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Principle of newtonian relativity

  1. Sep 2, 2008 #1
    1. The problem statement, all variables and given/known data
    In a lab frame of reference, an observer finds Newtons second law is valid in the form of Fnet=ma. Show that Newtons second law is not valid in a reference frame moving past the laboratory frame of problem 1 with a constant acceleration a1. assume that mass is an invariant quantity and is constant in time.

    2. Relevant equations

    3. The attempt at a solution
    i dont get how to show this, i get how to show that the velocities and displacement would be different but not how to relate that to the force
  2. jcsd
  3. Sep 7, 2008 #2
    Suppose instead that we wish to show that NSL is valid in a 2nd frame moving at constant speed b. The Galilean (sp?) transformation is

    x' = x - bt

    where the primed quantities are in the moving frame, and b is some constant speed. If we differentiate this twice with repsect to time, we obtain

    a' = a

    Since mass is invariant, F = ma holds in both frames.

    Now do the same thing, but assume that b = a1 t, also the speed of the moving frame but written in terms of a constant acceleration a1 and time. You should find that acceleration is this case is not invariant.
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