Egg Drop Physics

  • #1

Main Question or Discussion Point

An egg is hard, but yet delicate food that people have been making contests of, for many years. But i am part of one that i lack the physics to figure out the perfect device here are the simple rules of this contest.


Holy Omelets Batman… It’s the Egg Drop Contest!
Design a egg protection device, that can be dropped from approximately 18ft and have the egg survive

INSTRUCTIONS:
1. Design an egg drop apparatus that can carry a minimum of one egg without breaking during its descent and land within the target area. (20 points)
A. Materials are not limited except that you CANNOT USE BUBBLE WRAP, GREEN CLOSED CELL FOAM, STYROFOAM PEANUTS, OR ANY MATERIAL THAT MAY CAUSE HARM TO A PERSON OR SCHOOL PROPERTY.
B. Maximum dimensions of 30cm x 30cm x 30cm. (Max of 1 Cubic Foot)

Mass must be less the 170grams, and must be able to contain and save 12 eggs on the fall to receive max points for the contest. Happy Halloween


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What would you all say is the best idea?
My current plan:
1 cubic foot box, which i create a duct tape and rubber band suspension system holding the egg in the middle of the box, with rubber bands going to each side, so on impact the rubber bands absorb the shock and stop the eggs from hitting the side of the box. Along with that i plan to line the box with some type of water layer or air filled bags to protect the eggs from the side just in case the eggs will hit the side of the box. The mass of a average egg is 5.8 kg (average weight of 57kg/9.8 (gravity)) The eggs will be traveling 9.4m/s with a impact force of around "31262.98882 N"
 

Answers and Replies

  • #2
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Rubber bands have a nasty tendancy to break or perform not as expected. You could do it that way, but I think a better way (kind of cheating) would be to get a substance with a high viscoscity (jello, glycerine, peanut butter, etc) and put the egg in/on top of it. This way when it is dropped the momentum of the egg is absorbed slowly (low impulse).

The basic physics is the change in momentum or impulse. The higher the impulse (the higher rate of change of momentum) the more likely the egg is to break. [ Think about this, drop an egg on concrete, probably breaks because all the momentum of the egg is changed instantaneously by the ground. But an egg dropped into something soft (cotton?) would result in the egg slowly coming to rest, so it's impulse is much lower.

Go wild, test different designs. Test different materials/shapes etc. This problem would be very very hard to solve analytically and it was actually designed for you to test your experimental skills (Design, test, analyze what can get better, redesign, repeat)
 
  • #3
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If one is going to be serious about this, I think first he would want to know at what G force the egg breaks and even how much variation between eggs there is. Then knowing the limit of G forces the egg can withstand and the G's the box will experience on impact, it will be possible to calculate how much "give" the cushion inside the box must have.

Question for Xerxes1986: It seems to me that it is not so much the force of impact that breaks the egg but that the force on the egg is asymmetrical. If for instance, the density of gelatin were adjusted by adding more or less water, so that the egg and the gelatin were of the same density, and the egg or eggs were submerged in the gelatin, would the egg not be able to survive a greater impact force?
 
  • #4
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______________________________________________________________________
The mass of a average egg is 5.8 kg (average weight of 57kg/9.8 (gravity)) The eggs will be traveling 9.4m/s with a impact force of around "31262.98882 N"
What kind of eggs are you using?
 
  • #5
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Mass must be less the 170grams, and must be able to contain and save 12 eggs on the fall to receive max points for the contest. Happy Halloween


______________________________________________________________________

The mass of a average egg is 5.8 kg (average weight of 57kg/9.8 (gravity)) The eggs will be traveling 9.4m/s with a impact force of around "31262.98882 N"
Surely this is contradictory? That's a huge egg. :smile:

When I did a similar thing, I think we had a small tub containing the egg, filled with cotton wool, which was then placed in a larger tub filled to the brim with water, which was then wrapped in layer of newspaper. IIRC there were only 2 that succeeded in preventing the gg breaking, one of which was mine.
 
  • #6
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I like your rubber band idea. Seems plausible if done right.
 
  • #7
i would be using medium size eggs, and i would use multiple rubberbands of the thick medium size so that the force of the eggs would be dispersed over many rubberbands
 
  • #8
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Yes, very appropriate.
 
  • #10
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Force dispersion is exactly what you are after.
And rubber bands will work.
Other methods can work as well.
 
  • #11
other methods such as? ideas please
 
  • #12
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Do not dismiss your method.
 
  • #13
im not dismissing it, i am after other methods if this method will not work when i test it
 
  • #14
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I must retire for the evening, but what I will say is that your effort is in abrogating a shock wave.
Not a big deal for an egg.
Your thoughts are "spot-on" Dispersion of force.
 
  • #15
Thanks for the help, does anyone else have any input aswell?
 
  • #16
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I may not understand what you are planning but what I am picturing is one or more rubber bands attached to each inside face of the cube and the also attached by some method I can't picture to the egg.

Now if the egg is 4 cm in diameter in the small dimension, there will be (30 - 4/2)/2 = 14 cm distance for deceleration. Since the box will have accelerated from 5.45 meters at one G, the absolute minimum deceleration force will be 5.45/0.14 or about 39 Gs. How are you going to attach the rubberbands to the egg so the 39 G force will not break the egg?

If you decide to do 12 eggs instead of just one, the deceleration distance will be somewhat reduced and the impact Gs proportionately increased. I hope you have enough rubberbands. How many Gs do you think an egg can withstand?
 
  • #17
I am going to put the eggs in some sort of canister. As far as how much G's a egg can withstand i have no idea, but i do know that a egg can withstand much more if the impact is longways rather then sideways, atleast 2x the force
 
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