The goal of this lesson is to help students use research and design to construct explanations and design a solution to an engineering problem using concepts that relate to momentum and its conservation. I want students to apply the idea that momentum is conserved when the net external force acting on a system is zero. In the case of a freefalling object, momentum is not conserved because the net external force is the force due to gravity. This lesson addresses the HS-PS2-3 standard because it asks students to leverage their understanding of forces and momentum to create a device that protects an extra large grade A egg from breakage during free fall from a known height. It aligns with the NGSS Practices of Asking Question (SP2), Planning and Carrying Out Investigations (SP3), Constructing Explanations (SP6), and Obtaining, Evaluating and Communicating Information (SP8) for Science because students use their prior knowledge of momentum, free fall and design to construct a device within a set of constraints to protect an egg dropped from a fixed height.
Within this lesson, students constructing an explanation of the key terms that relate to an object's momentum. Students collaborate to design and build a device that protects an egg during free fall using their understanding of momentum. Students then test their prototypes to compare the theoretical and experimental values for final velocity and time of flight. Finally, students create headlines that correspond to today's lesson. Within this lesson, I ask students to focus on deepening their current understanding of momentum. I assess student understanding throughout the lesson using informal check-ins, and assess each student's work at the end of the school day. I want students to learn to integrate information from various points of this course into a coherent project. I ask students to look for and take note of more direct connections between the factors from this week's lessons and the presentation they are constructing during the next few lessons. Instead of a traditional bell-ringer, I present students with a set of rules for a design challenge. During this design challenge, student work in pairs to use their knowledge of momentum and forces to prevent an egg from breaking after falling between the second and ground floors of our school building.
During this section, I spend the first few minutes distributing a handout with the criteria for the Egg Drop project. While students spend five minutes reading the handout and choosing partners, I circulate and address any puzzles students may have. This part of the lesson has students create a plan for building a device that will prevent an egg from breaking within the following constraints and requirements:
Students spend about ten minutes crafting a plan of action on how to go about creating the device and conducting research to meet the requirements from the handout. Typically student game plans include:
Students use their game plans to keep track of project requirements. Students must build a device within these constraints and communicate a set of required information including the time of flight, the average force of impact and a sketch of student-designed devices. As students complete their projects, their focus will be on the NGSS Cross-Cutting Concept of Systems and Models while they illustrate their understanding of momentum conservation to create a prototype to protect an egg from shattering upon impact after it free falls from the top of the second floor stairwell to the ground floor.
I introduce this section of the lesson by asking students to spend five minutes writing everything that comes to mind when the hear the word "engineering" in their laboratory notebooks. After five minutes pass, we have a five minute whole class discussion about student ideas on engineering. Student responses included: "Building", "Solving Problems", "Uses lots of math and physics", "Requires sifting through a lot of information", and "Cool Job". I remind students that communicating information in an easy to understand way, like creating detailed sketches drawn to scale like an engineer would, is an essential skill for scientists.
Then I ask students to spend the next thirty minutes work in pairs to create a device that can hold a single raw hen's egg and protect it when dropped from the 2nd floor of a building. The front resource station holds equipment in labeled drawers or containers and includes scissors, rulers, meter sticks, washers, colored pencils, markers, dry erase markers, string, whiteboards, multiple sized unlined paper, and highlighters. I project the requirements for student projects on the interactive whiteboard at the front of the room. Each momentum and collision engineering design project must include:
Some students split up the work and one team member creates prototypes while the other partner conducts research. Other teams work in tandem using Chromebooks to conduct research using a shared google document. While students work on this project, I circulate and check-in with student teams about their designs. Click here to see an example of student work. Students test their prototypes the following day when we meet at the end of the school day.
At the end of this section, I pause and ask students to label their exhibit components and return the materials they used during this section to the front resource station. A resource manager returns each material to a bin or labeled drawer so that they are readily available the next time the materials are needed.
The closure activity asks students to identify and describe their personal level of understanding of key ideas within the lesson. The writing prompt asks students, "If you were to write a headline for this topic or issue right now that captured the most important aspect that should be remembered, what would that headline be?" Students write their responses either in their notebooks on or our Edmodo wall. I like this activity because students identify and share the portions of the lesson they feel are important and challenging as headlines. Student responses include: "You need to understand that momentum is conserved to create a working prototype to keep an egg from breaking" and "Gravity is the only force acting during free fall, so if you need to understand free fall to keep your egg from breaking".
To wrap up this section of the lesson, I ask students to look at this tutorial and practice questions that I post on the class Edmodo wall for homework. I check student responses to this closure to determine whether students are proficient in the understanding of the connection between scenario descriptions and the design project from this lesson.