[SEL] OT: Physics Help & error correction

[Arnie Fero]

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.?