Re: The drag force

[brian whatcott <inet@INTELLISYS.NET>]

At 10:32 10/6/00 -0400, Justin Parke wrote:
> In my AP physics class we were recently discussing the drag force
> and how it applies to Newton's second law
> [please no comments on the validity of Newton's law or inertial
> reference frames! :) ].
>
> In any case, an example I pulled [...] had a resistive force
proportional to mv.  The Drag force given by Halliday and Resnick,
 however, does not depend on the mass of the object in question at all.

  My question is:  is the resistive force in the [...] problem an
accurate picture of reality or simply made up to simplify the math?
It doesn't seem reasonable to me that the resistive force would
 depend on the mass...otherwise no one would think that heavy
objects fall faster!
> Justin Parke
> Oakland Mills High School


Well, there you have it, Justin. I expect you read the responses.
You seem to see that in dropping a mass to a terminal velocity it is not
logical to state that drag force is proportional to mass or to velocity,
for the reason that there is a wide range of terminal velocities
 available for any given mass or drag force, and a wide range of
masses for any given terminal velocity or drag force - and the two
components m.v need not form a constant product for constant drag
 force here.

However, we may be the only two who have spoken to this issue.

   I could have wished that you received more focussed, more helpful
 discussions of your question. Perhaps an experimentally oriented
 list would be helpful? Perhaps a different text might be clearer?

Sincerely

Brian

brian whatcott <inet@intellisys.net>  Altus OK
                Eureka!