Re: [Phys-l] Newton and Snell (was Global evolution as fact)

[William Robertson <wrobert9@ix.netcom.com>]

Hi all,

I'm not sure I would dismiss kinematics so readily. There are  
certainly a number of E and M applications of kinematics where one  
doesn't have to worry about air resistance, and there are practical  
applications such as auto accident reconstruction. Plus, 2-D  
kinematics can be a valuable introduction to the general notion of  
orthogonal independence that permeates much of physics. I do agree  
with John that the topic must be addressed in the context of true  
understanding rather than generalized formula plugging, the latter  
being all too common.

Bill




On Jan 12, 2011, at 11:07 AM, LaMontagne, Bob wrote:

> John,
>
> I have no doubts that physics can teach these topics more  
> effectively, especially if there is some hands-on component to the  
> teaching. My question really goes to whether we should be teaching  
> kinematics at all. Most accelerations in practice are not constant.  
> Most projectile motions are not parabolic  (even in the flat earth  
> approximation) because of air resistance. There are many useful  
> topics we choose to leave out of general physics. I just hope we are  
> not spending an inordinate amount of time on idealized motions just  
> to produce practice problems for F=ma. Most motion problems can be  
> done more easily using momentum and energy - and don't require the  
> artificial restriction of constant acceleration - although that  
> class of problems is easily included. Take the case of dropping a  
> ball---most of the interesting parameters of the motion come from  
> energy balance - the kinematic equations aren't actually used at all.
>
> Bob at PC