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What makes guns so dangerous?
Category: Society
Published: April 24, 2013
By: Christopher S. Baird, author of The Top 50 Science Questions with Surprising Answers and physics professor at West Texas A&M University
The momentum imparted to the bullet by the gun is what makes a gun able to do so much damage. The momentum of an object equals its mass times its velocity. The momentum of an object, and therefore its ability to cause destruction, can be increased by making the object more massive or by making it go faster. Although the bullet shot from a gun is light, it is shot out at a high velocity, rendering it lethal. The bullet itself is not dangerous. It is the bullet traveling at high velocity that does the damage. Any object that is given the same momentum as a fired bullet can do just as much damage. For instance, speeding cars are more dangerous than guns.
One of the most widely used handguns, the Beretta M9, has a typical bullet mass of 0.008 kilograms and a typical muzzle velocity of 400 meters per second. Multiply these two numbers together and you get a bullet momentum of about 3.2 kgm/s. In contrast, modern cars have a mass of about 1500 kg. Traveling at a highway speed of 25 m/s (55 mph), a car has a momentum of about 38,000 kgm/s. In other words, if a car traveling at 55 mph were to plow into a crowd of people without ever putting on its brakes, it could do 10,000 times the damage of a single bullet. This is, of course, a rough estimate. The actual damage will depend on how the momentum is delivered; i.e. whether delivered by a head-on collision versus a glancing blow, or a blunt edge versus a sharp corner. Additionally, a gun has the ability to deliver many bullets and therefore can multiply the total momentum delivered, thereby causing more injury. With all of these considerations in mind, a car is still generally more dangerous than a gun. Statistics bear out this fact. According to the CDC, the annual rate of death due to motor vehicles in 2010 was 114 deaths per million people. In comparison, the annual rate of death in 2010 due to guns was 40 deaths per million people (suicide was not included in either statistic). Eliminating all cars would save more lives than eliminating all guns. Oddly, many people who would never touch a gun have no problem cruising twenty miles per hour over the speed limit and endangering the lives of all around them. Just as odd, there is a vocal anti-gun political movement, but there is little in the way of an anti-car political movement (the anti-car movements that do exist are more concerned with smog than public safety). This discrepancy suggests that anti-gun politics is driven partly by uniformed emotionalism and ulterior motives instead of sound science. The emotionalism surrounding guns is the same reason why the latest shooting almost always makes the front page of the local newspaper, but the latest car crash rarely does. All fast-moving objects with mass are dangerous, including bullets, cars, motorcycles, trucks, trains, and airplanes. Each should only be used by responsible people who have been trained and demonstrated that they can operate such machines safely.