Mansplain with "2000 Joules" of energy in a bullet to me like I'm a bitch.You saying a decent bullet has the energy to move 4,000 lbs (like big car) over a yard?Even if the car was on skates on Teflon coated ice, and the bullet was full absorbed and no time limit, there seems to be something I'm just not getting.
>>64447117You’re overthinking it. It’s not a transferable energy in the sense that 2000 Joules = you can move X weight with it, it’s the direct energy that the projectile maintains. It IS the weight that’s being propelled. It’s the car, basically.
>>64447126still not getting shitalso, I guess it would be better to consider the weight as not being slid on ice, but moved STRAIGHT UP off the ground.I'm thinking a bullet would have about 1 Joule, or the energy to make a 2.2lb block jump about 3ft off the ground.
/k/ - Physics
>Nigga doesn't understand middle school physicsWasting years with memeunits and stupid analogies causes this kind of situation.
>>64447117You’re mixing up energy and force.When we say a bullet has 2,000 joules of energy, that means it has the same amount of energy as something else could have under different conditions, not that it can do the same thing.A 2,000 J bullet could, in theory, lift a 4,000-lb car by about 4 inches if all that energy were perfectly converted into potential energy, but that’s not how momentum or impulse work in practice.A bullet’s mass is tiny, so even though it’s moving fast, it carries very little momentum compared to something as massive as a car. It dumps its energy over a few milliseconds and a few centimeters of travel, meaning the power (energy per unit time) is enormous locally, but the total impulse (the ability to move large things) is small.Energy has no relevance to lethality whatsoever, it’s just a useful general metric for measuring the “power” of a round, like BMI for fat people.
>>64447217believe or not, I squeezed out a B- on college Physics w/Calc.OK, the prof was famously easy, but still.
>>64447117>JewlsStop being a euro fag
>>64447342>prof was easyyeah it shows.>>64447245you're not helping much>>64447117the kinetic energy the 2000 joule bullet has in the reference frame of the muzzle device is equal to the work performed when lifting a 20kN car 0.1 meters in a constant gravitational potential field.you will not be able to do the conversion in practice, though, without a very elaborate setup. most practical means of intercepting a bullet and trying to get it to perform work in lifting a car will have extremely low efficiency, with most of the energy going into heating shit, plastically deforming the bullet and its target or accelerating shrapnel instead
>>644471172000 joules in a bullet is more bullet per bullet
>>64447245>Energy has no relevance to lethality whatsoeverThat statement is so incorrect it’s mind boggling. This nigga thinks a bullet shot at you and a bullet gingerly tossed at you will have the same lethality.
>>64448149Shut the fuck up, midwit>>64448343Pull your head out of your own ass. I never said velocity did not have any effect on lethality did I? Nor did I say that the mass of the bullet itself did not have any effect. Those factors independently, along with shot placement and bullet construction, are what determine lethality. Pure, measured energy, means nothing. Almost zero of it is transferred to the target upon impact. Please go get a gun and shot yourself in the head with it to see the effect for yourself.
>>64447117Small thing going really fast hits like a truck
>>64447117The car has inertia, so before all the energy of the bullet can be turned into motion, it gets channeled into the deformation and destruction of a small part of the car, and ultimately into heat.
>>64448478>I never said velocity did not have any effect on lethality did I?>Almost zero of it is transferred to the target upon impact.Lmfao looks like we got another YouTube educated ballistics expert on our hands
KE=1/2mv^2
>>64447117The physical law is conservation of momentum, not conservation of energy. Bullets have low momentum for their energy because momentum is mass*velocity, whilst energy is mass*velocity^2. So you are right that the car will not accelerate to the same speed that would represent that same amount of energy.
>>64449211Post something that proves me wrong or kill yourself so we have another example to study from. You probably think hydrostatic shock is a real phenomenon, don’t you?
>>64447245Energy is the best single (!) metric available to describe lethality. And, assuming bullet weight is in a reasonable range and bullet construction optimized, a pretty damn good one.
>>64450018>Energy is the best single (!) metric available to describe lethality.No it fucking isn’t lmao. If energy killed then arrows wouldn’t. Fuck out of here.
>>64447117>>64447191Basically you're saying "I can't imagine this being true". If the car is on a frictionless surface and the bullet imparts it's energy with perfect efficiency (silently and without producing friction) then it literally is true.>>64449228>The physical law is conservation of momentum, not conservation of energyNo, it's energy, which is why entropy applies to non-mechanical systems. Momentum only applies to objects in motion, objects at rest have no momentum, but they still have energy.
>>64450040Give me a better one then.Also arrows are extra killy because they're sharp or at least very pointy. Bullets are different.
>>64449228>>64450057The only relevant energy a bullet has is it's motion energy.And both laws, both momentum and energy, apply (always). It's just that when you're shooting a bullet into a bullet catcher (like a car, or let's assume a sand bucket within the car), the interesting one is momentum, because roughly all the momentum of the bullet goes into the car (+ the remaining bullet), while most of the energy is lost as heat.
>>64450063>Give me a better one then.Think very very hard, as hard as you can, really churn those gears in your brain about how arrows actually physiologically kill their targets, what kind of anatomical damage they do to tissue, and realize how stupidly wrong “bullets are different” is.I’ll give you a hint. Death is inflicted upon an individual/living target through primarily these means:1. Blood loss.2. Damage to the nervous system. 3. Destruction of vital tissue and organs.4. Septicemia or asphyxiation.
>>64447117>there seems to be something I'm just not getting.Two things. First you're grossly underestimating the importance of friction (without it any amount of kinetic energy is sufficient to move any mass any distance, though it may take a very long time). Second you're looking at just the energy when you should primarily be looking at the momentum. The momentum of that 2000J bullet of yours, perfectly absorbed by the car, might be able to give it a speed of about 0.005 mph (rough napkin math) if friction is absolutely zero. Which with any realistic amount of friction means a speed of fucking nothing.No need to feel all too bad about it though, for some strange reason basically no one appears to have heard of momentum, despite it being as important as force and energy in mechanics.
>>64450112>I ask for a single metric>He gives me 4>And tells me I'm stupid
>>64449228>not conservation of energyEnergy is conserved too but it can change type. Fir example turn into thermal energy (of heated bullet and target form impact).
>>64450124Trying to reduce projectile lethality down to one metric that wholly fails to address the entire picture and isn’t relevant what actually happens upon impact with tissue shows how fucking stupid you are. Expand your horizons.
>>64450158Alright, oh wise one, how would you *simply* describe lethality? The next step up would be bullet weight and velocity, but you have examples of bullets on both ends of the spectrum at similar energy and their lethality is roughly equal.
>>64450174You fucking can’t. It literally cannot be reduced down to just “wun metrik!” without failing to accurately and completely understand the picture. I literally gave you the driving factors of death from a projectile to use as a starting point back in >>64450112 but you’re clearly too retarded to understand that and think critically. I’m going to post a couple of links you can read through and rub brain cells together with because I’m at work and don’t feel like typing this all out.https://www.ballisticstudies.com/Knowledgebase/Effective+Game+Killing.html>I disagree with his assertion that hydrostatic shock exists but it’s still a good read.https://rokslide.com/forums/threads/does-energy-have-the-potential-to-affect-terminal-performance.339995/>Very good forum discussion that delves deeper into the relevant factors that determine projectile lethality.
>>64450233>You fucking can’t.A metric doesn't need to be perfect or "accurate and complete". It simply needs to be better than no metric at all. Any reasonable person can understand that .22 short (100 Joule) is less killy than 9x19 (500 Joule) which is less killy than .223 (2000 Joule) which is less killy than .308 (4000 Joule), and that's the important part.
>>64450300Oh, and also rokslide blocks me, which is a shame because it seems like there's actual information in there.
>>64450300But that just circles back to what I said earlier about energy being a useful general measurement of power. It still doesn’t tell you what kind of wound will be created, what the shape of that wound will be, how deep the wound will go, and what anatomical structures that wound will damage. Bullet construction and velocity have all of the relevance there rather than just pure energy.>>64450305Shame, because it’s a good discussion. Here’s a pasted text from it that sums up what I’m saying. I can paste others if you want.>Yes, energy is a fairly useless number in terminal performance imo. The common measure used in hunting in the USA is ft. lbs. It’s an attempt to describe energy. Imo it‘s a made up number, much like HP in engines. We take two known actual measurements, mass in grains and velocity, then we put it in a formula and say this develops 2,100 ft lbs or whatever. So it sounds big, but what does it tell me? But it is about the damage the projectile does to the animal. That is the critical real thing to pay attention to and what energy can’t tell us. Ergo my focus on the known measurements, weight/velocity, and then bullet construction. I always say if ft lbs killed, arrows wouldn’t. What I have learned to pay attention to is my bullet and it‘s impact velocity. Bullet weight and construction, and then the velocity window it performs in. Those are the best indicators of what terminal performance will be. Energy does give one some idea of the potential that exists in terms of terminal performance I suppose. But often we are comparing bullets differing by a few thousands of an inch in diameter and 30-50-… grains of weight in animals that weigh 200-700 or more pounds. I'd suggest once one is to a sane minimum bullet weight/diameter, bullet construction becomes the critical component to understand. Get that right and use it in it‘s velocity window and kill stuff.
>>64450018Anon, what do you think is more lethal, a really bright flashlight or a cannonball going 300 meters per second?
Whats his channel on youtube?
>>64450388Being exposed to a 180kW arc flash for one second will kill you just as dead as catching that 180kJ cannonball>>64450386>The common measure used in hunting in the USA is ft. lbs. It’s an attempt to describe energy. Imo it‘s a made up number, much like HP in engines. We take two known actual measurements, mass in grains and velocity, then we put it in a formula and say this develops 2,100 ft lbs or whatever.Fascinating insights from a guy who apparently could not finish high school.
>>64450468>Fascinating insights from a guy who apparently could not finish high school.His poor grammar doesn’t make him any less correct. Provide a legitimate rebuttal or kill yourself. Here’s another from the same discussion.>Energy by itself isn't as useful as other numbers when comparing different sized bullet, bullets of different construction, etc. The "energy" is based on the relationship between velocity and mass. Whether a bullet expands doesn't depend on mass, it only depends on velocity. So, by talking "energy" you are two relationships away from the only thing you need to know. The useful ways to compare bullet terminal performance is bullet construction and velocity. They are the two giant factors, and everything else is of much smaller effect. For instance, we know that all Berger hunting bullets are designed to reliably "work" down to 1800fps. For any Berger bullet, we can say that the bullet will perform in broadside vitals at 2000fps with a variation of 1) penetration and 2) width of wound channel depending on the mass of the bullet. And, the variation isn't even of a big material difference. Of course, this assumes that you have been persuaded by the mountain of evidence that a 77gr "explosive match" bullet causes massive amounts of trauma, even more than mono bullets more than twice its weight. Energy isn't useful as a broad category, because the difference in energy between the 77gr and a 235gr bullet is going to be massive, even though the actual damage won't correlate to damage as closely as velocity. At most, the difference in energy is related to the variation in penetration and width of wound channel. And, to use energy the shooter has to use a bullet-specific number that is just the mass x velocity, so why not just use velocity? Just energy is meaningless, because a 235gr bullet can have more energy than a 77gr bullet, but the 235gr bullet can fail below 1800fps but the 77gr still above 1800fps will fragment.
>>64450468Uhh, no? Being zapped by an arc flash will kill you. Being exposed to the light emitted by an arcflash absolutely will not.Try again, kiddo
>>64450525Being exposed to a 180kw laser for one second will kill you though.
>>64450509Energy is poor metric for lethality.The best metric is, of 100 person shot with this bullet, how many died in 5min.A good metric is the size of the hole in the corpse.But since bullets have more or less the diameter and will all go through a body, a good metric can be the energy transferred.
>>64450549And being exposed to a 60W hairdryer for an hour will kill you ? These comparison are pointless
>>64450549Not if you're white and can bounce that shit off your pearly skin effortlessly.
>>64450573try that with a infrared laser Mr Vampire
>>64450562No, but being hit over the head for your idiocy for 1 hour as you well deserve would.
>>64450509I don't care about his grammar so much as his having no fundamental understanding of physics and his assertions that 'Energy' and 'Power' are made up numbers as opposed to real things like 'Weight' and 'Velocity'
>>64450586I hit a nerve ?
>>64450637What he’s saying is that just like horsepower doesn’t tell you anything about how fast a car actually is (it’s the power/weight ratio, gear ratios, final drive, aerodynamics, and most of all just driving the damn thing and seeing what it tops out at) because it’s just torque x RPM / 5252, so too does kinetic energy not tell you anything about how lethal a projectile is or what its terminal effects are on target.
>>64447245Anon is correct about energy transfer in the ideal case, but collisions are better thought through about momentum. A bullet embedding itself in a car is perfectly inelastic, meaning it dumps all of its momentum. m1v1 = m2v2. Wikipedia gives me 10g .308 @ 860 m/s as one round, if that hit a stationary 2000kg (~4000lb) car on teflon skates on ice the result would be the car skidding on ice at the whopping velocity of 4.3 millimeters per second, or 0.014 fps.any "real" collision you can think of dumps energy in all sorts of ways you can't really expect, so 1/2mv^2 or mgh comparisons rarely make sense for this. Both momentum and energy are of course conserved, but you can't "lose" momentum in ways you can lose energy.
