wish someone explained this to my this way in high school. This video just made a bunch of concepts fall into place in my mind.
I am going through year 10 Physics and I find this very helpful. Thanks.
So this already-barely followable explanation is actually a shortened version?
The shortest version would be to assert that time symmetry in physics is _equivalent_ to conservation of energy. Explanations of fairly fundamental laws like that tend to become quite in-depth so we can be sure that they're true.
***** its hard to follow if ur stupid
Such a smart reply from such a smart person....
Quick question. At the Calc part, why did he define PE as -integral of F(x)?
F=ma F=mg The sum of all forces F? Downward?
He at no point mentioned, or used the symbol for integrals, nor did he refer to any function. He defined PE as being equal to the force F multiplied by its position x.
phiefer3
You need to be patient and wait till the very END of the video. He started dwelling into other things.
Potential energy is defined as the negative integral of F(x). You can kind of think of it as the summation of all the potential energy in a system equates to the total force.
My major and career is physics and Engineering. Basically to become a physicist, and I have to say you teach physics better than the teachers at my school. So great job!
Finally, the kind of content I've expected out of minutephysics for a long time
Aaaaaaaaarrghh muh braaaayn!!!! It hurtsssssss!!!!!!!
Wait, Audible is back? So what happened to Airbus?
That was a very interesting proof. It's one of the many reasons why I think physics and math are awesome. Keep up the good work, Henry.
So cool! Takes my knowledge of physics to the next level, that's awesome!! :D
Finally some math.
Say that again
Useful clip. Thank you for publishing
im jast learning the same thing at school and your video realy helped me understand it much better than THANK YUO for your GREAT videos
I thought this was a SIMPLE proof.
It is compared to Lagrangian mechanics
It is simple
Charlie Snowball simple in physics isn't simple
It is extremely simple
It's simple when not explained in two minutes
I am actually a physics teacher and though everything shown in this video is correct, it is really really doing a terrible job at TEACHING stuff. You have to be an expert before watching it to just get like 80% of what is said. Instead of just rushing through with some nice pictures along it would be much much better to
1) slow everything down by factor 5
2) explain basic formulas used
3) explain words being used
Then you might be able to actually explain stuff instead of just pretending to be "easy to get".
matyourin He doesn't do 20 minute videos though (which would be the result of slowing it down by a factor of five), so his options were to do it in a manner similar to this, or not do it at all. The latter may have been better, but I guess this is one of those cases where if the audience wants to get something out of it they need to work, rather than expect to passively absorb the information in a qualitative manner.
Natasha Taylor That would have been the better option - not doing it at all. What is the point in an educational video that only those get who already got it? To me this is just another "atom physics explained in 3 minutes" - like video. Looks nice, doesnt acomplish anything...
I was just giving my feedback hoping future videos will be either longer / slower or will deal with adequate questions for this format. Like "why do stones fall down" :)
You are a physics teacher and you are saying that people have to be experts to understand basic conservation of energy??
JAO CAREKA
Heck no! I am saying that "people" have to be experts to understand THIS video.
Of course it is possible to understand conversation of energy, even as a 5 year old. But in this video they rush through and complicate things by mixing everything with relative / absolute time...
There are lots of things you have to know beforehand (just listen to that video again and count how many "expert" terms and formulas are used... I did it just now and found more than 20 things that would need further explanation to make a "non expert" really understand the video.
If I'd try to explain what this video explains to a class of 30 kids, age 15 to 17, it would take roughly 90 minutes to get about 80% to understand it. If I'd show this video to them maybe 1 or 2 of that class would understand basically what they have been shown (though they'd still be unable to explain it to others).
Im in high school, not an expert at all, and got this video in 1 replay..
very cool, i love physics and just topics like this. I had to watch the video a few times though to wrap my head around it as it was rather quickly explained.
Wow! Fantastic proof! I never thought of conservation of energy like that. Very clever
This video made me realize I'm not interested in physics.
This is 11th grade Physics. How are people not understanding something this simple?
***** Because not everyone in this channel did well in algebra, necessarily passed highschool or did so within the past decade. Remember, 'simple' to you is not necessarily 'simple' to everyone else, especially people with a different educational background.
Natasha Taylor Yah, you're right.
Its all sad really.
Because all this is REALLY interesting.
+Natasha Taylor This channel isn't about 'simple' stuff. It never has been. Just look at his proof of e=mc^2 or rocket science videos.
Alex M. You seriously dredged up an eight-month old conversation to make that banal observation, to argue against an assertion never made?
Natasha Taylor The implication in your comment was that there are others in this channel who don't have the same physics background. I'm saying that the target audience isn't for those.
And yes, I respond to comments as I see them.
This video was perfect as the basis of a homeschool science unit on conservation of energy laws. THANK YOU FOR IT!!
MinutePhysics Henry, I really enjoy your videos like this. I am about to get my BS in physics (one more semester) and I am at that point where the connections are being made. This was really awesome and something I am going to bring up with the students I tutor!
Cheers sir. Thank you.
being just an lowly engineer I see two issues with this proof.
First the equations for kinetic and potential energy already anticipate that there is a conservation of energy. so the exercise actually only shows what is our assumption. It is basically circular reasoning, sorry to say that.
Second the universe is expanding. wouldn't this generate kinetic energy which is not already in the system. Two static bodys will separate because there is space generated between them. The potential energy will rise (because they are further apart) and as space is generated evenly in between they will also accelerate.
third, we are aprox 13.7 billion years away from big bang. Total reasonable human history is less then 10k years. So even with history books the time distance difference is miniscule. How are we able to say that it doesn't matter when to start?
Number Three is really a question. Can you answer that please. And can you address #2 as well. In some other video (from University of Nottingham IIRC) it was said that we experience time the way we are because we are so close to big bang. so how can we assume that nature's laws don't change...
Georg Antonischki The formulae for kinetic and potential energy only provide conservation of energy iff physics has time symmetry. That is to say, given how energy is defined, the assumption that energy is conserved is equivalent to assuming time symmetry of physics. If time symmetry is _not_ true, then neither is conservation of energy (we would only see it conserved on scales where time is approximately symmetric).
As for #2, I'm not sure how conservation laws work in general relativity, and so can't help you.
1. Most of science is, when you get down to it, circular reasoning. That's the point. There's a limited amount of simple propositions, relations and laws with which everything else can be proven. All of logic, all of language, pretty much everything that concerns any type of knowledge is inherently circular. When you tell me that London is in the U.K. you're not telling me anything at all. Because if you get down to it, the concept of London already entails it's location on the globe. Same here, you're not incorrect, if you know what energy really means, you would also know why it's always conserved over time in a system. But that's not a sign of a faulty explanation.
2. No, everything we can (so far) see, is moving apart, that's something else entirely. The phrase 'the universe is expanding' is just an oversimplification. There is no definite answer to the question what the universe is doing. One of the assumptions when working with the conservation of energy, is that you're talking about a closed system. Just like the principle of entropy. If you add energy to the system, you can add order and structure, but as soon as the system is closed, the level of entropy will increase. There is no way of saying that the Universe is a closed system. Maybe it is, maybe it's not.
But to get back to your static bodies. They're not static, they've begun moving apart at the big bang. You would be right if they were static, because that would mean that there was some kind of energy added to make their movement possible, but they never were static to begin with. Most people nowadays believe both in the big bang and the big crunch. Which just means that although the universe is expanding, it's expanding at a slower rate than it used to, and it will expand more slowly with every second that passes. The conclusion of course is that the expansion will some day stop, at which point the big crunch will start and everything starts 'falling' back into the point where it all came from.
3. If it looks like it's constant, and it behaves as if it's constant, it's probably constant. We do not have a single reason, not one single empirical fact, to argue that the laws of nature are changing over time. The only thing we don't know for sure are their outcomes in extreme situations (singularities for example). Is it possible that we're wrong? Yes absolutely. Just like we could be all wrong about any given knowledge. God could be real after all and maybe tomorrow everyone grows a pair of wings. But it's simply not logical. It doesn't fall into any reasonable line of expectation. At some point, unless you want to be a solipsist or an extreme skepticist, you need to accept that things are the way they are.
jorgbeijer 1: Gödels incompleteness theorems
Yzal Nosrep Einstein's coffee machine.
...
What's your point?
jorgbeijer
You wrote: "There's a limited amount of simple propositions, relations and laws with which everything else can be proven. All of logic, "
Which can't be done. (to my understanding, please educate me If I'm wrong :) )
mind=blown
penis=notblown
:(
lovingboarding You sir, deserve the nobel price.
lovingboarding Sad Barry. Sad sad Barry :(
lovingboarding there are plenty of men around to help you out
Thanks for explaining conservation of energy in just 4 minutes I had to watch around 30 minutes of lectures to able to get to this in just 4 minutes You really saved my time hence my energy is conserved
Keep doing what you're doing! Greets from Germany
Noether's theorm..
As in No way I'll do a Laplace transform to prove that.
I know I'm 4 years late, but that's Lagrangian.
I feel like you need decent knowledge of physics to understand this video. If you're just curious, but a re not educated in physics then you'll probably not get the point of this. I know i didn't.
Seriously, i can get basic quantum mechanics, but this equation math magic is just too much.
If you don't understand basic math, you surerly don't udnerstand basics of quantum mehcanics.
Basic quantum mechanics requires linear algebra which although not difficult is still a step above the algebra used in this video.
I'm in the exact same boat as you here.
Through several popular science novels, and other educational means - like these youtube videos, I've found myself completely able to comprehend more complex physics concepts - like quantum mechanics. However, I was completely lost by the mathematics used here.
There are ways of explaining physics that don't rely quite so heavily on the use of calculus and - in the places that it is truly needed - there are better ways of explaining those equations to people who struggle with mathematics.
AllannaXD While I definitely agree that there are often better ways of explaining things (especially as it applies to new or different materials), the language of physics is mathematics. There is no way around it. You can understand ideas and concepts, but you will never truly understand physics without a deep understanding of math.
This is because physics is built with math. The people who came up with these laws, were just looking at the mathematics and how the equations worked out. Then they put it into words. The words are meaningless and arbitrary. Physics is just math.
AllannaXD
True, but this is a "proof", not an "explanation"
I'm a Communications student and I actually understood what you just said. Good job.
although my mind lagged in understanding, it caught up and this helped me so much more than my physics teacher did in a year
You lost me at 0:00
In truth actually there is no proof for the law of conservation of energy. What you have shown is by assuming all forces are conservative and that the potential energy of a mass is only its gravitational potential energy.
...Nice video though.
Rishav Koirala What he's really demonstrating (or trying to) is that assuming time symmetry of physics is equivalent to assuming conservation of energy.
Natasha Taylor That, I can agree to.
That moment when its midnight and you drift off while watching this video and you missed half of it
I feel like i understood, my teachers in college teach the same way you do so it's easy for me to follow along. It was an interesting video.
Okay, I need your help to understand something:
I was reading the comments and... Can you please tell me what do you think is wrong with this video ?
I saw a lot of people saying "speak slower", he wasn't speaking faster than in other videos. The others comments are "understood noone of this" and I really don't get this one either because it is one of the most basic physics concept we learn in High School. I was not even student in science and I understood everything without having to pause the video... Can someone explain me what was hard to get here?
The video "solution of the impossible bet" was much harder to understand I think and no one was complaining in the comments.
I think what people don't like here is that it's written "simple proof" in the title
and for this he used lots of hidden physics principles like the kinetic theorem, work of non conservative forces etc etc.
those assumptions are not that obvious
Some people didn't take physics or alegbra in school. Yes, seriously.
The problem with the video wasn't that he was talking too fast. A lot of people didn't understand how this proves Conservation of Energy and probably assumed that speed was the problem. And well the problem really is that it doesn't prove Conservation of Energy. It proves that the energy formulas work under the assumption that Energy is conserved.
paxpacis2 edit: it appears, by the title, that he was trying to prove the conservation of energy. Though it seems like he is trying to prove time invariance of physics more so (ie. that the formula's work regardless of a shift in time) and he used mass-energy conservation to the prove time invariance using an approximation of Noether's Theorem which informally states: "If a system has a continuous symmetry property, then there are corresponding quantities whose values are conserved in time" Though it wasn't as clear as minute physics videos usually are (probably due to the amount of prerequisite knowledge necessary to follow it in such a short time span)
I'd bet quite a bit of money that you can't explain this to me, provided that you don't know physics.
But... Energy is lost by photons redshifting...
+Spiked Blueshell
...and it goes into the vacuum of space. The energy is still there, it's just not in the photon anymore.
***** No it doesn't. Conservation of energy doesn't actually apply to an expanding universe; only to a local inertial reference frame. But this effect can be realized even more dramatically if you think about technically the distance between the protons in atoms, or the atoms in molecules (or even planets and their moons), stays constant over time, even though the space they're in is expanding. So technically energy is being injected because some force (Coulombic, gravitational) is doing work to keep those volumes constant by working against the expanding space. It's just negligible at a local enough scale where you can consider reference frames inertial.
+Spiked Blueshell I was about to mention that.
+Spiked Blueshell Physics Girl?
AlchemistOfNirnroot Yep.
The author goes very fast and he assumes that the viewers already have a good grasp of the subject.
Good thing you can rewind it then..
Finally. Something that I was looking for a while
i still have no idea what the hell this guy is talking about
Basically:
Velocity=Distance/Time ; Measured in Meters per second
Acceleration=The difference between 2 velocities/Time ; Measured in Meters per second squared
Force=Mass*Acceleration ; Measured in Newtons
Work(Used interchangeably with energy)=Force*Distance ; Measured in Joules
Power=Work/Time ; Measured in Watts
Ben Crispe look, im terrible at sience
you kids with your nervutos and two parts Dude its simple High school physics
you kids with your nervutos and two parts He's not good explaining, you have to know these stuff to get the video, i do and i got it... but no one will if he doesnt know
basically used maths to prove maths..
No, its a law in physics....
although i have no idea about all those concepts, i still thank you for sharing this to us :D
hey physics haven't seen this in a while lol love you Henry
I've finished three years of calculus, and I have no fucking idea what is going on in this video.
Kyle MacDonald First off, math and science people are some of the smartest people in history (inventors, philosophers, scientists, etc) - you don't see historians with genius IQs.
Second, this is physics and math is the BASIS of physics, and a big part of that is calculus. And yes, this uses quite a bit of calculus, but I was just saying I have an intelligent basis of math, and I have no idea what happened because he explained it very badly.
Kyle MacDonald Perhaps you didn't understand the "three years of calculus" part I used (yes, I know derivatives and integrals). I was just using that to show I have a basis of knowledge, and yes, that extends beyond calculus.
As for the topic, yes, there is quite a bit of calculus used that is overshadowed by the simplification of the equations.
Also, engineers ARE math students. I didn't say "math majors are some of the smartest kids around" now did I? Perhaps an additional English class would benefit you.
Kyle MacDonald Dentists know a lot about calculus, given that they frequently scrape it off people's teeth.
Kyle MacDonald Someone walks up to you on the street and asks what the integral of x^2 is.
Kyle MacDonald This is a physics video, and the basis of physics of math - and calculus is a big part of that. My comment was merely showing that I have a stronger math background than a lot of other people on this video and I didn't understand what is going on, so it should be dumbed down a bit.
The video is wrong. Not in the mathematical derivation, which is pretty elementary. But conceptually, conservation of energy has absolutely no link with the fact that you cannot set an absolute time, nor with the fact that time zones works. This is just a mistake.
Plus, the video just assumes we know that potential energy cannot be defined when a force varies with time without any explanation. In fact, it's false, there's no problem with the potential energy when a force varies with time, potential energy will just vary with time too.
While I appreciate MinutePhysics efforts to vulgarize some of the most important and beautiful concepts of physics (Noether's theorem in this case), it has to be done properly !
Sékou-Oumar Kaba You're right in that this has absolutely nothing to do with timezones, but you're mistaken about the idea that conservation of energy has nothing to do with time symmetry - Noether's theorem demonstrates that time symmetry and conservation of energy are actually equivalent assumptions (i.e. if you assume one, the other is implied).
No, conservation laws are always due to symmetries in nature, such as the homogeneity of time. Conservation of energy is the homogeneity of time, conservation of momentum the homogeneity of space etc.
Natasha Taylor You are absolutely right but that's not what the video says. As you know, time symmetry is the fact that if you repeat an experience at a different time you will get the same results. In the video there is confusion between time symmetry and change of coordinates. It says (20 first seconds) that you can always set the "0" of time the way you want but that doesn't imply time symmetry. For example, if the gravitational constant were to vary with time, then energy would most certainly not be conserved because a system couldn't be time symmetric. However you'd still be able to translate the time coordinate and set the "0" the way you want.
*****
Same answer
Potential energy is only defined when dealing with conservative forces, which, by definition, only depend on position (and thus not time). So he's right.
This video explained things very clearly, just quite fast. One of the main reasons I like this show is if I get it in a few mins I don't have to spend any more time on the video and if I don't I can just re watch.
But those last few mins would have definitely been helped with more explanation, though I suspect they were put after the ad intentionally in full knowledge most people wouldn't be able to follow them.
1:24 best, clearest definition of potential energy. it's short too. I just wanna say, thanks for helping me learn.
PT Yamin again 2:14 change in position over time is velocity! These are the clearest shortest definitions in ever! Thank you!
PT Yamin Not only is this video a proof of the Conservation of Energy, it helps you understand the definitions of some concepts in physics for those who have not been in a physics class yet but constantly encounter these concepts but never understood what they really meant.
/watch?v=2htckwDkugI this video does the same for momentum
This explanation is valid for a particle moving along a straight line. More complex systems or trajectories would need further explanations.
It also would be nice to mention Noether's theorem, to highlight the connection between symmetries in physical laws and conserved quantities.
I can't believe I studied engineering/physics for so many years without seeing this relationship.
This is really awesome. This makes me wish I was a Physics major.
Holy crap! Beautiful proof! Didnt quite understand the derivative of the PE but seems legit! Beautiful stuff.. Just beautiful
This was a beautiful proof of a very basic, but slightly complex, topic using only basic algebra and the Kinematics equations.
That's really interesting, I wrote a collision engine in my game that works on the same "At any particular time the force must remain the same" idea.
I understood it perfectly. He put it in a dumbed down way.
This is one of the first videos I've completely understood :P (I studied this in school last year)
Good call! It is Indeed beautiful physics.
A lot of people think there is calculus in this video. There isn't. All he did was rearrange an equation and substituted variables. That's all algebra. You don't even need to understand physics at a basic level. He gives you all of the equations and formulas in the video. All you need is a working knowledge of algebra and to watch the video.
There’s a quick calc proof at the end
One powerful equation that results from this is that the change in kinetic energy is equal to the change in gravitational potential energy :D
1/2m(v^2-u^2)=mg(h1-h0) where v=final velocity, u=initial velocity, h1=new height and h0=old height.
This is brilliant! It all makes sense now! I love to live!
Aprendi en 3:57 minutos lo que mi profesor de fisica no pudo hacer en un cuatrimestre entero, como es de importante la forma en que los docentes te pueden motivar a seguir amando tu carrera y el camino que escoges.
I did physics for the Leaving Cert (and higher maths) and my dad is a physicist, but this did go too fast. I understood the concept, having done most of it just a few months ago, but I can only imagine what it was like for those who haven't studied physics in detail. I still enjoyed it, but I think like most, I was just like, 'could you go over that again?'
Nice introduction to the connection betweeen a conservation law and a certain symmetry. In this case we have a symmetry of time translation connected to conservation of energy. Conservation of momentum is related to translation symmetry, and conservation of angular momentum is connected to angle change symmetry. Etc...
Thank you, Henry! :)