Egg Drop

As well as being a kind of chinese soup, the Egg Drop is a class of engineering contests frequently used in high school science classes, summer camps, and Science Olympiad meets. There are many variations, but all involve dropping an uncooked egg and keeping it from breaking. Here's a list of egg drop events I've participated in at Science Olympiad meets, with their rules, as I remember them. If anyone can point me to the official rules anywhere, that'd be cool:

Egg Drop

Construct a container to house and protect an uncooked egg. The container will be dropped from a certain height and judged by how close they land to a target. Any breakage or cracking of the egg automatically drops you below any teams who successfully protected their egg. You have a limited set of materials with which to construct your container (from memory):

• 10 drinking straws
• 8 popsicle sticks
• 2 rubber bands
• 2 sheets of letter-size paper
• 1 meter of masking tape
• 1 plastic grocery bag
• a few other items(?)

The scene from Apollo 13 where the aerospace engineers have to make an air filter adapter out of random NASA junk brought back flashbacks of this event. My contraption, a big spikey thing with straws sticking out all over and held together with masking tape and rubber banks, worked quite well.

Naked Egg Drop

Construct a container designed to catch and protect an egg dropped from varying heights (2-5 stories!). Some competitions are judged by the bounding cube volume of your container, others by the maximum height of the container. You can use basically any materials, although some competitions stipulate that wet or liquid materials are illegal. Obviously, it is essential that you don't miss. Hence, teams are allowed to use a plumb bob attached to a frame to position their containers, and glue a thread harness to the egg. The harness would be hung from the same hook as the plumb line, and the thread burned through to release the egg straight down.

My device was a small box filled with pieces of cellulose sponge and tissue paper, with a cardboard trap on top to keep the egg from bouncing out. It worked pretty well but wasn't as small as it could be. This event has been pretty much solved, since people have discovered certain materials can cushion an egg very well even though they are less than 1/2 inch thick. These include: hard modeling styrofoam (the real hard stuff that makes crunchy indentations, not just the stuff that is used for shipping) and alternating layers of rubber sheeting and bubble wrap. You may not believe me, but I've seen it with my own eyes. Astonishing really, that a 1/2 inch thick piece of styrofoam can cushion an egg dropped from 5 stories. Of course the egg bounces crazily; I've seen people use strips of duct tape, sticky-side up to keep it from bouncing around. At the state meet, somebody used peanut butter and would have won hands down, except that peanut butter was ruled to be a liquid and the team was disqualified.

Bungee Egg Drop

Make a harness for an egg, attached to an elastic cord. The egg is to be dropped from arbitrary heights between 10 and 50 feet, and the cord must stretch to at least 133% of it's original length. Teams should mark the cord so they can tell where to attach it from a certain height. Judging is based on how close the egg can come to the bottom, usually a pit of sand, without breaking. For teams that can touch the sand without breaking, the smallest indentation wins. Video recordings are made against a ruler behind the egg to rank those who do not touch the sand.

There are, of course, a variety of ways to drop an egg off a building, but I think that the format used in my high school was somewhat more orthodox than that described by 3Suns in his writeup (I base this on witnessing and hearing about various high school and university drops) so I will present it here for general edification:

• Any materials may be used, but no aerodynamic aids (parachutes, wings, etc.) are allowed.
• There are four rounds of increasing height. All containers that have at least one egg survive the first drop are advanced to the next round.
• No part of the container or packaging may be replaced between drops.
• Any number of eggs may be placed in a container and scoring is based on the percentage of eggs that survive. Thus a if only one egg is dropped but it survives(100%), that container will beat one in which five eggs are dropped and four survive(80%).
• In the case of a tie (very common, considering almost everyone drops only one egg), the lightest container will be declared the winner.

So, in short, the goal is to build the lightest possible container to survive four drops of increasing height, the highest of which was about 40 feet.

On a personal note, my design was to wrap one egg in one layer of soft foam wrap (the kind large electronic devices often come wrapped in), place this inside a hollowed-out cube of styrofoam, insert a number of toothpicks into the styrofoam to absorb the impact by either breaking or being driven deeper into the styrofoam (they were placed so as not to intersect the egg), and finally wrap the whole spikey thing again in soft foam wrap. This last step greatly increased the surface area and thus skirted the no-aerodynamic-aids rule, but was allowed in as it had shock-absorbing value as well. It won, was the lightest design in five years and, if memory serves, the second-lightest ever.

The lightest design ever was shockingly simple: a Tylenol box, just large enough to hold the egg, padded inside with a couple centimeters of soft styrofoam and tissue paper. It was kept by the school physics teacher and passed around with reverence each year the day after the egg drop.

The smallest container capable of protecting an egg from breaking is... an egg! So long as the drop isn’t vertical, is over 40 ft and is onto a reasonably forgiving surface, like grass, an egg will protect its own fall. At a lower height, 3-4 feet, it will almost always break.

This was the subject of much discussion in New Scientist letter pages some years ago (11 August 1960!), I think the best replies were re-published as an article because it was the most answered letter ever.

Fans of physics explained the phenomenon by studying the structural qualities of an egg.
The aerodynamics of an egg causes it to fall largest end first, in a similar way to early space re-entry capsules. If the egg isn’t dropped from high enough the egg is more likely to fall on a weaker side.

The largest end has an area of gas trapped between the egg’s two membranes. This causes the hole in the white of your hard boiled egg; it also makes peeling one easier. Upon impact the heavier spherical yolk continues moving towards the ground. The compression of the airspace acts like an air bag for the eggs’ valuable contents. It also adds additional structural support in the form of pressure to the already incredibly strong curved eggshell.

Eggs with no yolk invariably break. This is not only because the air compression wouldn’t happen properly but also because the elasticity of the chalazae which hold the yoke in place probably has some form of dampening effect on the fall.

Evolutionary theorists couldn’t help adding an explanation as well. Apparently early birds didn’t make nests. They simply laid eggs mid-flight*. The eggs which survived the fall continued to add their genetic information to their species. This theory is supported by the relatively oval shape of land based dinosaurs. In this way the existence of sophisticated physical mechanisms within a common hen egg, which certainly don’t need drop protection, are explained.

So next time you are competing against some eager MIT professors to find the best way to protect an egg from a fall, trust evolution and physics to help you win the grand prize!

Sources:

www.picotech.com/experiments/ dropping_egg/dropping_eggs.html
http://www.asl.org.au/aslnews/v37/aslnews_v37n3_articles.htm

*It has been pointed out by rootbeer277 that this is very unlikely. Most birds can’t even excrete in flight.

Update

rootbeer277 also challenged me to conduct the experiment myself. I took three eggs outside and confidently lobbed them over a tree.
The first one hit the tree and didn’t fall out. Unperturbed I lobbed the second egg. The street lights provided beautiful illumination for the resulting spray of yolk off the damp lawn.
Damn.
Remembering all my javelin training from school I hurled the last egg with all my might.
Splat.
My breakfast now lies inedible on the floor outside. I’m suing New Scientist for making me hungry.

About once every three months I get a whole lode of "Hey, sweet! Someone likes your write-up titled "Egg Drop!"" which is great because I have to assume that there is a class somewhere that has found these write-ups useful. However it would be great, particularly if you were brave enough to try my unprotected egg drop, if you would send me a private msg with your results. All you have to do is sign up to everything2 and use the box above my write-up to contact me. Thank you!