Egg Drop Challenge
Saturday, April 18, 2015
Free with Museum Admission
Originality and creativity are appreciated, but your design needs to follow these guidelines:
- Design cannot involve liquids, helium, other lighter-than-air gasses, or glass.
- Weight cannot exceed one pound.
- Egg "compartment" cannot exceed one foot in length or width. Winged designs need to fall within this dimension.
- You must be able to place your egg into your container just prior to your drop. Montshire will provide each entry with a grade A, fully inspected chicken egg!
- Use of parachutes is allowed, but the chute must deploy itself after the container is dropped. Dropping with an open parachute will almost certainly result in successful landing. Using other methods within the guidelines presented here will make for a more interesting challenge.
Your Egg-citing Challenge
The goal of this challenge is to have a raw chicken egg fall approximately six meters onto a hard surface and survive the impact uncracked. Let's look at the elements of the problem.
- Eggshells are remarkably strong. If you hold an egg in the palm of your hand and try to crush it by wrapping your fingers around it and squeezing, you will find that it takes a large force to crack the shell. However, the shell can be broken rather easily by hitting a small area with a hard object. Therefore, you need to protect your egg from very large forces applied all over and from moderate forces applied to small areas of contact.
- Falling objects are pulled toward the earth by the force of gravity. The farther they fall, the faster they will be going when they stop. When an egg reaches the floor after a six-meter drop it will be going at about 11 meters (36 feet) per second and will be stopped very suddenly when it hits the floor (this is called the impact). Its speed when it hits the floor is about 37 kilometers (24 miles) per hour.
- An unprotected egg falling six meters onto a hard surface will encounter the worst situation—a very large force applied to the small area where the egg first contacts the floor. The large force arises because the egg is going fast and because it is stopped suddenly. The egg will break!
- An additional factor is the mass of the egg and its package. This plays a role, since the mass of the falling object affects the impact force. By requiring that all entries use chicken eggs, we can assure that the mass of each egg is essentially the same. That is why other kinds of eggs are not allowed. But the packaging material adds mass, and that must be a consideration when the package is designed. The two things you can do to reduce the force on the egg are to slow the egg down and lengthen the time of impact. You can design a package that will do either or both of these things.
- Slowing the egg down as it falls can be accomplished by using a parachute, wings, or similar device that relies on the resistance of air. As a parachute expands during descent, more air is trapped and resistance increases. Therefore the construction of the parachute is important. Wings slow descent by increasing the friction of air on the surface of the wings. Wings also affect the direction of fall, and should be designed to allow the egg to fall vertically. Will the size of the parachute affect the rate of fall? What materials are best for parachutes? Will the size of wings affect the fall? Is the position of the wings important? Why? Do you think it is possible to construct a parachute that is so effective in slowing the descent of the egg that the egg would not have to be protected?
- The faster the descent of the egg, the more important the packing around the egg. An egg in free fall (no parachute or wings) needs more effective packing than an egg with a parachute.
- Soft, crushable packing that encloses a lot of air is best. Foam rubber, feathers, cotton or synthetic batting are all good "cushioners." Think of other materials that are soft and yielding, and incorporate air (stiffly beaten egg whites, milkweed fluff, etc.). What soft, fluffy materials could be tried? How can you minimize the mass of the package?
- A word of caution—water and other liquids are not permitted under the rules of the contest. And liquids do not make good "cushioners." It is true that water distributes the impact force over the total surface of the egg, but water adds mass. This increases the stopping force considerably. Since water is virtually incompressible, the egg stops abruptly and is unlikely to survive. The use of Jell-o involves similar problems and is not recommended. Could you find a way to incorporate air into Jell-O? Do you think that would make it a good cushioning material?