Date: Thu Oct 29 21:58:30 2009 ** **Back to Contents ** ------------------------------------------------------------------------ **

Author: Anthony Lapinski

Subject: Re: centripetal acceleration and friction demonstration


This is a great demo! I use a lazy susan, which you can get cheaply at
IKEA and other places. You can do the same masses (coins, washers) at
different radii, or different masses at the same radius. Rotate the
platform. Compare angular speed and linear speed. Then centripetal
acceleration and centripetal force. Static friction, etc. Relate this to
the Earth spinning, centripetal acceleration, apparent weight (equator vs
poles), etc. writes:
> of moment...right. Yeah, I think stacking a few pennies
>and gluing together might do the trick.
>I'm starting to think this might be a demo that really isn't done all
>that often.
>On Thu, Oct 29, 2009 at 6:29 PM, Bernard Cleyet
> wrote:
>> I'll leap in where others have refused to tread -- I think you've got
>> having the moments at the same radii is most important.
>> bc not an angel
>> p.s. Note: The centre of mass is not the same as the center of moment.
>> Would using varying numbers of same coins stacked (glued together)
>> this?
>> On 2009, Oct 29, , at 15:23, Andrew Morrison wrote:
>>> I wanted to do a demonstration in class where two objects of different
>>> mass are placed on a rotating disk at the same radius to show whether
>>> one will fall off before the other or if they fall off at the same
>>> time.
>>> After multiple trials, first with a dime and a quarter then with other
>>> various objects, I am pretty sure I can convince my class that any of
>>> the three possibilities is correct. Does anyone have a method or
>>> suggestions of techniques for consistent and accurate ways of
>>> repeating this demonstration?
>>> It seems to me that the two objects would need to have the same
>>> material in contact with the surface, to have the same coefficient of
>>> friction, and would need to have the same dimensions, so the center of
>>> mass of each is in the same spot. Is that right, or am I overthinking
>>> this demo?
>>> Thanks!
>>> Andrew

From Thu Oct 29 21:58:30 2009