If you have a perfectly elastic material, the maximum force happens at
the end of the compression, when the spring is completely compressed.
If the material is perfectly inelastic, but still compresses at a
constant rate for a given force, then the force will be constant
during the deceleration. If the spring and the inelastic material
compress at the same rate initially, then the (constant) force of the
inelastic compression will be equal to the force of the spring at some
point early in its compression, which will be less than the force
later in the compression.

Sean


On Mon, Oct 12, 2009 at 1:50 PM, Olin Lathrop <olin_piclist@embedinc.com> w=
rote:
> Sean Breheny wrote:
>> Olin, also don't forget that bouncing causes higher peak force than a
>> simple acceleration to a stop.
>
> No, it doesn't. =A0I'm sure the card bounces some, but it still has to co=
me to
> a stop before reversing direction and going back up. =A0With perfectly el=
astic
> materials, the decelleration and subsequent bouncing accelleration profil=
es
> are symmetric. =A0With real materials, some energy will always be absorbe=
d in
> the compression of the materials during the decelleration phase. =A0This
> energy won't be released during the bounce accelleration phase, making th=
at
> accelleration less than the initial decelleration. =A0After all, the card
> won't bounce to anywhere near the original 10 feet, so obviously a good
> chunk of the energy is absorbed by the material as it initially deforms.
>
> If you think the accelleration due to bounce is higher than the initial
> decelleration to zero, then you have think the material springs back more
> quickly than it got initially compressed. =A0That's not likely, and any
> inelasticity will actually make it go the other way and dissipate energy
> too.
>
> Resonance could lead to higher accellerations, but that has little to do
> with bouncing.
>
>
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