Re: [Phys-l] circular motion FBD

[Philip Keller <PKeller@holmdelschools.org>]

Have a student walk in front of a motion sensor and you will see that most walking consists of starts and stops or a t least slowings and speedings.  So which way your foot slips depends on when in the stepping cycle you hit that banana.  If it is as your foot lands, your foot will slip forward.  If it is as you step forward, your foot will slip back.

> -----Original Message-----
> From: phys-l-bounces@carnot.physics.buffalo.edu [mailto:phys-l-
> bounces@carnot.physics.buffalo.edu] On Behalf Of Robert Cohen
> Sent: Tuesday, November 01, 2011 9:49 AM
> To: Forum for Physics Educators
> Subject: Re: [Phys-l] circular motion FBD
>
> Getting away from circular motion but...
>
> On 10/31/2011 04:57 PM, Anthony Lapinski wrote:
>
> > Also, doesn't static friction propel cars and bikes (and people
> > walking) forward? If you stop pedalling or stepping on the gas, the
> > moving vehicle will eventually stop.
>
> For people walking, you need static friction directed forwards to
> *start* the motion forward.  While walking, though, I'm guessing
> friction is periodically directed backward and forward as one steps down
> and then pushes off.
>
> What happens when you step on a banana peel (low friction)?  Does your
> foot slip forward (removal of friction pushing backward) or does your
> foot slip backward (removal of friction pushing forward)?  Google
> "slipping on a banana peel" in google images to see what cartoonists
> think.
>
>
> Robert A. Cohen, Department of Physics, East Stroudsburg University
> 570.422.3428   rcohen@esu.edu    http://www.esu.edu/~bbq
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