Thanks Kees for the detailed explanation. It is cristal clear now. I have commited the patch[1] to upstream.
Thanks a lot. Jordi, [1] http://git.gnome.org/browse/gbrainy/commit/?id=ed383851c7d83f2d3c7952a399e615aa1d3c74b1 El dv 21 de 01 de 2011 a les 11:30 -0800, en/na Kees Cook va escriure: > Hi Jordi, > > On Fri, Jan 21, 2011 at 07:16:57PM +0100, Jordi Mas wrote: > > I think that your fixes the issue partially. > > > > The screen capture at the left shows the first formula and at the right > > the second one. > > > > The screen capture at the right looks wrong to me. > > > > Please correct me if I'm wrong. > > Both screen captures are correct. (Note that distance on the left is > "1" and "2" on the right). > > M = Fd (http://en.wikipedia.org/wiki/Lever) > > M = torque (or turning force) > F = downward force (for the simple case "weight", the mass * gravitational > acceleration) > d = distance from fulcrum > > i.e.: torque = weight * distance > > On the left screen capture: > Left: 12 weight * 4 distance = 48 torque. > Right: X weight * 2 distance = 48 torque > X weight = (48 torque / 2 distance) * (weight * distance / torque) > X weight = (48 torque * weight * distance) / (2 distance * torque) > X weight = 48 weight / 2 > X weight = 24 weight > X = 24 > > On the right screen capture: > Left: 12 weight * 4 distance = 48 torque. > Right: X weight * 1 distance = 48 torque > X weight = (48 torque / 1 distance) * (weight * distance / torque) > X weight = (48 torque * weight * distance) / (1 distance * torque) > X weight = 48 weight / 1 > X weight = 48 weight > X = 48 > > > I should have used "torque" instead of "force" in my patch to help clarify > the difference between turning force (torque) and downward force (weight). > > -Kees >
