what does bullet energy really mean?

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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

6 Answers

Anonymous 0 Comments

Yeah you got foot lbs right. There is enough energy to move a pound straight up by one foot, or half a pound by two feet, or two pounds by half a foot, etc.

In reality though, when shit gets hit by a bullet it moves a bit but mostly breaks. One foot pound of energy *would* be enough to move a perfectly unbreakable object a foot in the air straight up, its just no real materials are unbreakable.

You know how old cars are rigid, while new cars crumple like a soda can? Same principle in action. “Crumpling” absorbs energy from an impact.

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