how to calculate acceleration

  Time based animation and gravity
From:         Darrel Plant <>
Subject:      Re: Time based animation and gravity - Help!

At 4:07 PM -0700 8/10/00, Martin Pallett wrote:
1. How do you calculate acceleration in a time based

the basic formula I am using for the linear animation is
   newloc = elapsedTime * vector / overallTime + startloc -- 
thanks to Darrel Plant

but I am stumped when it comes to including the math involved in the

Gravity acceleration is itself a time-based formula, the standard
simple form is:

   accel (t) = 32 ft / (t * t)       (or 9.8m / (t * t) )

That's usually referred to as g.

Acceleration doesn't tell the whole story, though. What's more useful
is the distance travelled in free fall:

  distance (t) = g / 2 * (t * t)

or in feet:

  distance (t) = 16 (t * t)

Pretty simple. You'll probably want to futz around with the value you
multiply t squared by, unless you've got other animations conforming
to real units, this is probably not exactly what you want.

2. Should overallTime include the time taken for any bounces? or should
it be tacked on afterwards as a result of velocity at impact?

Unless you're making a simulator, just do what looks best.

There's lots of pages on the physics of free-falling bodies. Here's one:

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