Roller Coaster Design - Day 2
Lesson 8 of 16
Objective: Students design their own roller coasters and calculate important aspects of the ride like velocities, work and power of the motor, and braking force.
This is a double-period so the total time is 100 minutes. Most of the groups need this time to finish their roller coasters and present their designs to me for immediate feedback and grading.
This task, started the day before, combines the many concepts in energy (conservation, kinetic and potential energy, work and power) and asks students to design their own roller coaster. They must calculate the total energy of the roller coaster, determine the velocity at various points and make sure that the coaster makes it around at least one circular loop.
The only way to accomplish this task is to apply NGSS engineering practice HS-ETS1-2: Design a solution to a complex real-world problem by breaking it down into smaller, more manageable problems that can be solved through engineering. As they work through their designs, students use Science Practice 1: Asking questions (for science) and defining problems (for engineering). Students have to use a mathematical model of energy conservation which applies Science Practice 2: Developing and using models and Science Practice 5: Using mathematics and computational thinking throughout the process.
To ensure their designs are safe, students show that this is the case with calculations and conceptual understanding, which involves NGSS Science Practice 7: Engaging in argument from evidence. All of this is in the context of NGSS performance standard HS-PS3-3: Design, build, and refine a device that works within given constraints to convert one form of energy into another form of energy.
While students are working on their roller coaster, I circulate the classroom and give support where needed. At this point, most groups have worked out a theme and completed the design phase of their roller coasters. They work on the calculations needed to determine the velocities at important points. Most groups measure the height to first figure out the potential energy and then subtract that from the total energy to get the kinetic energy. Once they have the kinetic energy, they can solve for the velocity.
The points where they must determine the velocity are at the lowest point of their track where the velocity is the greatest and at the top of their loops. Students must apply the centripetal acceleration equation (a=v^2/r) at the top of the loops to make sure that the centripetal acceleration is greater than acceleration due to gravity otherwise people could fall out of the coaster. This is a topic that was learned in Design Your Rotating Space Ship so students are familiar with this process.
In order to better serve the students who need my help, I have devised a three cup system that alerts me to who needs help. At each table are three cups, a red one, a yellow one and a red one (pictured right). Depending on how students are doing in the assignment, they will put one of the colored cups on top.
Green Cup: Default cup, everything is going well, we don't need help.
Yellow Cup: We are struggling with a concept, we need you to affirm that we are heading in the right direction.
Red Cup: Help! We are totally stuck and can't move forward.
As students work through the assignment, I scan the room. Red cups get priority and then yellow cups. The cups are a permanent fixture at the tables and are used when ever students are engaged in student centered activities (worksheet, laboratory, inquiry, etc). If I look up and see mostly green cups, then I know things are proceeding well. However, if mostly red cups are displayed, then this tells me that I have to stop the independent work and reteach teach the concepts.
When students finish their project, I have them grade their project using the Roller coaster rubric, which they received when the project was first assigned. This exercise of self-assessment usually results in students finding some of their own mistakes or missing pieces.
When students are confident they are ready for my grading, they bring up their project and rubric with their self-grading on it. I talk through the rubric as I grade their project with them standing there; I ask questions and make observations. After the grading is complete, I give the group the option to turn in their project as is or to fix any of the mistakes. This allows them the opportunity to improve their project.
Once a group turns in their assignment, I give each student the Sankey diagram homework to begin so that they have something to do while the rest of the class finishes their projects. This assignment requires a computer and internet access and asks students to research the concept of a Sankey diagram and to find an example of one. Computers are available for students to use in the classroom, but most prefer to use their smart phones.