This is a multi-part message in MIME format. ---------------------- multipart/alternative attachment Professor Fowler's comments make complete sense to me. But I do not = understand some things that your folks state. "If you then push down on one end and let go the see saw will rock back = and forth until slowly it refinds its state of equilibruim." Why would it rock back and forth? I don't think it would. If you push = down on one end, it will continue with the rotational movement you = imparted until either friction stopped it, or until one end hit the = ground perhaps. If, as the professor says, the seesaw has the axle right = through the center of gravity of the plank, it would always be in = equilibrium, and have no need to "seek" some state of equilibrium. "I understand that friction is the thing that brings it back into = equilibruim, ..." It will always be in equilibrium, friction will only serve to slow the = rotational movement. "...but why the rotational movement to begin with exactly?" Because a seesaw is constrained in that manner, only allowing rotational = movement. Or am I missing something here? "Science answer: Gravity applied to the see saw, gravity applied to the = weight, force/counter force etc." I don't think gravity really has much net effect in this situation - = other than to keep things from flying away from us. "Ya think ?? Funny how a phsyics professor seemed to miss this..." Don't understand your thinking here at all. Terry Farrell Brian Lawson wrote: > Science answer: Gravity applied to the see saw, gravity applied to = the > weight, force/counter force etc. Ya think ?? Funny how a phsyics professor seemed to miss this... or did = he. Perhaps you could take a shot at being a bit more specific..... ?? =20 ----- Original Message -----=20 From: "Richard Brekne" <Richard.Brekne@grieg.uib.no> To: "PTG" <pianotech@ptg.org> Sent: Friday, February 28, 2003 2:44 PM Subject: A "simple" see saw question > List... >=20 > In my pursuit of a better understanding of the concept of Balance = Weight and in > general of grand action leverage ran into this seemingly simple = question, and > posed it to several folks around the world. Here is a response I found > particularilly interesting. >=20 > From >=20 > Michael Fowler wrote > Commonwealth Professor > Department of Physics > University of Virginia >=20 > > Richard Brekne asks: >=20 > > >Given a see saw with say 10 kilos weight 1 meter on each side of = the > > >fulcrum. If you then push down on one end and let go the see saw = will > > >rock back and forth until slowly it refinds its state of = equilibruim. > > >Why exactly does this happen ? I understand that friction is the = thing > > >that brings it back into equilibruim, but why the rotational = movement to > > >begin with exactly ? > > > > >Richard Brekne > > > > Perhaps you think I know something about seesaws because of my notes = at > > http://www.phys.virginia.edu/classes/581/RotationalMotion.html > > > > I agree with you that IF a seesaw has the axle right through the = center of > > gravity of the plank, there's no reason why it should go back to a > > horizontal position. But I've seen seesaws in playgrounds where it > > definitely does go back to horizontal -- I believe these must be = built with > > the center of gravity of the plank slightly BELOW the axle, so the = stable > > position is horizontal. I also seem to remember some very fancy = seesaws > > with hydraulic dampers -- obviously, these could be adjusted to keep = the > > rest position horizontal. >=20 > So... either he misunderstood the question... or I've some more head = scratching > to do. :) whatelse is new eh ? >=20 >=20 > -- > Richard Brekne > RPT, N.P.T.F. > UiB, Bergen, Norway > mailto:rbrekne@broadpark.no > http://home.broadpark.no/~rbrekne/ricmain.html >=20 >=20 > _______________________________________________ > pianotech list info: https://www.moypiano.com/resources/#archives ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/70/c5/3f/df/attachment.htm ---------------------- multipart/alternative attachment--
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