Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.1 6/24/83; site mmintl.UUCP
Path: utzoo!linus!philabs!pwa-b!mmintl!franka
From: franka@mmintl.UUCP (Frank Adams)
Newsgroups: net.physics
Subject: Re: Friction
Message-ID: <729@mmintl.UUCP>
Date: Thu, 24-Oct-85 13:41:38 EST
Article-I.D.: mmintl.729
Posted: Thu Oct 24 13:41:38 1985
Date-Received: Thu, 31-Oct-85 04:04:08 EST
References: <956@decwrl.UUCP>
Reply-To: franka@mmintl.UUCP (Frank Adams)
Organization: Multimate International, E. Hartford, CT
Lines: 20
Summary: 


[Not food]

In article <956@decwrl.UUCP> shuster@oblio.DEC (ROBERT L. SHUSTER) writes:
>It is very much easier to turn the wheel (using the steering wheel) of 
>a moving car than that of a stationary car.  The surface area of tire 
>on the road does not change as it begins to rotate.  The difference in 
>ease of turning, then, is the difference between friction on 
>stationary object and friction on a moving object.

No, something quite different is happening in the moving car.  The key is
that the tires are not rigid.  When you turn the wheel a little, you create
stress in the tire near the road.  If the car is not moving, turning the
wheel further requires the tire to slip against the road, whence friction
comes into play.  For a moving car, that portion of the tire spins on out
of contact with the road, relieving the stress.  Thus friction plays little
part in the ease of turning the wheel in a moving car (unless it becomes
very low, such as on ice).

Frank Adams                           ihpn4!philabs!pwa-b!mmintl!franka
Multimate International    52 Oakland Ave North    E. Hartford, CT 06108