Re: [Phys-l] Interactive Physics Question

["Zajac, Richard" <rzajac@sal.ksu.edu>]

After you create the force, go into its Properties window.  Under "Active
When", enter something like:
     and(t>10, object[1].v.x <2)

In this example, the force becomes active after 10 seconds, and stays on
until the object reaches a horizontal velocity of 2 m/s.
You can make the force insanely large, and IP will apply it as briefly as
needed to get the speed you want.

RZ

-----Original Message-----
From: phys-l-bounces@carnot.physics.buffalo.edu
[mailto:phys-l-bounces@carnot.physics.buffalo.edu] On Behalf Of John Denker
Sent: Thursday, October 18, 2007 8:51 AM
To: Forum for Physics Educators
Subject: Re: [Phys-l] Interactive Physics Question

On 10/18/2007 09:39 AM, Ron Curtin asked:
> .... how
> to make it begin moving at a constant speed at any time other than the
start
> of the simulation.  Does anyone out there know how to do that?  

Brief, reeeally large acceleration at the appointed time.

Note that a discontinuous change in velocity is unphysical.
Therefore we shouldn't be surprised that it is hard to model.
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