Class content > Newton's Laws > Newton's Laws as Foothold Principles
Prerequisites
Although it is not traditionally specified explicitly as part of Newton's laws, our conceptual idea of object egotism plays a critical role in being able to disentangle complex situations. It says that to understand a situation where objects are interacting with each other, we focus on a particular object. That object knows nothing except what is being done to it at a given instant. It then responds to all those influences (forces) by changing its state of motion or not.
We will specify this formally as a pre-law to the standard set of Newton's laws and set it out as an explicit principle:
Newton's 0th Law: Any object (or part of an object) responds only to the forces that are being exerted on it by other objects and it responds to them at the instant it feels them.
This is explicitly stated in part to help us avoid some "dangerous bends" -- errors that are easy to slip into and not notice that one is making them. Here are a couple of things to watch out for.
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Follow-on
Joe Redish 9/22/11