Re: The drag force -- a correction squared

[David Bowman <David_Bowman@GEORGETOWNCOLLEGE.EDU>]

Regarding the comments of Ludwik & Brian concerning Jack's observation:
> Jack should have said that "if everything else is the same"
> (air, shape and size of the object, same planet, etc.) then
> the drag force is proportional to the mass of the object.
> That how I interpreted his comment. But I agree with
> Brian that the statement is not valid in general.

Although Jack certainly needs *no* defense from me, I would point out
that what Jack said was perfectly correct (and clear) as he stated it.
He is quite correct that *at terminal velocity* the drag force is
proportional to the mass.  He *never* claimed that the drag force was
proportional to the mass as a function of velocity.  Rather, only that
*at* the terminal velocity, whatever it happens to be, the drag force
*is* proportional to the object's mass simply because *at* the terminal
velocity the drag force equals the object's weight, and the weight *is*
proportional to the mass where the gravitational field strength is the
proportionality constant.

David Bowman
David_Bowman@georgetowncollege.edu