Hi all Bruce wrote;
At 09:31 PM 12/16/2004 -0600, you wrote:
> There is no force on the nut unless there is force on the lever to crack
>the nut, i.e. a force elsewhere effects the force on the nut, whether the
>hands move or not. I think that is why your example is skewed. Something
>somewhere has to cause that channe in force Eric. This is why I get
>frustrated when someone jumps to kinetics without fully acknowledging that
>kinematics must come into play.
Bruce are you saying that motion causes the force? I agree that kinematics
are intimately related to kinetics. Force causes the motion and not vice
versa. Yes, something has to cause the force, but the force causes the
motion. The force can change without there being motion. Take a see saw
and sit on one side. The force between the underside of your end of the
see saw and the ground is roughly your body weight. Now place something
that weighs a quarter of your body weight on the other end of the see
saw. The force under you end of the see saw is now 3/4 of you body
weight. There was no change in position, but there was a change in force.
> If a force changed from one test to another, w/ and w/o an orthotic,
>then some position of bone, or at a joint or joints changed to alter those
>forces.
Why? Why does there have to be a change in position for there to have been
a change in force?
> And, if the calcaneus or STJ have show no measurable change, for
>example, then something somewhere else that effects teh calcaneus or STJ had
>to have moved or changed position to effect this change in forces.
I still don't see what you mean by my example is skewed.
Cheers,
Eric Fuller
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