On Wikipedia they list bullet velocity and energy, some bullets have different sized bullets so have a list.
The measurement for energy is ft lbs. (Or at least I understand that one better.) And while I do understand a bullet can do a significant amount of damage to an object, I don’t understand what the ft lbs means. Case in point, for the 500 S&W magnum round they have 5 different bullets velocity and energy listed. The bullets listed have low 2000 ft lbs to almost 3000 ft lbs listed.
My understanding of “1 ft lbs” is the amount of energy a 1 pound weight hits the ground with. (In a vacuum) Or the amount of energy needed to raise 1 pound 1 foot in a vacuum.
So while the 500SW magnum is a very powerful round, I know it can’t move 2000-3000 pounds a foot. So I want to know what the ft lbs means in this case? Like if a person is shot they don’t really fly back. There is a video on YouTube where a guy shot a 5 gallon water jug. It caused the jug to split and water to fly everywhere, but it didn’t move.
Am I not understanding ft lbs to start with? Or what? How does a bullet have that much energy, but in reality can’t move an object even close to the size listed?
In: Physics
Your understanding of what a foot pound is is correct. The reason that it doesn’t push the jug is because it doesn’t transfer much of its energy to the jug – if you shoot a plastic jug with a gun, the bullet will pass straight through and not lose all that much velocity, which means most of the energy is still in the bullet.
In the case that the bullet embeds itself in the person, a lot of its energy will be spent deforming things (breaking your bones, tearing through muscle etc all takes energy to do).
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