Teaching Engineering Design with an Egg Drop

Background Information for Teachers

This lesson is designed to guide your students through the engineering design process (Figure 1) using a classic hands-on activity: an egg drop. You can read about the engineering design process, or assign your students to read about it, in much more detail in this project guide. You can also read about the differences between the engineering design process and the scientific method.

Image Credit: created by Amy Cowen for Science Buddies / Science Buddies

A flow chart shows the engineering design process. The process begins by defining a problem and completing background research on the problem. Requirements are specified and a solution is chosen. A prototype of the solution is built and tested. If the prototype / solution meets the requirements then the results can be shared. If the solution does not meet all the requirements then another solution is developed and tested. Each iteration uses data from previous tests to meet all of the initial requirements.

Figure 1. Steps of the engineering design process.

Your students will use readily available materials to build a device that can protect an egg during a fall. Egg drop contests frequently reward students whose eggs survive drops from the highest height. Students might only get one chance—if your egg breaks, you are done. This version of the project is intended to emphasize the iterative nature of the engineering design process. Students will be allowed to test their designs before they try them with a real egg. This will give them a chance to identify flaws and improve their designs.

Optionally, this project can be linked to several other physics topics:

• Energy/Energy Conversion/Conservation of Energy: when you raise the egg drop device off the ground, it gains gravitational potential energy (usually just called "potential energy" for short, when "gravitational" is implied by the context). When you drop your device, it falls and gains speed. The potential energy converts to kinetic energy, but the total amount of energy is conserved. When the device hits the ground, all that energy needs to go somewhere. It can be "absorbed" by the device and converted into elastic potential energy (e.g. stretching a rubber band), it can be converted into heat or sound, or it can go into breaking molecular bonds in the materials of your device (or the egg, which is what you want to avoid!). You want to design a device that can safely absorb/dissipate all the kinetic energy on impact without breaking the egg.
• Newton's laws of motion: when your device hits the ground, it experiences a very large change in velocity in a very short period of time. This means it has a very large acceleration (acceleration = change in velocity / change in time). According to Newton's second law of motion, Force = mass × acceleration (F=ma), so if there is a very large acceleration, there must be a very large force. If you can decrease the egg's acceleration (e.g. by adding a parachute so its velocity is not as high to begin with, or adding cushioning so it does not come to a stop as quickly), you will decrease the force on the egg, making it less likely to break. You can also think in terms of Newton's third law of motion: for every reaction, there is an equal and opposite reaction. When the egg hits the ground, it pushes on the ground—but the ground also pushes back up on the egg.
• Pressure: pressure is force per unit area. If you apply the same force over a larger area, the force is more "spread out," and the pressure will decrease. Imagine standing tiptoe vs. standing flat on your feet. The total force (your weight) is the same in each case, but when you stand on your toes, the contact area with the ground is much smaller, so the pressure is higher. Now think about the same concept with an egg. Are you more likely to break through an egg shell if you press down on it with the entire palm of your hand, or if you press with the same force using a needle? In the latter case, the same force is concentrated on a very small area (the tip of the needle), which is more likely to break the egg. Students can use this knowledge to design a device that evenly distributes the impact force across the surface of the egg, making it less likely to crack.

Additional Background Links

• The Engineering Design Process, Science Buddies
• Comparing the Engineering Design Process and the Scientific Method, Science Buddies
• Newton's Laws, The Physics Classroom

Prep Work (30 minutes)

1. Recommended: build an egg drop device yourself and test it at the same location you plan to use with students. This will give you a rough idea of the number of drops your students' devices should be able to survive. For example, a well-built device may easily survive 10 or more drops from a relatively low height (from standing on a chair or picnic table), but may only survive two or three drops from the top of the stadium bleachers.
2. Review the engineering design process steps for this project (see Explore section) and decide how much time you will allow for each step. Some steps (e.g. background research) could be assigned as homework.
3. Develop a set of rules that all students must follow. You can adjust the rules based on the time and materials you have available, but here are some suggestions to get you started:
   1. Materials: students can only use the materials you provide in the classroom.
   2. Size limits: the device must fit inside a 1×1×1 foot cube.
   3. Egg accessibility: you must be able to easily access the egg to check if it is broken (i.e. you cannot permanently wrap the egg in duct tape).
   4. Test drops: during testing, students can use a dummy egg (see Materials list). They are allowed to make modifications or repairs to their design (including using new materials) during testing. Place a time limit on the testing period (e.g. 45 minutes), after which students must have their final design ready.
   5. Official drops: official drops must be done with a real egg. Students are not allowed to make repairs or modifications between official drops. Students will repeatedly drop from the same height until the egg breaks. Make sure you notify students of the official drop height/location.
4. Optional: you can develop a scoring method to determine a winner. This could simply be the device that survives the most drops. In the event of a tie, you could use the device weight as a tiebreaker (lighter device wins). Alternatively, you could score all devices using the number of successful drops divided by the weight, so a very lightweight device that survives fewer drops has a chance of beating a heavier device that survives more drops. This can be connected to real engineering practices (things that use fewer materials are generally cheaper) and/or the spacecraft analogy mentioned in the Engage section (launching heavy things into space requires a lot of energy, so spacecraft need to be lightweight).
5. Based on your decisions above, make a rules document that you will provide to the students. You can use this editable rules document as a starting point.

Engage (10 minutes)

Tell your students that they will be doing an egg drop project with the goal of building a device that can protect an egg from breaking when dropped from a certain height. The objective is not to survive a single drop from the highest height, but to survive as many repeated drops as possible from the same height.* They will follow the engineering design process as they design, build, and test their devices. This process is different from the scientific method. Real-world engineers and inventors use it when they design new products. Pass out copies of the rules document (see Prep Work section) and student worksheet to each group of students.

*Optional: there are several ways you could connect this lesson to current events and recent technological developments. You could discuss how space companies like SpaceX are working on developing reusable rockets that can launch into space and then land on Earth safely. In the future we might want reusable landing craft to carry astronauts to the Moon or Mars. So, their goal is to build a reusable spacecraft that can protect their "eggstronaut" during landings. Alternatively, companies like Amazon want to deliver packages using drones—but what if the drone crashes or the package gets dropped? Will fragile contents be safe?

Explore (2-3 hours)

Guide your class through the engineering design process using the worksheets to document students' work. Remember that you may choose to assign some of these steps as homework instead of doing them in class.

1. Define the problem. This step is a little different because the main problem to tackle (a successful egg drop) is already selected for students in this lesson. While it may seem obvious, students should make sure they understand what the problem is and why they are trying to solve it (i.e., what happens if you just drop an egg onto a hard surface? Why is that bad?). They should also understand what exactly they are trying to do (i.e. surviving repeated drops vs. surviving a single high drop). The scenarios mentioned in the Engage section can also be used in this step.
2. Do background research. With an engineering project, there is no need to start from scratch when a lot of other good ideas and information are already out there; nothing is wrong with using someone else's design for inspiration. What are some examples of other successful egg drop projects in the past? What about other devices designed to protect fragile things when they crash? Helmets? Air bags? Parachutes? How do they work? What are they made of?
3. Specify requirements. This is where you will find out if the students paid attention to your explanation and their rules document. What does their egg drop device need to accomplish? What limitations (e.g. time and materials, other rules) do they have to work with?
4. Brainstorm solutions. This is an important step, especially for teamwork. One student might come up with a single favorite idea right away, and insist on using that idea. It is important for everyone in the group to participate in brainstorming multiple designs. The best design might not be obvious right away, or it might be a combination of several different designs. Encourage each student to brainstorm and sketch at least three different designs, list what materials they will be made of, and explain how the design will work. Then, group members should share their design ideas with each other. Listen carefully and respectfully to everyone's ideas before providing feedback. Avoid harsh responses like "That will never work!" Instead, provide constructive criticism like "I am worried that idea will not work because I think this part will break." If students struggle with this brainstorming step, consider using SCAMPER as a tool to get creativity flowing.
5. Choose a design. Now the hard part: the team will need to agree on a single design to build and test (remember that it can be a combination or modification of their initial designs). They should carefully evaluate all their ideas to determine which one will solve the problem and meet all the requirements the best. Optionally, they can use a decision matrix to make this process more quantitative and less subjective.
6. Build a prototype. Once the group has decided on a design, they should build a prototype using the materials supplied. The iteration process may begin early if they discover that their design "on paper" does not work when they try to build it in real life. Maybe two pieces do not fit together like they expected, or the materials they chose are not suitable. That is OK! If they discover a problem as they are building their prototype, the group should discuss what changes they need to make to the design.
7. Test and redesign. When students are finished building their prototype, they should test it. It is a good idea to test incrementally instead of immediately going for the full height with a real egg. For example, first try dropping the device from waist height with no egg at all. This may allow you to identify any major flaws or unforeseen problems with the design. Then, try dropping from increasing heights (e.g. holding it over your head, standing on a chair...) using a dummy egg. After each drop, check the device for damage. Does it have weak spots? Are the materials behaving as you expected? What could you change to make it stronger?
8. Final Testing: all groups should put a real egg in their device and bring it to the drop location. Cycle through the groups: everyone drops their device once and checks if the egg is broken. All surviving eggs are dropped a second time, and so on, until all the eggs are broken. Record the number of successful drops for each group.

Reflect (20 minutes)

As a class, discuss the engineering design process and the results of the project:

• What designs did people think of initially? Did anyone have similar ideas during the brainstorming process? Did anyone have a totally unique idea that no one else came up with?
• What problems did people encounter during the design and prototype-building process? Did everyone's design work exactly like you thought it would on the first try? Why or why not?
• What did you discover during the testing and redesign process? What changes did you make to your designs? Why?
• What were the results of the final testing?
• Which devices survived the most drops? Did they have anything in common?

Assess

In addition to assessing the student worksheets, you can ask each group to prepare an oral presentation, written report, or poster about their design process.

Make Career Connections

Discussing or reading about these careers can help students make important connections between the in-class lesson and STEM job opportunities in the real world.

Mechanical Engineer

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Career Profile

Mechanical engineers design many machines and vehicles that ideally are not supposed to crash. But if they do, they need to keep their fragile occupants (people!) safe. Engineers go through a similar testing process where they design, build, test (and crash!) prototypes of vehicles before real people are allowed to ride in them. Read more

Lesson Plan Variations

• There are many ways you can modify the format of an egg drop project to make it a competition or add scoring. See the Prep Work section for suggestions.
• You can connect an egg drop project to real-world engineering challenges like a Mars landing craft or drone package delivery. See the Engage section.