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Homework Help: Egg drop and survive the fall

  1. Mar 20, 2013 #1
    1. The problem statement, all variables and given/known data
    I have to make an egg drop device. I was fishing for ideas. It needs to be the fastest time and survive the fall. If I win I get 4 points E.C..

    2. Relevant equations
    Impulse = Ft
    Position function for falling object
    s(t) = -16t^2 +Vo + So
    s'(t) = -32t
    F = ma
    p = mv
    Where p is momentum

    3. The attempt at a solution

    The equations above are just things that pop into my head that might help me solve this.
    So far I have been thinking about peanut butter in a jar or something along those lines. Maybe layers of different materials to disperse the force that the egg gets.
    This is my brain storm so far. Does anyone have any ideas??
  2. jcsd
  3. Mar 20, 2013 #2
    Maybe corn starch and water in a dilute mix. I don't know what the normal mixture is but what ends up happening to the fluid is that it solidifies when subject to stress. Depending on the mixture it could solidify so much that if you punch it not even your hand will go through it. If you make it dilute enough I could see it maybe slowing the egg while not breaking it.

    I like the peanut butter idea though, might not work though depending on how large of a drop it is. That said, how high is the drop? Do you have to design a release mechanism as well?
  4. Mar 20, 2013 #3
    It seems to me the most important piece of information is how much force/area is required to break an egg and is it the same on the end of the egg as it is for the side. Your solution occurred to me too but I thought of using gelatin mixed to the same density as the egg.
    Last edited: Mar 20, 2013
  5. Mar 20, 2013 #4
    OK guys, the drop is 14.3 meters it off a parking structure.
    I have thought more too. I like the ideas thanks. I do not have to make a release mechanism. I was thinking of a capsule type idea that could be composed of different layers The outer most could be extremely hard but absorbent material. Then the next layer could be something less...and then around the egg I would need something like the ideas you guys have generated. The gelatin, peanut butter ect......still thinking
  6. Mar 20, 2013 #5
    The reason I said the most important information is how much force/area is required to break an egg is to calculate the maximum deceleration rate of the egg when it hits the ground.

    Let's make some guesses. Suppose the minimum non-symmetrical force required to break an egg is 3.5 N/cm^2 and suppose the capsule is traveling at about 28.6 m/s when it hits the ground. You are going to have to decelerate the egg from 28.6 m/s to 0 in a distance less than half the diameter of your capsule without exceeding a non-symmetrical force of 3.5 N/cm^2. By non-symmetrical I mean that the force at one point on the egg is greater than the force on the rest of the egg. Can you calculate how large your capsule must be to do that?

    Presumably you could apply a relatively uniformly high force on all sides of the egg without it breaking. Even that would have a limitation because there is a pocket of gas in the egg.
    Last edited: Mar 20, 2013
  7. Mar 20, 2013 #6
    P.S. You specify the height in meters but your formulas are for English measurements. Serious mistakes have been made by mixing systems of measurements. You should always solve your whole problem using the same system of measurement.
  8. Mar 20, 2013 #7
    I'm going to google the the non-symmetrical force required to break an egg. I was thinking about this with my dad we were thinking to have a sort of rocket and have the cone able to crumble and absorb the impact of the drop we had the idea to start the egg the furthest away from tip of the cone. This will allow us max distance to stop the egg. We are still thinking of the idea for the inside. We were thinking of another type of tube on the inside. This is still rough.
    Please let me know any ideas that come to mind with this brain storm.
    I forgot about the measurments....not good. thanks
  9. Mar 20, 2013 #8
    Skeptic2 ,I have been googling non symmetrical force required to break an egg. It is funny it just takes me to your post on here.

    Does anyone know this ???
  10. Mar 20, 2013 #9
    I'd say your best bet will be to just start building and testing out some different materials. This sounds like an engineering project more than anything. I know this is a physics forums but I'd say worry about that stuff later. Aside from the basics, like how fast the egg will be moving when it reaches your contraption. Doing exact calculations/experimental testing on the egg is not feasible at least in my opinion.

    I think you should stick with something like the peanut butter idea. Though with a 14m drop you are probably going to need a softer fluid (less viscous) perhaps. Something like Fluff (marshmallow spread) might actually work better. Skeptics idea about the gelatin is also a really good one, you could test out different gelatin mixtures.

    I would say start by testing at a 2 meter drop, something small at first and test out a couple different types of material. Peanut butter and Fluff will probably get really expensive and annoying if you have a bunch of eggs breaking in them. For that reason gelatin or the corn starch and water might be more efficient.

    Best of luck!
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