Re: positive and negative work

[Brian Whatcott <inet@INTELLISYS.NET>]

At 09:11 AM 11/11/01 -0800, you wrote:
> On Sun, 11 Nov 2001, Brian Whatcott wrote:
>
> > Hmmmm...we agree that a car would accelerate down an incline,
> > if a force acting 'uphill' were not holding its speed steady.
> >     We see that this retarding force varies with the throttle so we are
> > confident that the car is supplying this retarding force.
>
> So the car exerts a force on itself?

/snip/

> John Mallinckrodt      mailto:ajm@csupomona.edu
> Cal Poly Pomona          http://www.csupomona.edu/~ajm


Yes: the car (mass) experiences a force on itself which tends to accelerate
it down hill.
(Gravity)
Yes, the car engine exerts a force which can resist this tendency to accelerate
 down hill.

I identified the site of operation as the torque converter, in a case of
interest.

There does seem to be a real interest in how the work done by the drive shaft
on the torque converter is reflected by the tire road interaction.
I'm not sure I heard an explicit answer yet   :-)

John Denker's response is at least clear-cut.
 There is an energy loss from the car's descent.
   There is work done at the torque converter
from two sources: engine and the car's potential energy loss.
But you can't necessarily track it between road descent - tires turning -
drive shaft turning torque converter resistance - converter fluid getting hot.

Is this all we can say - or do we need to define work in one of  John M's
seven ways in order to talk cogently about energy and work in this case?



Brian Whatcott
  Altus OK                      Eureka!