Skip to main content
Physics

You are not logged in. Your edit will be placed in a queue until it is peer reviewed.

We welcome edits that make the post easier to understand and more valuable for readers. Because community members review edits, please try to make the post substantially better than how you found it, for example, by fixing grammar or adding additional resources and hyperlinks.

Required fields*

6
  • $\begingroup$ I don't think it's a mistake seeing as the d^2s in question does not represent (dsds) but rather (dds). This comes from dds=d^2s=dds/r=d^2s/r . So more explicitly the canceling out looks like this: α = (dds)v/r(d*s)dt = dsv/rsdt . However, I may be wrong so please do explain if I am. $\endgroup$ Commented Feb 17, 2016 at 9:22
  • $\begingroup$ @H.Turki Aha, I understand, but how can d then cancel out, when d is not a variable? It is just a symbol meaning change in the ds variable. $\endgroup$ Commented Feb 17, 2016 at 9:26
  • $\begingroup$ I was under the impression that d can cancel out as long as it pertains to the same variable (in this case s) - also in my edited comment I mistakenly wrote dds=d^2s=... when I meant ddθ=d^2θ=... my apologies $\endgroup$ Commented Feb 17, 2016 at 9:29
  • $\begingroup$ Remember that ds is a small change. That is the name we have given to a small change in s. If a change in distance s equals the change in some other distsnce x, then we can say ds=dx. But that doesn't mean that s=x. If this was the case, then v=ds/dt would equal v=s/t, which is not at all the case (the later is rather the average speed over the entire distance s and not the instantaneous speed, which the former is). d's don't cancel out since they are not variables $\endgroup$ Commented Feb 17, 2016 at 9:34
  • $\begingroup$ Ok I see your point :) But now instead of canceling if we replace ds with x (representing a small change in s) we end up with α = dxv/rxdt , and then isn't dx/dt approximately v? or is this a different v as ds/dt is not approximately equal to d(ds)/dt? $\endgroup$ Commented Feb 17, 2016 at 9:58