Old College Physics Paper I wrote that I thought was interesting due to it's indirect effects on our world's economy, politics, and society...
I watched a fascinating episode on the History Channel called "Modern Marvels", this episode being about the invention and evolution of the bullet. I found it a fascinating program because it began with the origin of the bullet, the transitions and refinements it went through over hundreds of years, and finally the various types of high-tech bullets that are being used today.
Bullets are solid projectiles of metal such as lead because of its density and cost-effectiveness and is fired from a firearm, a gun of some sort. As we have studied in class, projectiles have parabolic vertical motion due to air resistance as well the force of gravity (Fdownward = mass x gravity) pulling it downward. The bullet is encased with a shell, explosive, and a primer, this combination is properly referred to as a round or cartridge. The bullet itself damages its target by exerting its Kinetic Energy (.5mv^2) on it. An original musket bullet was wrapped in a loosely fitting paper patch which formed a tight seal so the pressure of the expanding gas would push the bullet out of the muzzle. Bullets started out as small lead balls around 1500 and changed very little despite firearm advancement up until 1800. The bullet’s shape first changed in 1826 when British Army soldier John Norton started making bullets with more of a flatter and hollow base that would expand wish the pressure of exploding gases but it was rejected. In 1836 William Greener invented his Greener Bullet which was very similar to Norton’s except his had a wooden base which more effectively was pushed by the expanding gases out of the firearm barrel. In 1947 it evolved even further with the Minie Ball that had the same cone shape but a small iron cap in the back instead of a wooden plug and these bullets accounted for approximately 90% of the casualties suffered in the American Civil War. In 1862 the next wave of bullets called the Lee-Metfords were created by Metford and used a spiraling action and a longer pointier bullet to increase effectiveness. The final major advance in bullet design occurred in 1883 with the invention of the copper plated pointed bullet which allowed for much higher velocities and bullet kinetic energy to be achieved as well as reducing chances of clogging the barrel with melted lead from the hot expanding gases. These “spitzer” bullets were very lethal especially when combined with the new machine guns and caused devastating damage in wars ever since, most notably World War I and World War II. This bullet shape helped to improve aerodynamics by reducing air resistance that would thwart the bullet’s kinetic energy and accuracy.
The effective bullets these days form a very tight seal with the firearm’s bore to maximize the effectiveness of the expanding gases at the back of the bullet. This allows a greater amount of force to be exerted on the bullet as it is propelled out of the chamber. They also have shells that reduce the force of friction with the firearm’s barrel so less speed and energy are lost during this movement since Fnet = Force exerted – Force friction. The rotational force that the rifle exerts on the bullet will help to avoid any significant inaccuracy due to the fact that the centripedal forces should help keep the bullet going relatively straight despite imperfections in the bullet shape. Another way to maximize aerodynamic efficiency and accuracy for the bullet is to design the bullet with the majority of weight in the front end.
There have been several advanced forms of the bullet invented in the past century. The armor piercing bullets contain a flat or pointed tip and are filled with extremely dense metals such as steel to penetrate armor. These bullets have increased mass which means increased momentum and kinetic energy. Tracer bullets are filled in the back with metals that react to the explosion by forming temporary bright red salts. Incendiary bullets are tipped with explosive materials to add to the devastating power of the bullet. Although all of these bullets are quite deadly, ironically the Geneva Accords on Humane (I think this is particularly hypocritical) Weaponry and the Hague Convention outlaw the use of exploding, expanding, and poisoned bullets. All of the bullets mentioned however have to follow the internal and external laws of ballistics and must be aerodynamically sound to be effective.
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