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  • I get the confusion, but a reference frame is a very important limitation for calculating what you need. Its not about whether the arm exists behind the hand, but whether its effects are important for the calculation.

    For the sake of the hand pushing the ball, its not. Only the momentum of the hand and the inertia of the ball are important.


  • Derpenheim@lemmy.ziptoAsklemmy@lemmy.mlIs every action a reaction?
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    16 hours ago

    That strongly depends on your reference frame. As in, what system are you looking at? Where are you drawing your box? If your box is around the entire universe, then yes, every action is a reaction stemming from the big bang, with very few notable exceptions pertaining to black holes that I wont go into.

    However, if your reference frame is a hand and a ball, then the hand pushing the ball is an original action, the ball moving its reaction.