Is Newton's Second Law Valid in an Accelerating Reference Frame?

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Homework Statement


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.


Homework Equations


f=ma


The Attempt at a Solution


i don't 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
 
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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.
 
To solve this, I first used the units to work out that a= m* a/m, i.e. t=z/λ. This would allow you to determine the time duration within an interval section by section and then add this to the previous ones to obtain the age of the respective layer. However, this would require a constant thickness per year for each interval. However, since this is most likely not the case, my next consideration was that the age must be the integral of a 1/λ(z) function, which I cannot model.
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