arXiv subjects

Michael Courtney

Publications and source records attributed to Michael Courtney.

65 records · Page 4Linked to original sources

arXiv2008

The Ballistic Pressure Wave Theory of Handgun Bullet Incapacitation

This paper presents a summary of seven distinct chains of evidence, which, taken together, provide compelling support for the theory that a ballistic pressure wave radiating outward from the penetrating projectile can contribute to wounding and incapacitating effects of handgun bullets. These chains of evidence include the fluid percussion model of traumatic brain injury, observations of remote ballistic pressure wave injury in animal models, observations of rapid incapacitation highly correlated with pressure magnitude in animal models, epidemiological data from human shootings showing that the probability of incapacitation increases with peak pressure magnitude, case studies in humans showing remote pressure wave damage in the brain and spinal cord, and observations of blast waves causing remote brain injury.

physics.med-ph↗

arXiv2007

Sheep Collisions: the Good, the Bad, and the TBI

The title page of Chapter 9 in Fundamentals of Physics (Halliday, Resnick, and Walker, 8th Edition, p. 201) shows a dramatic photograph of two Big Horn sheep butting heads and promises to explain how sheep survive such violent clashes without serious injury. However, the answer presented in sample problem 9-4 (p. 213) errs in presuming an interaction time of 0.27 s which results in an unrealistically long stopping distance of 0.62 m. Furthermore, the assertion that the horns provide necessary cushioning of the blow is inconsistent with the absence of concussions in domestic breeds of hornless sheep. Results from traumatic brain injury (TBI) research allow acceleration tolerance of sheep to be estimated as 450 g facilitating an analysis of sheep collisions that is more consistent with available observations (stopping distance less than 1 cm, impact time of roughly 2 ms).

physics.ed-ph↗

arXiv2007

Relative incapacitation contributions of pressure wave and wound channel in the Marshall and Sanow data set

The Marshall and Sanow data set is the largest and most comprehensive data set available quantifying handgun bullet effectiveness in humans. This article presents an empirical model for relative incapacitation probability in humans hit in the thoracic cavity by handgun bullets. The model is constructed by employing the hypothesis that the wound channel and ballistic pressure wave effects each have an associated independent probability of incapacitation. Combining models for these two independent probabilities using the elementary rules of probability and performing a least-squares fit to the Marshall and Sanow data provides an empirical model with only two adjustable parameters for modeling bullet effectiveness with a standard error of 5.6% and a correlation coefficient R = 0.939. This supports the hypothesis that wound channel and pressure wave effects are independent (within the experimental error), and it also allows assignment of the relative contribution of each effect for a given handgun load. This model also gives the expected limiting behavior in the cases of very small and very large variables (wound channel and pressure wave), as well as for incapacitation by rifle and shotgun projectiles.

physics.med-ph↗

arXiv2007

Ballistic pressure wave contributions to rapid incapacitation in the Strasbourg goat tests

This article presents empirical models for the relationship between peak ballistic pressure wave magnitude and incapacitation times in the Strasbourg goat test data. Using a model with the expected limiting behavior at large and small pressure wave magnitudes, the average incapacitation times are highly correlated (R = 0.91) with peak pressure wave magnitude. The cumulative incapacitation probability as a function of time reveals both fast (t < 5 s) and slow (t > 5 s) incapacitation mechanisms. The fast incapacitation mechanism can be accurately modeled as a function of peak pressure wave magnitude. The slow incapacitation mechanism is presumably due to blood loss via damaged vascular tissue.

physics.med-ph↗

arXiv2007

Review of criticisms of ballistic pressure wave experiments, the Strasbourg goat tests, and the Marshall and Sanow data

This article reviews published criticisms of several ballistic pressure wave experiments authored by Suneson et al., the Marshall and Sanow "one shot stop" data set, and the Strasbourg goat tests. These published criticisms contain numerous logical and rhetorical fallacies, are generally exaggerated, and fail to convincingly support the overly broad conclusions they contain.

physics.med-ph↗

arXiv2007

The Truth About Ballistic Coefficients

The ballistic coefficient of a bullet describes how it slows in flight due to air resistance. This article presents experimental determinations of ballistic coefficients showing that the majority of bullets tested have their previously published ballistic coefficients exaggerated from 5-25% by the bullet manufacturers. These exaggerated ballistic coefficients lead to inaccurate predictions of long range bullet drop, retained energy and wind drift.

physics.pop-ph↗

arXiv2007

An Acoustic Method for Determining Ballistic Coefficients

This paper presents a method for using a PC soundcard, microphone and a chronograph to determine bullet BC with an accuracy of 6%. This is useful when a second chronograph is unavailable or when the projectile accuracy is insufficient to use a far chronograph.

physics.pop-ph↗

arXiv2006

Acoustic measurement of potato cannon velocity

This article describes measurement of potato cannon velocity with a digitized microphone signal. A microphone is attached to the potato cannon muzzle and a potato is fired at an aluminum target about 10 m away. The potato's flight time can be determined from the acoustic waveform by subtracting the time in the barrel and time for sound to return from the target. The potato velocity is simply the flight distance divided by the flight time.

physics.ed-ph↗

arXiv2006

Teaching Fourier Analysis and Wave Physics with the Bass Guitar

This article describes a laboratory or demonstration technique employing the bass guitar and a Vernier LabPro (or a PC soundcard) for teaching wave physics and introducing Fourier analysis. The Fourier transform of an open string provides a demonstration of oscillatory modes out to the 20th harmonic consistent with expectations containing a fundamental frequency and harmonics. The playing of "harmonics" (suppressing resonant modes by lightly touching the string to enforce nodes at desired locations) demonstrates oscillations made up (mostly) of individual modes. Students see that the complete set of Fourier components (fundamental and harmonics) present on the open string can be explicitly connected with individual resonant frequencies as described in typical textbook discussions of natural frequencies of waves on a string. The use of a bass guitar rather than the six string electric guitar allows higher harmonics to be individually excited, and it is also easier for students to play the harmonics themselves.

physics.ed-ph↗

arXiv2006

Five Frequently Fatal Freshman Physics Fantasies

This article describes five common student misconceptions about succeeding in college-level Physics courses: the miracle finish, the soft hearted professor, an extension of high school, weak areas won't be tested, and passing is more important than learning. These fantasies are unique to neither Physics nor freshman, but the challenge of learning Physics brings more certain negative consequences to students retaining these attitudes. Ascribing these student misconceptions to freshmen acknowledges that they diminish with increasing academic maturity.

physics.ed-ph↗

arXiv2006

Measuring Bullet Velocity with a PC Soundcard

This article describes a simple method for using a PC soundcard to accurately measure bullet velocity. The method involves placing the microphone within a foot of the muzzle and firing at a steel target between 50 and 100 yards away. The time of flight for the bullet is simply the recorded time between muzzle blast and sound of the bullet hitting the target minus the time it takes the sound to return from the target to the microphone. The average bullet velocity is simply the distance from the muzzle to the target divided by the time of flight of the bullet. This method can also be applied to measurement of paintball velocities.

physics.ed-ph↗