[SEL] OT: Physics Help & error correction

[John Neth]

Good point, that's the part I forgot. 0 velocity but 9.81 m/s/s acceleration.  Still conceptional.  Knew if I was in error someone would correct me.
The change in direction maintains acceleration with 0 velocity.

John 

Sent from my iPhone

On Apr 11, 2011, at 12:34 PM, Arnie Fero <fero_ah at city-net.com> wrote:

> John,
> 
> I disagree.  The acceleration is the second derivitive of position.
> In the case of your bullet example (ignoring air drag), at the time the bullet
> changes direction from up to down, its velocity is zero, but the accelleration is
> still g (32.17 ft/sec sq or 9.81 m/sec. sq.) as a vector pointing toward the center
> of the earth).
> 
> Arnie
> 
> On Mon, April 11, 2011 11:54 am, John Neth wrote:
>> Constant velocity has no acceleration.  Acceleration is a change in velocity or
>> direction.  The instant a bullet fired vertically changes direction from up to down
>> it has 0 m/s/s acceleration and that is different than 0 acceleration.  Points out
>> the conceptual aspect of physics.
>> 
>> John
>> 
>> Sent from my iPhone
>> 
>> On Apr 11, 2011, at 9:39 AM, Arnie Fero <fero_ah at city-net.com> wrote:
>> 
>>> John,
>>> That's easy.  When you're moving at constant velocity, your acceleration is zero.
>>> 
>>> On Sun, April 10, 2011 6:46 pm, John Neth wrote:
>>>> You are showing your age and a problem with US science.  Newtons and m/s/s.
>>>> 
>>>> In physics there is the math and the conceptual of what is happening.  Concept.
>>>> How do you have an acceleration of 0 m/s/s.?
> 
> 
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