Drain all the energy in one AA battery into a facepunching machine deliver one punch to a face. Whats the damage?

Question

shahla · Accepted Answer

Haha, you win awesome question of the day! Let's assume we're not using mass-energy equivalence here (i.e. we're not obliterating the battery's mass into pure energy). We're just using electrical energy. This site claims that an alkaline AA battery has 9360 Joules of energy. 9360 Joules is 9360 Newton-meters. Let's assume the punch is thrown over the distance of one meter (it's a roundhouse with a big windup). So, what does 9360 Newtons do to a fist over one meter? First, that energy has to move the whole arm (disregard body movement). This site has an average human arm weight of 3.216kg. Using F=ma, with F=9360N, and m=3.216kg, we find that the acceleration of your arm is 2910 meters per second squared. Plugging this into the formula for uniform acceleration (with an initial velocity of zero), we arrive at the figure that the fist hits you at approximately 76 meters per second, or 170mph. I conclude it will hurt like a bitch, QED.

Anja Jung · Answer

There is certainly enough energy in a AA to kill you. Energy in a AA alkaline is about 9360 J according to this google search result: http://www.allaboutbatteries.com/Energy-tables.html And the muzzle energy of a bullet from a colt 45 is 500 J according to wikipedia: http://en.wikipedia.org/wiki/Muzzle_energy So if your punching machine is reasonably efficient and punches you with a bullet-shaped fist, this kills the human. If it punches you with a mattress shaped fist, you will probably survive.

Evonne · Answer

Well, if I drain an AA battery into my MF Launch Box, it hits at about a [4].

Neelia · Answer

This is like good time Reddit - back when shit still didn't matter, but was interesting.

Annaclara · Answer

Facepunching machine?

SYNTHIA · Answer

Just to give a little better understanding of this. Again starting at 9360 joules in a battery. A baseball weighs about 149 grams. So lets relate this to being hit by a baseball. (1/2)m*v2 = 9360 Joules v = sqrt(2*9360 / .149) = 354.45 m/s So your face punching machine, assuming perfect efficiency roughly delivers a punch equivalent to being hit in the face with a baseball going at 800 mph.

Anbjorg · Answer

To drain all the energy in one AA battery, you'd have to completely convert its mass to energy. A AA battery weighs about 23 grams, which via E=MC2 is equal to 574.2 Gigawatt Hours. A very extreme form of death results.

Jerrome · Answer

But it doesn't just face punch... The best part is it's learning.

Jessika Muller · Answer

"Everybody seems to be interpreting "facepunching machine" as delivering the force through a surface area approximately the size of a human fist. I don't see anything in the question preventing it from being a "G.I. Joe"-size fist instead, or even smaller.  I'll go with "death", if suitably aimed. "

Savy · Answer

If it was a guillotine style face-punching machine, than a AA could probably lift a pound high enough to kill an elephant.

Verge · Answer

This is one of those curiously surprising things, like finding out that a stick of TNT and a Snicker's bar release the same amount of energy.

Collin · Answer

1 D10 + 2

Leonard · Answer

The damage? The cost of one AA battery.

Daniela Weber · Answer

TIL I learned why battery is the same word as battery

Adalbjorg · Answer

Good question, here's the answer: http://i.imgur.com/5SOkb.jpg

Jens · Answer

This reminds me of an idea I have to make a gun using AA batteries.  The idea works kind of like an air gun. Use the energy from the battery to super-heat some water into high pressure steam and use the pressure to fire the battery like a bullet :) What could possibly go wrong ? Edit: don't try this at home !

Diane-Marie · Answer

facepunching machines don't kill people, AA batteries kill people.

Nat · Answer

Time for somebody to write a new request to Mythbusters. Somebody who isn't me.

Salvatore · Answer

I think this belongs in r/askscience my friend.

Easton · Answer

If you consider a AA alkaline battery with 1.5V and 2800mAh (http://en.wikipedia.org/wiki/AA_battery), you might say the energy output is: E = 1.5V * 2800mAh * 60 mins/h * 60 seconds/min * 0.001 A/mA = 9360 W-s = 9360J In practical terms, that's the same energy output from 60 defibrillator pulses! (http://en.wikipedia.org/wiki/Defibrilator). What does this simple electrical engineer conclude? You'll fuckin' die. EDIT I'm stupid. I didn't multiply 60 enough times. :(

Nicky · Answer

It would essentially equal one Chris Brown.

Michelle Konig · Answer

About $3.50.

Eve-Marie · Answer

You call it facepunching machine. I call it my sex toy.

Pip · Answer

"In my highschool electronics class we made a simple taser/stungun w/ an array of capacitors. It would take all the power out of the AA batt. I have no idea the damage the electric discharge would do to flesh, but it could vaporize solder & blow a baseball size hole in an aluminum pie pan. The spark was very bright, big (maybe a blue ball 8") and and also quite loud. Could be a nice to have shocking gloves that burn (a little) flesh. "

tine · Answer

Now THIS is the kind of Reddit I grew up on!

RUTH · Answer

Ok, I'll hazard a guess.... First, you need a spring-loaded boxing glove. There's your face-punching machine. Then, you rig an electric motor to it, whose job it is to compress the spring, maybe by mounting it behind the spring loaded boxing glove and attaching the spring to a cord, and letting the electric motor reel up the cord. Power the motor with your AA battery. Well, we all know a AA battery has about 1 Watt-Hour of energy, which is 3600 joules, which we could pump into our spring. Now that's the optimal case, our motor/spring contraption is probably at least a little lossy as far as energy goes... so maybe what, half that? Rocky Marciano was only able to punch with around 1000 joules! So, theoretically, our motor to spring-loaded boxing glove contraption would be able to knock Marciano on his ass! Someone phone myth busters.

Kristina · Answer

Based on my knowledge of toys from the 1980's the answer is a mild grinding of gears, a dim light that flickers for two seconds and a fist that never really reaches its target.

Jenni-Leena · Answer

African or European battery?

KANDICE · Answer

I think you've designed a brand new engineering competition.

Kirsi-Maaria · Answer

Does a duracell battery just keep on punching?

Tanja Kuester · Answer

"Just because a battery has 9360 joules does not mean it can discharge rapidly. Did no ones "bullshit" detector go off when it was claimed that a single AA battery could propel seven pounds to 170 mph. "

Kirsi-Maija · Answer

Do you have the specs of the face puncher machine, and what brand of AA batteries?

Tale · Answer

Another way to calculate this, according to google, the amount of energy generated by a pro boxer in a single punch is something like 1000 joules (1028 joules according to a cursory Google search). A typical AA battery contains 9360 joules according to Google, so a single battery can deliver 9 times the energy of a pro boxers punch. Taking losses into consideration and considering a conversion efficiency of something like 30 % (I know, I know, unheard of in practice) that is around 3000 joules, so the punching machine would generate 3 times the energy of a pro boxer's punch. I am sure that would definitely injure a person bad enough to require some serious hospitalization.

Fuldem · Answer

Be honest, you're fucking high right now...

Maria Weisz · Answer

How high are you right now?

Franziska Abendroth · Answer

African or European facepunching machine?

Maryama · Answer

A standard AA alkaline battery has a nominal voltage of 1.5 V and a capacity of ~2800 mAh, or about 15 kJ of electric energy. The kinetic energy of a .50 magnum revolver round leaving the muzzle is about 3.5 kJ. The kinetic energy of a 5 kg bowling ball traveling at 75 m/s (about 11 pounds at about 168 mph) is ~14 kJ. It'll hurt like a motherfuck. You die.

cecillie · Answer

AA batterypowered waterpump into the ballast of a trebuchet loaded with a rubber fist would be my idea for an efficient facepunching machine.

SUSANNE · Answer

We are not done here.... What would happen if 9360 Joules of energy was compressed in single femtosecond laser pulse typically around 1010-15 seconds long. Well this means that The peak power of the laser pulse is 9.3601017 Watts. Now if we were to focus this pulse into a spot that is around 100 micron squared, which is equal to (.001 cm)2 = 10-6 cm2 . That means we are talking about Delivering a single ultrashort pulse of energy with a peak intensity of 9.360*1023 Watts/cm2.  This is equal to 0.9360 Zotta Watts/cm2 In conclusion, if this were possible, this battery would either a)destroy the universe b) cause a black hole or c) create another big bang and generate another universe that we could portal in and out of Aka Portal2. QED Thanks for playing

Binni · Answer

really depends on the efficiency of the machine

Drain all the energy in one AA battery into a facepunching machine deliver one punch to a face. Whats the damage?

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