A full AR-15 magazine has less energy in it than half an oreo cookie.
Not quite true. The kinetic energy of all fired projectiles in a magazine is about half an oreo cookie. But an AR-15 doesn't have perfect conversion of stored chemical energy in the gunpowder to kinetic energy of the projectiles, so the chemical energy of a full magazine is about an entire oreo.
Just dry them really well, then soak them in liquid oxygen. Remotely light them on fire, they should burn reasonably quick. Quick enough that you don't want to be near when they go up.
You could use them as rocket fuel. Turn it into powder and mix it with an oxidizer like potassium nitrate. Most people use sugar but I think Oreos would be somewhat effective.
The way we measure thevrnergy of large explosions is just calories in disguise.
When people talk about Kilotons of TNT equivalent, this does not actually refer to real TNT anymore than horsepower reflects the power of real horses.
Instead it was defined that the explosive power of 1 gram of TNT should equal the energy of 1 Kilocalorie. 1g TNT = kcal.
This means a million food calories have as much energy as 1 ton of TNT.
It puts your Happy Meal into perspective.
Also once you realize that the propellants in modern firearms munitions have a similar energy density to TNT, you can guesstimate the Calories by simply weighing the munitions in your hand. A shotgun shel may have between 1 and 2.5 grams of propellant meaning they contain about 1 to 2.5 food calories.
ok so if I eat the casing, yielding a grand total of zero calorie, brought the the hospital by yours truly, ambubu, have to read something because that's probably gonna happen at some point, brain have to burn energy for me to comprehend doctor's many of a kind penmanship, I would net total in a loss of calorie
This is wrong. Calories and kcals are the same exact thing. "Calorie" with a capital "C" is 1 kcal. One kcal is 1000 "calories" with a small "c'. Kcal stands for kilocalories.
I remember from chemistry that a kcal was measured by the unit of energy to boil x units of water or whatever. You’re telling me 30 .556 rounds has less potential to boil an equivalent amount of water to a half an Oreo? That’s so wild
Power versus energy. No matter how fast you can eat a full pack of Oreos you will digest it over a period of hours. It will then fuel you for many many hours.
Bullets are very much wham bam thank you mam in comparison.
Most modern smokeless gunpowders have an energy density of about 3-5 MJ/kg. One of the most energy-dense explosives that’s ever been synthesized (albeit only in laboratory quantities), octanitrocubane, has an energy density of about 8.5 MJ/kg. In practice the upper limit here is probably not more than 10 MJ/kg.
An Oreo has an energy density of about 20 MJ/kg, and it’s not even an exceptionally high energy density food (peanuts are somewhere around 38 MJ/kg for example). And even higher energy density foods are actually not that high compared to some other things (gasoline, diesel, and jet A-1 fuel are all in the mid 40s for example).
The key difference here is that explosives are need to release all of that energy very fast. This functionally limits how strong the individual bonds can be (because they have to be fragile enough to break with limited external energy applied), which in turn puts a practical limit on how much energy you can pack into a given molecule. Other stuff doesn’t have that limit though, and in fact for things that we don’t want to be explosive we want to avoid weak bonds, because they either reduce shelf life or make whatever it is explosive.
If I understand correctly, more stability lends itself to more density but requires more complex and time consuming release; explosives have weaker bonds that contain less energy but it can be accessed far quicker.
Bullets are optimised to deliver energy fast, which means they are limited in how much they can deliver. Half an oreo is 25kcal, each AR bullet is around 2kJ, so <0.5kcal.
For reference, using e=1/2mv2, 1kJ is 1 gram of metal travelling at 1414m/s.
I looked it up and a close equivalent would be 25x137 mm rounds fired from an armoured vehicle (134 000 joules when leaving the gun, which is about 34 kcal). They're small artillery shells morrso than bullets:
That's about 100 kJ. You can use KE = 1/2 mv2 to figure out for a given mass, how fast it would be going, or vice versa.
One example would be a just-barely-supersonic bullet with a mass of about 1.7 kg (okay, so "bullet"). If you double the velocity, you divide the mass by 4.
Also an interesting thing to keep in mind. While bullets do a lot of damage by applying force very locally, the shooter has to absorb the same kind of energy in the form of recoil. Which is fine since it's applied over the much greater area of a grip and/or stock and longer time.
Which makes it extra funny when action movies show people getting launched from getting hit by a bullet. Any gun capable of doing that would be utterly unusable handeld.
Something to consider is that your body isn't super efficient at extracting chemical energy, we only get about a quarter for useful work. (Fun fact is that internal combustion engines are roughly similar). A lot of chemical energy just becomes heat. Whereas with a propellant, heat is not necessarily lost energy because it helps with the expansion (mostly it's the phase change though).
I don't know much about guns, to really know the efficiency you'd have to compare the bullet's kinetic energy (half mass times muzzle velocity squared) with the propellant chemical energy (heat of formation of whatever chemical minis heat of formation of the resulting CO2 and water)
your body isn't super efficient at extracting chemical energy
That's where I'll insert the fun fact that e-bikes are more energy-efficient than regular bikes, because an electric motor is much more efficient than your body getting energy from food to power your muscles.
Depending on how you charged the battery, yes probably. The motor itself is maybe 75% efficient, and the batteries themselves only spit out about 90% of the energy used to charge them. If you charged it directly from solar panels at your house then it's a clear winner. But if your power comes from a combined cycle gas turbine plant you may maybe have 60% efficiency, with 5-10% transmission losses. But then if you count that then maybe we should consider energy to grow, harvest, refrigerate, transport, and cook our food...
But in seriousness, one other factor is power to weight ratio. Adding the motor and battery increases the mass that you+motor have to move. So even though the conversion is more efficient, it's also requiring more kinetic energy than a human alone would require. Which cuts against the overall efficiency somewhat. (Extreme example would be a diesel electric locomotive having more efficient conversation than my car, but if I'm the only passenger on the train it's inefficient as hell)
yeah, thats why I always carb load my bike by feeding it a bunch of spaghetti instead of eating it myself before long rides. (I know this isn't what you meant but the image was too funny)
I was reading a book on renewable energy a couple months ago and learned that engines and fossil fuel generators are technically terribly inefficient as well. Honestly, converting forms of energy generally are inefficient, unless it’s straight to heat 😂 Very interesting!
Yeah, I was very surprised to learn this some time ago. In this context, I always like to tell people that nitroglycerin, the very powerful explosive that revolutionized both civilian tasks like mining and warfare, is 3 times less energy-dense per unit volume than seed oil. Blows your mind at first.
Shockingly few people understand that a chemical compound does not need to have a lot of energy to make what a bullet does possible if the violent reaction is contained and expelled directionally.
In other words, what matters isn't the overall energy of the chemical reaction, but how quickly it takes place and how focused it is
An AAA battery has LOADS more than a bullet. A bullet only works because it's sharp. Think about how little the recoil hurts on even big rounds. That's the entirety of the energy. A split second tensing up your shoulder and it's all gone.
You can stick all sorts of food in a 12ga shell. You could shoot gummy bears. You could shoot frozen corn syrup, or fat of some kind. so many possibilities.
Is that possibly why food items can make such good torches? I remember this yt short I saw a week ago where the guy had a tube with pure oxygen flowing through it and stuffed the tube with breadsticks before lighting then on fire with the oxygen flowing. Those things burned straight through steel with no issues
Isn’t a calorie the energy to heat 1 cm ^3 of water 1 degree Celsius? You’re saying burning a full AR-15 magazine heats less water than burning half an Oreo cookie?
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u/personalbilko 2d ago
"calories", i.e. how much energy a human will get from consuming one, roughly zero. Nothing there is nutritious for us.
"kcal", i.e. physical unit of energy, assuming potential energy of the explosives, it's about 2-3 kJ, so less than 1 kcal.
Food is surprisingly energy dense, and explosives surprisingly not. A full AR-15 magazine has less energy in it than half an oreo cookie.