The Trick that Makes Understanding Physics as Simple as Drawing a Picture: Physics Help Room

F = ma can be really hard to solve, so it's important to be able to get intuition about a physics system without having to solve F = ma. The trick is to think about the potential energy curve. Get the notes for free here: courses.physicswithelliot.com...
Get the NOTES, the PROBLEM SHEET, the SOLUTIONS, and the ANIMATIONS: www.physicswithelliot.com/pot...
Tutoring inquiries: www.physicswithelliot.com/tut...
If you find the content I’m creating valuable and would like to help make it possible for me to continue sharing more, please consider supporting me! You can make a recurring contribution at / physicswithelliot , or make a one time contribution at www.physicswithelliot.com/sup.... Thank you so much!
About physics help room videos:
These are intro-level physics videos aimed at students taking their first physics classes. In each video, I'll teach you the fundamentals of a particular physics topic you're likely to meet in your first classes on mechanics and electromagnetism.
About me:
I’m Dr. Elliot Schneider. I love physics, and I want to help others learn (and learn to love) physics, too. Whether you’re a beginner just starting out with your physics studies, a more advanced student, or a lifelong learner, I hope you’ll find resources here that enable you to deepen your understanding of the laws of nature. For more cool physics stuff, visit me at www.physicswithelliot.com.

[@olivierrokks]

Bruhhhh, Video, Notes AND Homework??? I love you.

[@EnemyOfEldar]

Dude I got my degree (Msci) in Theoretical Physics 5 years ago and I have been a maths/physics educator since. You're awesome. Keep doing what you're doing. You've just levelled up my teaching for sure and it will make a difference to my students as well. Godspeed, Elliot.

[@PhysicswithElliot]

So glad to hear it!

[@TheAgentJesus]

Dude you are awesome, this is such quality content and exactly the kind of thing I love seeing more of in the educative sphere of KZbin! Thank you so much; do you have a patreon or anything like that?

[@PhysicswithElliot]

Thank you so much! And thank you for asking; creating a Patreon has been on my to do list, and I've just now gone ahead and set it up at Patreon.com/physicswithelliot. Thank you in advance if you decide to be my first patron!! Please also let me know about what other topics you'd be interested in learning about

[@TheAgentJesus]

@@PhysicswithElliot unfortunately I'm a bit strapped at the moment - indeed, I've had to suspend the two or three patreon accounts I'm normally subscribed to; that said, as soon as I'm financially stable again I'll be sure to replace one of them (which is a great channel, but already has plenty of crowd-funding attention and hardly needs my help) with yours so as to hopefully help you with those initial hurdles: you definitely deserve it! I particularly like that you make a point of including problem sets; it's habits like that which could really turn KZbin into more than just "Edutainment," but an actual functional supplement to (or even eventual 'replacement' of) traditional secondary education. So seriously, thanks so much for your effort! Hopefully by the time I come back in a month or so to subscribe I'll find that I'm not the first!

[@PhysicswithElliot]

Not to worry!

[@douglasstrother6584]

Nice! Developing a physical understanding of what a solution should look like using this technique and other graphical approaches is a critical skill. There are about six core problems which can be solved in closed-form; that's one reason why the simple harmonic oscillator is used everywhere! It's amusing that the pendulum can't be solved in closed-form. (The period as a function of angle can be expressed in terms of elliptic integrals.) The three-body problem is also fundamentally intractable. This presentation hints at the concept of Phase Space which is used in Classical, Statistical and Quantum Mechanics.

[@aleksandr_berdnikov]

A trick that I found incredibly useful for puzzles of the type "which direction will it move" (like a spool with a thread pulled at an angle, or a bike with someone on the ground pushing its pedal, or with "faster than wind" sailing cars, etc.) However complex it is, the stuff when acted upon will change its motion so as to accommodate your efforts (the thread of spool should be pulled towards your pull, not pull you hand out; the bikes movement should let your push on the pedal succeed, not push you with the pedal instead; the car will, given no friction, speed up as long as it makes the blades planes move less relative to the air; etc)

[@juanpablomartinez1671]

I've just met your channel and it's terrifically awesome. The way which you explain is superb, the focus of the content it's original and very sharp. I really like it. Thank you so much!

[@PhysicswithElliot]

Thank you so much Juan!

[@lucksterduck]

Such a wonderful video. Thank you!

[@channelsixtysix066]

Just found this channel and subscribed. I have subscribed to several maths channels and I'd like to subscribe to more physics channels. Great presentation, Elliot, thank you.

[@mohammedal-haddad2652]

This is exacly the introductory classical mechanics lectures that I always wanted to find to develope the necessary background to learn quantum mechanics. Thank you very much.

[@adamfattal468]

Tekram

[@robertcantwell9569]

Exceptional presentation , thank you for ur time and effort .

[@whilewecan]

Thank you!!! This is the first time I encountered with such perspective. Revelation. Impressive.

[@hubertorhant8884]

spoken on a soft tone and calmness takes away the "anxiety" brought by the differential equation so that one can focus on the subject at matter ! i've seen this potential graphing many times but any of my teachers dared to emphasize the R_min and R_max meaning and the impact on the orbit ! Just brilliant ! makes me wanna go back to U again. Awesome Elliot ;-)

[@longyang8964]

You are the best among youtuber for physics stuff! Watching your videos is a joy!

[@joselemgruber8098]

Very good !! Thanks for all !

[@esquire9445]

This was awesome, seriously gifted teacher. Wow.

[@RahulSingh-ry9ht]

Found you yesterday, amazing stuff...!

[@JoseAntonio-ml8yg]

Your videos are extremely helpfull. Thanks a lot!

[@aleksandr_berdnikov]

I also like how the effective potential (or ang.momentum & energy invariants) make easy work of geodesics on surfaces of revolution building nice intuition for their features

[@jjzh]

Hey Elliot, your channel is one of the best physics related channels I've ever come across: very simple and simultaneously esthetically beautiful design, with insightful information, props for the great work. I'm currently taking a course on quantum mechanics and I loved the way how you linked Poisson brackets with the commutators and it really helped my deepen my understanding of the subject. I'd love to see some more videos on quantum mechanics that help us develop an intuition for the way it works (e.g. quantum tunneling etc.)

[@PhysicswithElliot]

Thanks JK! More quantum mechanics videos to come!

[@flix7280]

your channel is freaking awesome prof!

[@PhysicswithElliot]

Thanks Ayush!

[@3koningen]

Thank you. You really help!

[@mionio1977]

Great job !!! Keep on !!!

[@wisnuape]

Great content packed with deep physical insight. Now i learn much more about potential energy. Thanks !

[@PhysicswithElliot]

Thanks Wisnu!

[@Noah_Krakatoa]

Great video! For some reason, I like thinking of elliptical orbits sort of like a juggler throwing balls up in the air, where the aphelion would be at the top of the page and the star and perihelion would be at the bottom. So instead of a planet going round and round it’s going up and under

[@ib2415]

Very illuminating

[@charleshudson5330]

Excellent video. Wonderful channel. You have the most perfect baritone for narration. Silky smooth; smoothly reassuring. A tone that can be trusted. (A young Morgan Freeman.)

[@PhysicswithElliot]

Ha! Thanks Charles!

[@robertdavie1221]

Great explanation!

[@david50665]

even all the notes in the link!!!...wow this guy is really on top of it...

[@ravikantpatil3398]

Great explained thanx

[@federicopinto9353]

This is great!

[@declanwk1]

very interesting and enlightening

[@PeterPan-td9qt]

KZbin recommended your channel and I am amazed by the explanation, thanks buddy.

[@PhysicswithElliot]

Glad I could help!

[@MrPoornakumar]

Thank you, very much.

[@jackflash8756]

Really excellent video.

[@AndrewPa]

iMPRESSIVE - as professional in subject would like to say good job mate!

[@albertdowson5436]

Thank you so much bro , the explanation was awesome , really enjoyed the entire video

[@PhysicswithElliot]

Thanks Albert!

[@masganteng1987]

genius. thanks very much

[@leonardopavan2013]

Man, you're just amazing. I'm your biggest fan from Brazil!!

[@PhysicswithElliot]

Thanks Leonardo!

[@kammuller6620]

I really enjoyed the video. It was fun and very relaxing to watch. I will recommend it to my students.

[@PhysicswithElliot]

Thanks Kam!

[@JeanDAVID]

This new concept of the effective potential energy is astonishing to describe the motion of a celestial body around another massive one !

[@Jello1963]

Could you explain Lagrange points as well with potential energy?

[@chrisr9320]

great content!

[@MrShenCat]

Does this trick come from any papers ? It's intuitive. I wonder if their conjugate variables (ie moment vs time diagram) have similar patterns.

[@mesbahalsarraj399]

Great channel! Keep it up. Excellent audio and video quality. Which camera do you use BTW?

[@PhysicswithElliot]

iPhone!

[@ElFazo]

very cool thanks

[@wavvyair]

Awesome video

[@brendanward2991]

20:00 - the graph seems to imply that the orbital speed is at a maximum not at perihelion but just before and just after perihelion, when U(eff) is at a minimum.

[@PhysicswithElliot]

The potential energy goes like -1/r, so it gets more and more negative as r gets smaller. Then since the total energy K + U is a constant, you make the kinetic energy biggest by making r as small as it can go. Remember that the effective potential isn't just the gravitational potential -1/r, but also includes the L^2/r^2 term that came from the angular kinetic energy of the full 2d problem

[@kushagrasinha4828]

Thank you 💗💗💗💗😊 brother I understood everything ❤️🔥❤️

[@neillinneball]

Outstanding!the best I have ever seen. Keep up these great explanations.

[@ilteriskagan7305]

How and where do you do these type of simulations. Please explain. Can we do it too?

[@sergiolucas38]

great video, thanks :)

[@PhysicswithElliot]

Thanks Sergio!

[@atticusfinch3991]

Thanks

[@tomctutor]

Very good Elliot! I feel it prudent to outline some terminology that often confuses students.. The Field is (by definition) _= - the gradient of the Potential_ . *g= - ∇V.* here g is not energy it is a specific force. Ex. it may be the electrostatic force per unit charge at a point [N/C in S.I units]. The potential V is also not an energy (it is the specific potential energy). In our electrostatics example V would be U/Q [J/C or volt]. Consider gravitation, g = Force per unit mass [N/Kg] which of course is simply acceleration from F=ma. The Gravitational Potential Energy at that point would be U= Vm. I hope that clears up any confusion about what is meant by scalar potentials and vector fields versus Potential Energy. ☺ ← ◎

[@eulersfollower7140]

Hey I have a question if you don't mind .In the case of circular orbit ,even if the Kinetic Energy is zero ,it moves because it has angular velocity & angular momentum if I am not mistaken ,in the case of elliptical orbits it has some Kinetic energy (ie) it's not zero except at r_min & r_max .How does that translational Kinetic Energy play in the context of elliptical orbits ? A great video ,please consider making courses on various topics .

[@PhysicswithElliot]

The kinetic energy has a radial piece and an angular piece. It's never zero because the planet always at least has an angular velocity. The effective potential, meanwhile, is a trick that lets us use angular momentum conservation to group the angular kinetic energy term together with the ordinary potential energy for the purposes of analyzing the motion

[@eulersfollower7140]

@@PhysicswithElliot I am still having a problem considering the effective potential in the diagram instead of ordinary potential ,i don't understand how they are equivalent ,could you explain this part ? Thank you ,have a nice day.

[@sciencedon3993]

wonderful

[@TIO540S1]

Might I suggest a video on another topic that yields qualitative and, in some cases, quantitative information about a system without solving the differential equations of motion. That is dimensional analysis and the Buckingham Pi Theorem.

[@PhysicswithElliot]

Will definitely make a dimensional analysis video before too long!

[@abhisheknath5723]

I know your channel is going to grow a lot... I am glad to be one of the early one (well not so early)

[@PhysicswithElliot]

Thanks Abhishek!

[@katnisseverdeen5466]

I'm 16 and in my first year of A-levels. This all seems fascinating and well-explained, but just slightly out of reach with the schooling I have. Can anyone recommend any resources just one step below this? Thanks!

[@amarnathck574]

Question, someone help. If effective potential at r min and r max are the same, and E is constant, then doesn’t that mean that KE is also the same at r min and r max since KE= E-p(eff)??

[@aibisxLife]

Nice💫

[@bowlampar]

Somehow both Physics and Drawing are not simple subjects, they can hardly ' short cut 'to become 'simple' . Student still need to do his homework and read up regularly.😁

[@finaltheorygames1781]

I liked the picture of the potential energy and the orbit of the planet, its shows a whole other perspective.

[@sibilakshman9575]

The derivative of Veff , if 0 would imply that the orbit is circular , can you explain why?

[@kanshokmituithung2782]

May you live long!

[@MarcoAGJ]

Interesting.

[@whatitmeans]

Under which assumptions the relation dU/dt=F stands?... Could you made a video showing how it will be applyied for the nonlinear damped pendulum? Or energy losses will crash the method?

[@PhysicswithElliot]

You mean F = dp/dt? Or -dU/dx?

[@tomctutor]

Force is indeed F= dp/dt in any context. This is another definition just stating that 1 [N] is equivalent to 1 [kgm/s^2] in SI units.

[@ninja-nd1wm]

Uh sir can you please tell me about the PARABOLA case ? That's what I am usually confused about What is the difference between the hyperbola and the parabola orbits?

[@jukukalle100]

I know it’s an older video, but just wanted to let you know that the potential energy U for pendulum in the 2nd example is wrong. You took L cos θ as the height component, when actually it should be L - L cosθ = L (1 - cos θ). so U = mgL(1 - cosθ). The graph is also wrong because of it. At θ = 0 potential energy U has to be 0 for a pendulum. Your graph crosses U axis at -mgL but it should be at 0. Though the following qualitative analysis isn’t affected by this error Otherwise thank you for the great video!

[@keppa3635]

Hey buddy can u plz make a video on writing a lagrange for two block spring system on frictionless surface plzzz...

[@PhysicswithElliot]

Set up your coordinates, write down the kinetic energy of each block, and write the potential energy stored in the spring. Then take the difference and you're home free!

[@bangbang1108]

wow your channel is fukin top g. really incredible

[@charlesbromberick4247]

I thought uou were going to mention CONSERVATION OF ENERGY or ENERGY CONSIDERATIONS, like George Jaun of Cal Tech would do.

[@davidbrisbane7206]

_The motion of the Earth around a star like the Sun_ ... as if the Earth could orbit any other star 😂🤣.

[@dcode1000]

More please. And just a suggestion: if could focus more on visually explaining physics concepts using high quality animation visuals like bluebrown that would make the videos even 10x better.

[@tomctutor]

And probably 10X work for poor Eliot, I like his coloured pen sketches, cheap and chearful and leave 3B1B for the sexy animations. ✎

[@user-cm6hv6tw4m]

at 11.54 u really start to find the purpose of watching this video

[@jaysmith12]

I don't think your wavefunction at 7:50 is correct but I hate to ruin the video. We are measuring phase space of a simple pendulum and separatix math within hamiltonian mechanics reflects the real function of this operation. Making full cyclical rotations is a wave function of pi radians along a periodic timeline. Surely a pendulum makes a spiral function around the stable point.

[@bscutajar]

14:21 is wrong, it depicts the force of gravity to be outwards due to the negative sign

[@davidbrisbane7206]

The only tool you need is Wolfram Alpha 😀.

[@SSNewberry]

use the Lagrangian

[@tomctutor]

Lagrangian (E-U) is equivalent to classical mechanics (E+U) so no need

[@grantofat6438]

The sad thing is that it is not simple to draw a picture. Most people can't do that.

[@schmetterling4477]

That's why you just have to keep at it. You will get better in time and the images in your mind and on the white boards will help you to deepen your understanding quickly. Physics is an extremely visual science. Physicists scribble and draw stuff all day long. It really helps. Don't be shy about it.

[@davidrandell2224]

Galilean relative motion has the earth approaching the released object. D=1/2 at^2 main part of proper equation. The earth is expanding at 16 feet per second per second constant acceleration: gravity. “The Final Theory: Rethinking Our Scientific Legacy “, Mark McCutcheon.

[@wdobni]

these are fun little math games if your mind runs in a mathematical direction....clearly you have a friendly familiar conversational aquaintance with mathematics.....so smoke em if you got em....but i fail to see the point of anybody studying introductory or undergraduate physics - they will never be doing any CERN research or designing any xray machines or hydrogen bombs if one is going to become a professional engineer then this stuff has relevance.....but for most university students learning an FFT and how to apply the newtonian or the lagrangian will be about as useful in later life as chinese poetry or gender theory i don't think there is any useful 'trick' to learning physics and calculus, most of it comes from repetition and problem solving exercises, and eventually the more gifted develop what you are calling an 'intuition' but its actually a familiarity gained by exposure....a concert pianist does not develop a trick or intuition about Mozart, he/she gets there by the method of 8000 hours of practise the same is true for physics and the maths, they are not intuitive disciplines, any moreso than russian is an intuitive language or organic chemistry is an intuitive approach to benzene based aromatic hydrocarbons...its all labor, repetition, and practise.....viewed through the retrospectoscope 10 years later the cancer surgeon might remark that most cancer surgery is 'intuitive' but that is only because he/she eats. sleeps, talks, dreams, and reads only cancer surgery.

[@tomctutor]

All that said, reminds me of the story about Einstein whom failed his maths class miserably in Junior school, his schoolmaster stated on his report; "Young Albert wont amount to anything academically and recommend he takes up some hand skill instead". Mastering maths at this level takes a lot of work and study so don't give up if you are really interested in the subject.✍

[@davidbrisbane7206]

Wow ... but gravity is not a force 😂🤣😂😂🤣

[@vg6761]

Let's be honest. We're never gonna understand this shit. Don't even waste your time. 😅

[@orglancs]

To someone like me, whose love of science was destroyed by school teachers, this is sheer click-bait. I was lost by 2:50 and stopped the video. The trick, if there is one, is invisible and you'll have to be a lot more understanding of people like me (and there are lots of us) if you want to make physics accessible to us. Anything with an equation in it has had it as far as I am concerned. How do I know you are not cheating, shunting your symbols round like chessmen on a board instead of real things? What would your equations look like, if you actually replaced your symbols by real numbers? Would they add up? There's no way of knowing, is there, because you keep everything concealed behind abstract symbols.

[@98danielray]

what the fuck are you even trying to say? of course the equations work if you replace things. thats how equations work

[@vg6761]

Ikr fuck western 'physics'

[@tomctutor]

Dear friend.... You cant have physics without maths, same as you cant have fish without chips. Nature, although elusive in most of its behavior, reveals itself sometimes in symmetry and beautiful logic. Maths is the language in which we interpret and analyze its form. Just like English is how you enjoy a Shakespearian play. Whatever way you crack it open, you need the power and formalism of maths to fully understand it. Any equation in physics is an expression of some "physical law" as Finemann would often state. E.g. force is proportional to acceleration and the amount of matter in a body, so F=ma a.k.a. Newtons' Law of Motion. I think you misunderstand maths equations and their application in our world. The symbolic sophestry is unfortunately necessary so go learn.

[@sadececns00]

Awesome!!!

[@abdirazaqali8921]

Please share us your email. You are great physicist.