Re: [Phys-l] circular motion FBD

["Robert Cohen" <Robert.Cohen@po-box.esu.edu>]

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