There a lot of good resources - maybe try these to start: https://www.feynmanlectures.caltech.edu/II_19.html https://www.feynmanlectures.caltech.edu/II_19.html

There a lot of good resources - maybe try these to start: https://www.feynmanlectures.caltech.edu/II_19.html https://www.feynmanlectures.caltech.edu/II_19.html http://www.damtp.cam.ac.uk/user/tong/dynamics/two.pdf http://www.damtp.cam.ac.uk/user/tong/dynamics/two.pdf https://theoreticalminimum.com/courses/classical-mechanics/2011/fall/lecture-3 https://theoreticalminimum.com/courses/classical-mechanics/2...