Re: [Phys-l] real-world problem and other questions about Car Talk

[brian whatcott <betwys1@sbcglobal.net>]

Hmmm....probably better to remember that what ails an old starter motor
 is usually the  copper loaded carbon brushes, which wear away to nubs.

What ails a bad hot starting car is often the carburetor with which these
 rascals were fitted. The problem is fading with cars provided with
computer controlled  multi port injection, now the preferred way.

While touching on car issues again, I suppose I had better resist the
temptation to strongly support the recent  advice to drain the tank
 empty in order to gauge the contents by increments.

 The method is quite credible -but sadly, if this is done in an older car,
it will  often lead to engine problems , and provide a dose of humility
to people who  uncritically accept physicists'  'real-world' solutions.
For light aircraft, carrying a tubular plastic dip stick avoids the need
 to replace  tank transmitters  at $250 on up or gauges at $150 on
up and can be more accurate.
 But light aircraft use tank sump drains and low point drains which are
 sampled before every flight, so that the sediment and water which
 otherwise accumulates over the years in car tanks, is avoided.

Brian W

On 2/5/2011 3:40 AM, Bob Sciamanda wrote:
> ?From Jan 1994 Car Talk:
>
> http://www.cartalk.com/content/columns/Archive/1994/January/03.html
>
> -Bob
>
> -----Original Message-----
> From: Elizabeth Malatin
> Sent: Friday, February 04, 2011 8:59 PM
> To: Forum for Physics Educators
> Subject: Re: [Phys-l] real-world problem and other questions about Car Talk
>
> More on the Car Guys…..
>
> I have been reading the discussion about the gas tank puzzler on Car
> Talk and I started thinking about several Car Talk bits that I would
> like to have as audio files.   These are not particularly funny or
> weird bits, but they were outstanding examples of Tom and Ray applying
> some basic physics to diagnose a car problem.  I think that playing
> these files in class or at least having a link to them on my class
> homepage would help the students value the knowledge that they are
> learning in physics class.  The example that comes to mind is one
> where an electric component in a caller’s car would work when the car
> was first started but then would not work when the car was warmed up.
> Tom and Ray explained that electric resistance increased with
> temperature.  The component was receiving enough current when the car
> was cold, but the increase in resistance due to the increase in
> temperature reduced the current to below the component’s threshold
> operational limit.  Does anyone remember this?  I looked on the Car
> Talk website and they have many years of complete shows but no archive
> of specific problems.  Has anyone saved audio bits of physics/science
> related problems?  I almost want to ask Tom and Ray to do an educator
> CD for the Shameless Commerce Division.  Would anyone else be
> interested?
>
>
> Nikki Malatin
> West Caldwell High School