Re: Gun barrel

["Villa . Zosimo Oscar P. Jr." <ocavilla@pusit.admu.edu.ph>]

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|    Zosimo Oscar P. Villa Jr.		       (@-@)  
|    Physics Teacher			     _<----->_			 |
|    Science Department			    ( (     ) )			 |
|    Ateneo de Manila High School	     \ \m m/ /			 |
|    email : ocavilla@pusit.admu.edu.ph	     ^^^   ^^^			 |
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On Tue, 26 Nov 1996, Dwight Souder wrote:

>         Greetings everyone!  Lately, we've been going over projectile motion
> in my high school physics classes.  One of my students asked me a question
> pertaining to both rifles and potato guns.  Does the length of the barrel of
> the gun help determine the velocity of the projectile?
>         I'm not a hunter or shooting enthusiast, but I have fired some guns in
> the past.  I'm actually ignorant as to the makings and purposes of the various
> parts of a gun.  I know in the barrel of the gun it is usually spirraled to
> help induce a spin on the bullet to help keep the bullet from tumbling.  Can
> the length of the barrel actually help increase or decrease the velocity of
> the projectile once it leaves the barrel?  In other words, if I have two
> identical bullets, but one is fired from a gun with a long barrel and the
> other with a short barrel, will there be any difference?
>         Any help would be greatly appreciated.
>
> Thanks,
> Dwight
> Ashland, OH
In a variation of Newton's second law in equation form (F=ma) is an
equivalent equation Ft=m(deltav). That is the impulse delivered to an
object is equal to its change in momentum. (Another way of saying, that a
net force is required to accelerate an object)

> From a textbook discussion (i forget which) given two guns with the same
bullets, the one with the longer barrel exerts a force over a longer
period of time on its bullet because it stays in its barrel for a longer
period of time. That means that in the equation, t is greater for the
longer barreled gun. since both bullets ahve the same mass, and both start
from rest, the speed of the bullet from the longer barrel is greater than
the bullet from the shorter barrel.

I think the fact that the the bullet experiences a significant amount of
force pushing it out because of the explosion ("expanding" gas inside the
gun).

Is this too simplistic?

Any gun enthusiasts among you?