Explaining the Principle of Least Action: Physics Mini Lesson

This video is the first part of a series about the principle of least action, explaining the action for a particle in Newtonian mechanics. The second is about a particle in special relativity, the third about a particle in general relativity, and the fourth about the action for a string in string theory.

About physics mini lessons:
In these intermediate-level physics lessons, I'll try to give you a self-contained introduction to some fascinating physics topics. If you're just getting started on your physics journey, you might not understand every single detail in every video---that's totally fine! What I'm really hoping is that you'll be inspired to go off and keep learning more on your own.

About me:

[williamchurcher]

As a mathematician, your content is some of the best I have ever seen. I love getting my teeth into the equations and proofs, and I love seeing stuff like this as well as your introduction to string theory video. Keep it up!

[douglasstrother]

"The Principle of Least Action" ~ The Feynman Lectures, Vol. II, Ch. 19
Richard Feynman inserts a "WOW! That's cool!" lecture in the middle of his electromagnetism lectures. It starts with a personal account of how he was introduced to this idea.
I came across this before getting formally introduced to Lagrangian Mechanics.

[hrperformance]

Thank goodness for all the genius minds that have contributed to this wonderful subject and all the amazing teachers like this guy. I am so excited to get to grips with this and more!!

[LoreProkop]

Thank you so much! This and its companion videos were the clearest and most understandable explanation of the PoLA and world lines, plus special and general relativity that I have watched, and I watched a *lot*! The math was perfect and well chosen, easily followed, well done!

[amritawasthi]

I've always wondered to know things related to physics but what pulled me out to learn was that i was more interested in mathematics without applications aka pure maths. But to be really honest you're a saviour for me in that case. I love the way you explain things. Thank you so much for being there and a very happy new year from my side. More health to you.

[techconbd]

Dr, please make a whole lecture series on Classical Mechanics (all of Lagrangian, variational calculus, Hamiltonians, phase space and all of it)
This is the rarest thing in the whole online universe.
A request from Bangladesh 🖤🇧🇩

[wowtbcmagepvp]

Wonderfully clean. I’ve seen this proof many times — and only this one connects all the dots effortlessly to why we are even doing this in the first place.

[eastofthegreenline]

A nice treatment of this topic. Very much enjoyed it!

[rapp]

Your videos are always very well done. Thank you.

[dankoyg]

Elliot. 🎉. Wonderful! You explain things so clearly. You have a clear mind. You get straight to the point. You are concise. You enunciate with precision. And some of the material I have been exposed to, and did not understand very well, I understand better now. More please …. Thanks so much!

[ssym]

Thank you Elliot!
Your videos are extremely helpful!

[jimwang]

Thanks for your video, they are very logical and simpler to understand, they have make me have another perspective to understand about the mechanics for my freshman year to learn deeper understanding in physics. Thank you!

[michaelshmilovich]

Dr. Elliot -- you're a mensch. Thank you for these very clear and visually intuitive videos. I'm not a physicist or a mathematician (my science background is mostly molecular biology). However, I'm trying to learn modern physics on the side and your vids coupled with Sean Carroll and Lenny Susskind's are VERY helpful.

[jackr]

Great way to tackle this kind of topics, keep it up man

[nillchen]

Thank you, I learned this during my time at Duke but had forgotten about it :) Now it's back, very well explained!

[augustisalman]

Thank you is not enough. ❤ man to man. May he bless you in every good deed you do in every second of it along you life time.

[jfuzukj]

Fantastic lecture. subscribed. Thank you.

[austintumblerock]

Excellent video brother, you just gained a subscriber !

[dukenukem]

Good stuff! I've never heard this account before. I can't wait for the relativistic generalizations!!!

[sourabhjogalekar]

path of least "action"- story of my life