Newton's third law says that for every action there's an equal-but-opposite reaction. Hidden inside it is a deep principle of physics: conservation of momentum! Get the notes for free here: https://courses.physicswithelliot.com/notes-sign-up Newton's third law looks a little strange the first time you see it: all forces between particles come in equal-but-opposite pairs. But it's really all about a more intuitive physical principle: the conservation of momentum. It implies that in an isolated system---meaning one where there are no outside forces acting on it---the total momentum will be conserved. I'll explain why in this video. But there's a catch: Newton's third law isn't always true! Get the links here: https://www.physicswithelliot.com/third-law-help-room A more advanced video about Noether's theorem: https://www.youtube.com/watch?v=O0NYaO_OnH4 Tutoring inquiries: https://www.physicswithelliot.com/tutoring 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 https://www.Patreon.com/PhysicsWithElliot, or make a one time contribution at https://www.physicswithelliot.com/support-me. 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 https://www.physicswithelliot.com/.