[Sidefx-houdini-list] Gravity in Pop

Drew Whitehouse drew.whitehouse at gmail.com
Sat Aug 22 23:15:09 EDT 2009


Well to pick nits, Wikipedia defines "gravity" as a force, the acceleration
is the F/m and happens to be ~ 9.8 ms^-2 near the earth's surface. You could
say that gravititational forces *cause* a mass to accelerate.

-Drew

On Sun, Aug 23, 2009 at 9:38 AM, chris exarhos <
cexarhos at realimaginations.com> wrote:

> actually...gravity is an acceleration, its a change in a constant
> speed(velocity)
>
> -chris
>
> -----Original Message-----
> From: sidefx-houdini-list-bounces at sidefx.com
> [mailto:sidefx-houdini-list-bounces at sidefx.com]On Behalf Of Andy
> Nicholas
> Sent: Saturday, August 22, 2009 7:34 PM
> To: sidefx-houdini-list at sidefx.com
> Cc: sidefx-houdini-list at sidefx.com
> Subject: Re: [Sidefx-houdini-list] Gravity in Pop
>
>
>
> I wouldn't describe gravity as an acceleration. Gravity is a force like
> any other, except that it's magnitude is proportional to the mass of the
> object it's acting on.
>
> F = G M m / r^2
>
> Assuming M is constant (the Earth's mass), then since F=ma, the mass m
> cancels from both sides giving the property of constant acceleration
> independent of mass.
>
> So, the short answer is yes, you're right, the shelf is wrong.
>
> I tend to use "Override Mass" and set it to 1 though, as it's a bit
> ambiguous what it does by ignoring mass. I'm guess it's doing that when
> you ignore mass, but I like to be sure.
>
>
>
>
>
> > Hi, a silly one :)
> >
> > Do I understand it properly? A force in real world react differently
> > depending of the mass but since gravity is an acceleration, no matter
> > the mass all objects should fall at the same speed. For that reason we
> > must check "Ignore Mass" on a Force Pop to simulate gravity but when you
> > create it through the shelf it is not checked by default. Who's wrong?
> >
> > François
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> >
>
>
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-- 
Drew Whitehouse
ANU Supercomputer Facility Vizlab



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