Relevant Interactions
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- All and
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None 
The One strange thing about the One-Dimensional Motion with Constant Velocity - Zero Net Force model is that it is only applicable in the absence of interaction. Thus, in one sense all interactions are relevant to the model, because the presence of any interaction destroys its validity! In another sense, no interactions are relevant, because the model can only be used when you have assured yourself that any interactions acting on the system are either negligible or are perfectly balanced by opposing interactions so that they cancel outapplies when there is zero net force on an object. This does not mean there are no forces or interactions present - it means that if any interaction acts on the system it either produces a negligible force or its force is perfectly balanced by forces from opposing interactions. Thus, there are no interactions present in that are particularly relevant for the Law of Change for this model.