Re: Tire marks on road

[Bob LaMontagne <rlamont@POSTOFFICE.PROVIDENCE.EDU>]

I think the reason that the marks are greater at the beginning is because of available
torque. You get the rpms up to about 4000 before you pop the clutch - which is close
to the top of the maximum torque range for a high performance engine (vs about 2500
for a typical normal performance engine) So you have lots of torque available and burn
rubber. Eventually the the car speeds up to the point where the normal (non-sliding)
rotation rate is associate with high engine rpm. You then quickly have the rpms rise
above the maximum torque range and you can no longer burn the tires - hence the fade
out at the end. You can get a little more burn if you shift up and pop the clutch
again - your are again in the max torque range. It's different physics than the skid
marks from braking.

Bob at PC (who obviously had a mis-spent youth)

John Barrer wrote:

> At the beginning of the skid, the delta v between the
> locked tire and the road is greatest. Thus, I think
> the darkest area is at the start of the skid. Also, if
> you inspect the tire tracks of a car that has "peeled
> out" from a standing start, the tracks are darkest at
> the start of the "peel", not at the end. Again,
> greater delta v seems to be associated with darkness.
> John Barrere
> --- "Fakhruddin, Hasanbhai" <hfakhrud@BSU.EDU> wrote:
> > A tire mark on a road due to hard braking is dark at
> > one end and fade=
> > s
> > out at the other.  Which way was the vehicle moving
> > when the brakes w=
> > ere
> > slammed? =20
> >
> > This morning I wondered when I saw such marks.
> >
> > Hasan Fakhruddin
> > Instructor of Physics
> > The Indiana Academy for Science, Mathematics, and
> > Humanities
> > BSU
> > Muncie, IN 47306
> > E-mail: hfakhrud@bsu.edu
> >
> > This posting is the position of the writer, not that
> > of SUNY-BSC, NAU or the AAPT.
>
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> This posting is the position of the writer, not that of SUNY-BSC, NAU or the AAPT.

This posting is the position of the writer, not that of SUNY-BSC, NAU or the AAPT.