Re: Pushing a car uphill

[brian whatcott <inet@INTELLISYS.NET>]

Sad to tell, many cars have disk brakes that do not
fully retract off the disk surface - these tend to rely on flexure
of the disk brake piston seals to haul them back.
The brake pad itself is not positively attached or retracted
in those cases.

It's the usual static/kinetic friction coefficient issue,
which you can demonstrate by applying light brake pressure while
inching forwards - you can often produce a creek or groan
from the brakes.

Brian W

At 11:14 10/25/01 -0400, you wrote:
> On Thu, 25 Oct 2001 08:18:52 -0400 Wolfgang Rueckner
> <rueckner@FAS.HARVARD.EDU> writes:
> > Kinetic friction is not involved here -- the car is not skidding and
> > neither are the ball bearings in the wheels.  Wolfgang
>
> It has been our experience that it is more difficult to
> start pushing a stalled car on a level surface than it is
> to keep it rolling once the car has started moving.
> Why is this true??
>
> Herb

brian whatcott <inet@intellisys.net>  Altus OK
                Eureka!