Egg Drop: Air Resistance

 
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Think like an engineer and get creative with design in class.

You know the basic rule: what goes up must come down, and a tossed egg is a mess waiting to happen. The egg drop is a classic science experiment, but it can still be pretty intimidating if you’ve never successfully completed it. To drop an egg without breaking it, you need to find a way to minimize the force of the impact and its effects on the delicate egg shell. The best ways to do this are to cushion the egg while also changing the way it drops and the way it lands. By adjusting the mass of your egg and its distance to the floor, you can give your egg a fighting chance to survive the crushing grip of gravity.

In this project, you design a safety harness that can prevent an egg from breaking when dropped. “Design thinking” skills can be developed while students learn and apply basic concepts about physics and motion. Students should think critically about the forces their egg will experience, how much force it can withstand, and how to create a vessel that will absorb or diminish the forces on the egg. Students begin by formulating and answering some key questions and then use Autodesk 123D alongside laser cutting to create a prototype of their 3D design.

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Project Brief: Egg Drop

It’s all about the tools and the process!

“Design thinking” skills can be developed while students learn and apply basic concepts about physics and motion. Students should think critically about the forces their egg will experience, how much force it can withstand, and how to create a vessel that will absorb or diminish the forces on the egg. Students begin by formulating and answering some key questions:

• What are the most significant forces that will act upon the egg?
• What materials will your egg drop container be made from?
• What math and equations will inform your egg drop design?
• Where will the force of the fall be directed?
• What features of the design add or reduce air resistance?
• What similar solutions from the real world can be used to inform your design?

Process:
For this egg drop project, the first task is to develop basic skills in using Autodesk® 123D Design® software to develop concepts as part of the Design Thinking ideation stage. After completing the sample egg drop protector, students are encouraged to develop their own designs and apply their knowledge of the software and the fundamental physics to generate multiple concepts for alternative designs. The bottom line is this: if students can expand and enhance their ability to combine the innovation capabilities of the software, the power of the design thinking process, and critical thinking skills about engineering and physics, then the goals of this curriculum have been achieved.

Design considerations used in the example project are as follows:

• Purpose: Does the egg drop protector achieve the basic goal of allowing the egg to survive a fall?
• Design: What does the egg protector look like? How do the design features function? How is the egg loaded or unloaded?
• Physics: What forces act upon the egg and need to be mitigated by the design?
• Creation and assembly: How will the components be made? How will they be assembled to create the final product?
• Scheduling requirements: 5 to 6 hours

In this course, you will demonstrate knowledge of the following concepts:
• Gravity is an attractive force that exists between two or more bodies of mass, and is relative to the mass of the bodies and their distance to one another. In practice we are usually concerned about the gravitational force exerted by the Earth due to its mass and its close proximity, but it is worth noting that other large bodies of mass can exert measurable gravitational forces, such as the sun and moon. If the distance between an object and the center of the earth is considered constant (as the difference is negligible in most cases), then the gravitational force (Fg) exerted by the Earth on an object is equal to the objects mass multiplied by the acceleration of gravity (g), which is a constant 9.8 meters per second per second. The force of gravity (Fg) is also known as an object’s weight.
• An object is in free fall if the only force acting on it is the force of gravity. This situation is very rare, as it implies that there is no air resistance. If an object is truly in free fall on the surface of the earth, its acceleration will be 9.8 meters per second per second.
• Air resistance, or drag, is a force that resists the movement of an object while traveling through a fluid, such as air. Much like friction, it is caused by the exterior surface of a moving object in contact with air. Actually calculating the air resistance of an object is very difficult, as it is dependent on the shape, velocity, and surface finish of an object, as well as the density of the air, wind speed, and the humidity. In general the larger the cross-sectional area and the higher the velocity, the greater the air resistance will be.
• Terminal velocity is the velocity of a falling object when its drag (air resistance) equals the force of gravity, at which point a falling object will travel at a constant velocity. Terminal velocity can be used as an indicator of how aerodynamic shapes of similar weights are. For example, a feather’s terminal velocity is much lower than that of a similarly weighted bean.
• Momentum is defined as the product of a body’s velocity and its mass (momentum = velocity*mass). Momentum is a conserved quality; in other words, in any closed system the sum of all momentum stays constant. When determining the outcome of collisions, this quality is particularly useful when coupled with kinetic energy.
• Pressure is defined as a force applied to an area.

• Rapid prototyping technologies that include laser cutting and 3D printing enable students to produce physical prototypes for engineering and scientific inquiries. These physical artifacts offer students the opportunity to test ideas as a way to deepen their understanding of discipline-specific content.
• Software such as 123D Design enables students to translate conceptual ideas into virtual prototypes to support understanding of science and engineering concepts.

As a result of participating in this project, students will be able to:

• Describe the dynamic relationship among materials, structures, and the forces that impact them.
• Describe how gravitational forces affect a falling object, and understand the formula F = M A.
• Demonstrate skills in using Autodesk 123D Design software to generate multiple concepts for a light-weight structure that will protect a fragile egg from breaking upon impact with the ground.
• Demonstrate skills in using 123D Make software to generate templates for a structure built from interlocked sections of corrugated cardboard.
• Describe how laser cutting technology can be used to rapidly prototype a design generated in 123D Make.
• Demonstrate skills related to incorporating virtual and physical representations of applied science explorations into a variety of presentation formats that can include written essays, and oral and visual presentations.
• Demonstrate competence in effectively utilizing digital media.