Re: Favorite Test Questions

[Tim Folkerts <Tim.Folkerts@valpo.edu>]

OK,  I'll admit that my knowledge of drag racing, specifically the 
spinning of the tires, was based more on neighborhood kids with 
screeching tires than on competitive racing.

I asked an expert (i.e. someone with a webpage on drag racing), and 
found that BEFORE the race, they spin the wheels out from the starting 
line to
1) warm up the tires to make them stickier
2) put some fresh rubber on the track so that it is a rubber to rubber 
friction, not rubber to pavement,
3) to clean off any grass, dirt, etc from the tires.

DURING the actual race, the goal (not often achieved) is to just avoid 
spinning the tires.  Then the STATIC coefficient of friction is used, 
instead of the lower KINETIC coefficient of friction.


The point of the question (which is somewhat lost now) is that the 
model of friction that we present is a very crude approximation and 
shouldn't be relied on too heavily in the real world.



> There is a huge amount of physics and engineering in auto racing and drag
> racing in particular.  Does anyone know where we can get data (I believe
> it exists, but the owners may not want to share it!) such as acceleration,
> speed, torque, horsepower, down force due to spoiler, etc. as a function
> of time for a highest performing dragster?  I once tried briefly searching
> the web for such info. but came up empty.

Top drag racers achieve 100 mph in 0.8 s, which is an acceleration in 
excess of 5 g!  Even with some downward force from airfoils, that must 
mean that the "coefficient of friction" is nearly 5!

There are web sites with various information on drag racing.  For a 
quarter mile, speeds can be in excess of 300 mph and times under 5 s.  
One site for a drag race track mentioned providing competitors with 
times and speeds at several points along the track.  I bet that 
they would provide most of that info to fans as well.
 



---   Tim Folkerts

P.S.  Now that we have pretty well squashed this question, the original 
request for other favorite questions which test understanding rather 
than memorization of formulas still stands.

********************************************************
Timothy J. Folkerts               Tim.Folkerts@valpo.edu
Dept. of Physics & Astronomy      219-464-6634
Valparaiso University
Valparaiso, IN  46383