Bullets, Clay, and Love
Nurtured by Brian Kim, Seth
Sutherland, and Ty Yokoyama
The
aim of this experiment is to find the relationship,
if any, between the distance a shooter stands from a target, and the amount of
force received by the target upon impact. Fundamental concepts of physics
explain that momentum, defined as “a measure of the motion of a body equal to
the product of its mass and velocity” (Giancoli),
can not be created nor destroyed, and that the neutralization of the momentum
of an object must be done through the assimilation of the momentum by another
object. In this experiment, as the bullet travels through the air toward the
target, several forces and objects absorb the bullets momentum before it
reaches the target, such as air friction, drag, and gravity (Trefil). Though the effects of such forces are incredibly minute
due to the bullet’s high velocity, it is the aim of this experiment to
determine if the increase in distance from the target allows for ample time to
notice a difference in impact force upon the target. Researching the physics
principles that will be used provided valid definitions for force, such as “an
agency or influence that if applied to a free body results chiefly in an
acceleration of the body and sometimes in elastic deformation and other
effects” (Benford), however, for this experiment it must be defined as
the amount of clay displaced by the bullet’s impact with the bullet-proof vest
(this process will be described in greater detail in the methodology). In order
for this definition to be applicable, it is necessary to ensure both the type
of gun and type of vest used remain constant during this experiment. Using
helpful data from a ballistics chart (Remington), four different types of guns
were selected: a .40 handgun, a .45 handgun, a glock .22, and an M-4 submachine
gun. Choosing the vest, however, was more difficult, as it was necessary to
research both the kinds of bulletproof vests (Bullet Proof Me Body Armor), and
how each type works when stopping a bullet (Reliance Armor Systems Inc). Using
help from the FBI, were able to gain access to, and use, an appropriate type of
vest. I believe that as the distance from the target
increases, the amount of force displaced in the clay behind the bulletproof
vest will decrease in an inverse relationship due to increased quantities of
air friction, drag, and gravitational effects resulting from an increased
amount of time the bullet is in the air, despite the fact that the increase in
time is so minuscule. This result should hold constant in each type of gun,
because though each gun varies in power, the change in distance should yield
similar results, even if numbers vary.
The methodology for this
experiment was somewhat difficult, and required a fair amount of resources
which were luckily at hand. Items necessary were as follows: Water, blocks of
clay, wooden door frame, wooden stand, duct tape, bullet proof vest, measuring
cup, .40 caliber pistol, a .45 pistol, a glock .22, an M-4 submachine gun, and
protective safety gear (ear plugs, ear muffs, goggles).
Several different types and
brands of clay were looked at for usage with consideration for size,
durability, and price. In the end, three blocks of approximately 6x6 inches of
pottery clay were bought. A date was set up with an FBI agent contact over the
course of several weeks, with some rescheduling due to last minute conflicts or
problems on both ends.
The experiments were conducted
at the FBI shooting range in Vancouver, Washington. At the shooting range, the
wooden door frame was set up so that it would be possible to fire at the target
from multiple distances up to 50 yards. Once the door frame was in place, the
wooden stand, which had a height roughly half of the door frame, was placed in
the center. The vest was then secured above the stand across the door frame,
with the clay firmly secured to the back of the vest with the duct tape.
Once the vest and clay were set
up, a trained FBI agent secured the area so that no one was in any danger,
removed the pistol from his holster, and fired a single shot at the vest from a
specified distance. Safety gear was on at all times. After the shot was fired
and the weapon was re-secured into the agent’s holster, the clay was removed
from the vest and examined. The impact crater left in the clay was then
carefully filled with water, and the water was emptied into a measuring cup.
The results were recorded with details on the distance from the target and the
size of the crater (measured in mL of water). After the water was removed from
the clay, the clay was then re-shaped into a firm block so that it may be
re-used. While this was being done, another person was setting up the clay and
vest on the wooden stand again so that another trial would be ready as soon as
possible.
The clay was fired at from five
different ranges with each gun, each range consisting of three separate trials.
The first range was 3 yards away from the target. The second range was 10
yards, the third 25 yards, the fourth 35 yards, and the fifth was 50 yards.
Because this experiment was a
comparative study, attempting only to find a relationship between two things,
no calculations were needed or could be used. Although with more high-tech
equipment and a large budget, it would have been possible to conduct this
experiment in such a way that calculations could be used, this was simply not
the case for this study.
This here’s the link to the data.
The results which were attained
were somewhat surprising. They did not appear to agree with the hypothesis at
all, but rather seemed random and scattered. These results could mean several
things.
It is possible that the results
simply show that the distance from the target makes no difference in the amount
of force that is distributed upon impact. When reading the results without much
thought, that is what they show. However, there are a great many possible
sources of error that could be significantly altering the results.
One source of error, and
possibly the greatest, is the clay itself. While attempts were made to make
sure the clay was in the same condition for each trial, it is more than likely
that the clay was changing after every usage. For one thing, the water which we
used to measure the size of the impact crater could have been significantly
softening the clay, making it more susceptible to morphing and creating larger
craters. Also, when the clay was re-molded into a solid block after each trial,
it is possible that there were unseen pockets of air within the clay, which
again may have significantly altered the clay’s susceptibility to morphing.
Lastly, it is possible that as the clay was worked more and more, being morphed
and re-modeled over and over again, it became softer and more malleable. This
also would have led to significant inconsistencies in the results.
Another potential cause of error
could be the setting up of the clay and vest. Although it was attempted to have
them both set up on the stand the same way each trial, it is likely that there
were slight mistakes made. The clay could have not been secured to the vest as
tight as an earlier trial, or perhaps secured tighter. The tape could have been
fastened not as well as it should have been. These little errors could have
caused enough difference that the impact would be affected and the results
changed.
Yet another source of error
could have come from the FBI agent who fired the pistol. Although his aim was
extremely accurate and consistent, there could have been slight, nearly
unperceivable changes which could have slightly altered the affect the bullet
had on the clay. The angle which the bullet impacted the vest, and perhaps the
exact spot where the bullet hit, could have made slight differences in the
amount of force distributed. These differences were most likely fairly
inconsequential, but would only have contributed to the error created by other
factors such as the changing condition of the clay.
One more possible source of error
lies within the act of firing a gun itself. While each shot appears to be more
or less the same, there could have been any number of small inconsistencies.
The exact amount of force which ejects the bullet from the barrel most likely
is not exactly the same for every shot. Additionally, although there were no
extreme changes in weather conditions, slight differences could have altered
the results as well. A light breeze for one shot but not another could have
added additional wind resistance to the bullet, altering the size of the impact
crater. Even the tiniest differences, such as a shift in humidity or
temperature, could possibly have made the slightest change, adding on to the
errors from other sources.
There are perhaps some things
which could have been done differently to produce more accurate results. Using
an indoor shooting range instead of an outdoor one could be a solution to
uncontrollable changes in wind, temperature, humidity, and weather. Also,
having a more advanced set up than wood and duct tape could have improved the
accuracy and consistency of the results. This could have been done by creating
a base on which to place the clay and vest which would have them consistently
set up more in a more exact position, rather than simply using materials which
were at hand. Also, perhaps the clay which was used was not the material best
suited for this situation. Although there is gel which scientists use for
exactly these sort of tests, it is very expensive and difficult to attain and
would not be practical for a high school student to use. However, there may be
better types of clay available which would not change so drastically with use
or be susceptible to breaking down in water.
The only results which can be
seen, though it has nothing to do with the original hypothesis, is that as the
caliber of the gun increases, the general size of the impact crater also
increases. Because of this great deal of potential error within the experiment,
all that can be said in conclusion is that the results were inconclusive, and
perhaps a better budgeted and more sophisticated, well-thought out set up could
produce more accurate results.
Ammunition Ballistics. Remington. 2004. Retrieved on November 1, 2004. <http://www.remington.com/ammo/ballistics/ballistics.htm>
This
website provided information on different types of ammunition.
Benford, Gregory.
World Book Encyclopedia, vol 7. World Book Inc, Chicago, 2000.
This
encyclopedia provided information on guns in general.
Body Armor & Tactical Equipment. Reliance Armor Systems Inc. May 24, 2004. Retrieved
November 1, 2004. <http://www.profilon.us/reliancevest.htm>
This
website provided information on bullet proof vests.
Bullet-Proof Vests. The Free Dictionary. Farlex Inc. 2004. Retrieved November 1, 2004.
<http://encyclopedia.thefreedictionary.com/bullet-proof%20vests>
This
website provided additional information about bullet proof vests.
Bullet proof Vests to put
the odds in YOUR favor. Bullet Proof Me Body Armor. 2004.
Retrieved on November 1, 2004. <http://www.bulletproofme.com/NIJ_Test_Rounds_CHART.shtml>
This website also provided additional information
about bullet proof vests.
Giancoli, Douglas. Physics – Principles with
Applications (5th Ed.). New Jersey: Prentice Hall, 1998.
This
physics classic provided information about the physics aspects of the
experiment.
Trefil, James.
1001 Things Everyone Should Know about Science. Doubleday: New York, 1992.
This
book provided a little additional information about the physics applications of
this experiment.