Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: steering



Thanks, Brian, for correcting a typing error in the name
of the thread. You wrote:

This seems like an awful lot of hand-wringing about
turning a car. I am happy to visualize the steered
wheels (and the driven wheels too) providing a brute
force sideward push, at the cost of scrubbing more
or less rubber off the tread. I find no need for
minimization model. Am I missing something?

The "awful hand-wringing" is part of what we do. We
try to account for what happens in terms of what we
have already accepted. I suppose I am still allowed
to say that an explanation is a process of establishing
a cause-and-effect line of reasoning. Fortunately, as
I read somewhere, "we do not have to understand
digestion to enjoy good food."

Let me follow your "scrubbing the rubber" idea. A
chilld is on a tricycle with legs in the air. The front
wheel is forced to reorient itself (by an internal
torque from the child). The wheels are not powered.
The front wheel starts rubbing the road. It acts on
the road and the road starts acting on it. A new
external force from the road appears; I must daw an
arrow for it in my free-body force diagram. That
force would produce linear acceleration (slowing
down the center of mass). But it produces centripetal
acceleration instead; the center of mass keeps
turning at an essentially constant speed. How can
this be explained? Except for tires all three wheels,
and balls in their bearings, are perfectly rigid.
Ludwik Kowalski