Paradox of Egg Breaking

[ravisbassi]

This is something I have known since my hostel days at IIT Delhi in the seventies. I have wondered many times, and this could be a research topic.

If you take two eggs one in each hand, and then hit them one against the other, only one will break. That is how I break eggs, and for the last one left I have to hit it against the plate or fork ot whatever. When you hit the two eggs together, I never had to worry about small shell fragments. Try it yourself. Never once in the last 30 plus years have I broken them simultaneously.

Let us say Egg 1 (E1) and E2

You break E2. Then hit E1 and E3. Either E1 or E3 will break, and so forth.

Try it. Never fails. I have done it thousands of time.

My academic challenge to the forum - what is the mathematics/physics/material science behind this ? Please free to share with non CEA members. Someone can probably get a PhD for this, I hope.

[avscorreia]

I'm pretty sure that you if try to hit them hard enough, they will both break, even if it's just the squashing against both your hands. It's just a matter of momentum... ;)

[ravisbassi]

I'm pretty sure that you if try to hit them hard enough, they will both break, even if it's just the squashing against both your hands. It's just a matter of momentum... ;)

avscorreia - Please try. I will buy you a carton to do so. It is not a question of squashing them, and thereby the momentum. I am talking of hitting one egg against the other with the same force that you will use if you had to hit it against the countertop to break it to make an omellete or scrambled eggs, etc..

Please try. You will be surprised.

[avscorreia]

I know, I know. I was just making a joke... didn't work... :)

[hamycta]

Well I think it's all about the chemistry of eggshell, and the percentage of calcium from it. I think the strenghten of the eggshell depends on that and that's how the stronger eggshell will crush the other one.

[brass]

hi ravisbassi, I'll give you my thoughts on it and I hope I am not discouraging anyone from writing a phd about it :mail1:

The mechanics of the egg breaking that you mention is dependent on the following main factors:
1. The geometry of the egg shells
2. The mass of the eggs
3. The force that you apply to each one of them
4. The respective crash spot on each egg
5. The material composition & density of the shells

If you want to make sure that both your eggs will be broken at the same time, make sure that the 5 factors above are the same in both eggs. Unfortunately that cannot happen because:
1. There are not two eggs with the identical geometry (i.e. 100% identical)
2. There are no two eggs with the identical mass (i.e. 100% identical mass, in every atom)
3. The force that you apply is different, your arms don't have the same strength and also they are controlled by two different brain hemispheres, this makes them have different degrees of control, speed, force etc.
4. Suppose you can fix somehow 1, 2 & 3. Still you have to make sure that you hit them in the respective spot (i.e. not head with bottom, head with middle and so on), you need some damn expensive lasers to calibrate the hit spots :wacko2:
5. Last but not least, the material composition and density can't be the same, ever, not even from the same chicken. :dash2:

However, if we make use of some physics we can see that:
m1 x V1^2 /2 (Kinetic Energy of egg 1) + m2 x V2^2 /2 (Kinetic Energy of egg 2) = Energy is transformed to heat + energy that is used to deform shells + energy that is used to break shell(s) + Kinetic energy of the broken shell pieces and egg fluid that escape their initial position within the egg.
Most of the energy I guess goes for breaking the shell and as kinetic energy of the broken shell pieces and egg fluid that escape. So if you want to maximize the probability of breaking both eggs upon impact, I suggest you do the following:
1. Choose two eggs that appear to you as having the same geometry and mass (this can take some time and money, but if you want to get an answer ..... )
2. Tape the eggs with duct tape, several times, just leave out the hit spot and a small area around it, for example the top. (the taping will act as reinforcing for the shell, and even when it will break, the pieces will not fly around and the fluid neither, so you remove the kinetic energy of the pieces from the equation and hopefully that extra energy will be enough to break the shell of the other egg)
3. Extend your arms 180 degrees apart and make them meet with the highest speed. Do this movement in a certain plane, use a desk or flat surface to guide you. Try with some tennis balls before you try with the eggs).

Enjoy!

[ynopum]

But why someone would expect that both eggs should broke?
By the way, on Easter if you break boiled eggs sometimes it happens that both eggs brake. The last year in my family there was no winner, because of that.

Of course the boiled eggs are significantly stiffer, and the shell doesn't collapse compared to the raw ones.

If you think a lot on this, let me give you a contra-question, and you'll see why if after one egg gets even microscopic crack - it can't beat the other egg: assume only empty shells, (make two holes and pour the egg contents) that are filled with hard material (i.e. grout). If you crash them, both shells will break, as they can't collapse. Why?

By the way, the one who gets the winner egg will get the health, and the crushed will get the wealth - so in there is no loser. :JC_cheers: