Re: Kinematics of Throwing Balls

[Hugh Haskell <hhaskell@MINDSPRING.COM>]

At 15:33 -0400 9/11/02, Ludwik Kowalski wrote:
> Here is a problem to help them memorize the situation.
> A rifle is fired vertically down from a tall building. The
> bullet, initially at rest,  leaves the barrel with the velocity
> of 300 m/s. The distance traveled inside the barrel is one
> meter.
>
> a) How large is the average acceleration inside the barrel?
> b) How large is the acceleration outside the barrel (ignore
>     air resistance).
>
> They must know that "free fall" is a situation in which
> weight is the only acting force.
>
> Later (when Fnet=m*a is known) you can add the third
> question. Giving the bullet's mass (say 10 grams) ask:
>
> c) How large would the acceleration be in water if the
>     water resistance force were 100 N?
I would just like to point out that if we don't talk about
acceleration until after the concept of force is introduced, then
questions like the one Tina has raised seldom even come up.

Maybe the reason it took nearly nineteen hundred years to break the
Aroistotelian mold is that history doesn't operate in a logical
sequence.

Hugh
--

Hugh Haskell
<mailto:haskell@ncssm.edu>
<mailto:hhaskell@mindspring.com>

(919) 467-7610

Let's face it. People use a Mac because they want to, Windows because they
have to..
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