Getting Shot Isn’t So Bad For You

Posted on November 18, 2007
Filed Under Physics |

In this post we’ll be doing some simple, yet illuminating calculations.

A typical baseball weights about 150 grams and can reach velocities of up to 100 mph, or 40 m/sec, and so its kinetic energy is about K = \frac{1}{2} m v^2 \approx 120 J and its momentum about p = mv \approx 6 kg \cdot m \cdot sec^{-1} . On the other hand, the bullets of a .38 special handgun - the weapon of choice of many police departments in the US - weight about 8 grams, and have a muzzle velocity of roughly 300 meters per second. The kinetic energy of such a bullet is about K = \frac{1}{2} m v^2 \approx 350 J, and its momentum about p = mv \approx 2.4 kg \cdot m \cdot sec^{-1}. The two seem to be characterized by similar numbers, and yet we somehow expect a person shot with a bullet to drop down like a rag, and a person struck with a baseball to simply say, “ouch!”

If you’re expecting me to come up with some sort of ingenious physical explanation of this difference, you are in for a surprise. There isn’t any.

Studies conducted by the FBI conclude that most people fall down after being shot because they think they should. Most of us have been conditioned since an early age by the media to react in a certain way to getting shot. The FBI study basically noted that people who were intoxicated or simply well trained and experienced did not fall down after being shot once, unless the shot happened to have hit a critical region in the body, such as the spinal cord - and that doesn’t happen often, as less than 25% of the bullets shot at close range hit anybody at all, and a small percentage of those are lethal.

The myth that one drops dead when shot is called the one shot myth. It’s a fundamental problem most law enforcement agencies have to deal with, as most dangerous criminals - drug addicts, raging psychos and violent alcoholics - can’t simply be stopped by being shot at with a simple pistol. A rifle would do the trick, but it’s difficult to carry around and to draw quickly.

Comments

4 Responses to “Getting Shot Isn’t So Bad For You”

  1. fineline. on November 19th, 2007 12:22 pm

    i was looking for the energy conservation puzzle you did post last week.where can i find it?

  2. admin on November 19th, 2007 6:27 pm

    On the right you have “categories”. Select the “puzzles” sub-category. Another option would be to check out the November 2007 archives (the only archives available - hey, this blog is pretty young :) ) and scroll down until you find it.

    Here’s a direct link as well:

    http://www.physicallyincorrect.com/?p=21

  3. fineline. on November 20th, 2007 6:07 am

    I already know that dude: )
    but i couldn’t find your comment(posted by admin)after comments by myself and others.

  4. admin on November 20th, 2007 3:37 pm

    I have no idea what the source of the problem is. You should see all comments, as do I when I visit the site (there is a link to the comments just below the title, in case you’ve missed it). If you still encounter problems let me know and I’ll ask the programmers (who aren’t myself :) ).

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