Bullet Velocity - Research Paper Example

A bullet is a metallic projectile loaded in cartridges and fired from firearms, the cartridge consists of a cartridge case, propellant charge, primer, and bullet. Pulling the trigger strikes the primer which in turn ignites the gunpowder, high pressure is built which propels the bullet forward and ejects the casing. The flight path of a bullet includes travel down the barrel, path through the air, and path through a target or wounding (Fackler, 1996). The burning gunpowder produces pressure given by Force divided by Area and the larger the barrel the greater the acceleration of the bullet.

It is difficult to measure forces within the barrel but the velocity at which the bullet exits the barrel (muzzle velocity), can easily be calculated (Bruner et al, 2011), and is given in feet per second. Bullet velocities are classified as below 1000 fps, 1000-2000 fps and above 2000 fps as low, medium and high velocity respectively. (Wilson, 1997) (Wilson, 1997) Bullet Velocity Initial/Internal Ballistics Pressure exerted on the bullet by the burning powder is given by Pressure=Force/Area Whereby: Area = base of bullet= diameter of barrel = constant Energy transmitted to the bullet thus depends on: 1.

Mass (ponds) 2. Time of travel (seconds) 3. Time interval over which force is applied (seconds) 4. Barrel length (metres) The pressure and time is related as shown in the graph below Pressure Time over which force is applied As the bullet travels through the barrel, it phases minor deformations called setbacks resulting from imperfections in the barrel, however, the effect of this deformations are negligible (Jandial et al, 2008) External Ballistics/In Air to the Target This can be determined from Kinetic energy formulae as follows: Let: m=mass of bullet a=acceleration of the bullet x=distance travelled From Newton’s second law F=ma ……………(1) Then; Work done is given by work done=ma(x) From the expression v2=u2+2ax (Zitzewitz et al, 1995) Where: v=final velocity u= initial velocity =0 since the bullet starts from rest Thus; a=v2/2x ………………… (2) Substituting eqn(2) into equation of work Work done = mv2x / 2x ……………… (3) Since work done=Kinetic energy Kinetic energy of bullet, KE=mv2 2 Rearranging for velocity V2 = 2KE M Velocity, V= (2KE M) …………….(4) OR Let W = Weight in grains.

Then M = W/ (7000grains per pound 32 ft/s) where: 32 ft/s – gravitational acceleration Kinetic Energy = WV2/450435 ft/lb Hence velocity, V= (KE450435 W) This is the bullets velocity as it leaves the muzzle. This velocity is affected by Drug as it heads towards the target. Let f (v/a) - ratio of velocity of bullet to velocity of sound in the medium of travel k- Constant for shape of the bullet &- constant for yaw p- Density of medium d- Diameter of bullet Drug, D = f (v/a) k&pd2v2 The degree to which a bullet is slowed by drug is called retardation given by Retardation, r = D/M Velocity is thus given by misery Velocity, V = (KE450435 W) – D/M A bullet fired straight upwards will slow down, stop and fall back to earth obeying the lows of free fall.

It accelerates until it reaches a point where its weight equal to resistance of the air, this velocity is called terminal velocity (Cecil 2012). The formulae for free fall is expressed as V= ? gt where: g—gravitational acceleration t—time of fall References Bruner D, Gustafson CG, Visintainer C. Ballistic injuries in the emergency department. Emerg Med Pract. 2011;13(12):1-30. Cecil Adam, Retrieved from http://wiki.answers.com/Q/Formula_for_velocity_of_a_bullet Fackler ML: Civilian gunshot wounds and ballistics: dispelling the myths.

Emerg Med Clin North Am. 1998;16:17-28. Jandial R, Reichwage B, Levy M, Duenas V, Sturdivan L. Ballistics for the neurosurgeon. Neurosurgery. 2008;62:472-480. Wilson JM: Wound ballistics. West J Med. 1977;127:49-54. Zitzewitz, Paul W. & Robert F Neff. Physics: Principles and Problems. New York: Glance, 1995: