Exploring Variables While Testing & Improving Mint-Mobiles (for Middle School)
Mint candies aren’t just a tasty treat; they are useful in learning about science and engineering concepts! In this activity, students design, build, and test model race cars made from simple materials (lifesaver-shaped candies, plastic drinking straws, Popsicle sticks, index cards, tape) as a way to explore independent, dependent, and control variables. By investigating how added mass changes the distance traveled, students explore the relationship between force, mass, and motion, connecting their observations to Newton’s Second Law of Motion. They also examine how energy is transferred from potential energy (the raised ramp) to kinetic energy (the moving mint-mobile), and how friction and drag influence the motion of their vehicles. Throughout the activity, students practice the steps of the engineering design process—brainstorming, planning, building, testing, and improving their “mint-mobiles”—while making sense of the science behind motion and energy.
Example of a completed mint-mobile.Copyright 2020, Sabina Schill, ITL Program, College of Engineering and Applied Sciences, University of Colorado Boulder
When developing a new product or device, engineers go through many iterations of the engineering design process. First, they imagine lots of ideas and share them with their teammates. Then, the team decides on one best design and plans its final materials, specifications, functionality, and aesthetics. Before building a full-scale prototype, they often create a small model to perform tests, varying independent variables such as mass, wheel type, or shape, to see how these changes affect motion and energy transfer. By observing how forces, friction, and energy impact performance, engineers can optimize their designs for speed, stability, and efficiency while keeping cost in mind. Once a model has been refined through testing and improvement, they build it at full scale. This mirrors the scientific process, helping students understand how Newton’s laws of motion, energy transfer, and forces apply in real-world engineering.
After this activity, students should be able to:
- Explain the steps of the engineering design process.
- Define criteria and constraints for a specific design problem, considering both performance and real-world limitations.
- Identify independent and dependent variables, and control variables, in experiments involving motion and forces.
- Predict how changes in mass, force, or ramp angle will affect the motion of their mint-mobile.
- Explain how forces (push/pull), friction, and energy transfer (potential to kinetic) influence the performance of their vehicles.
- Use collected data to predict future performance of a design, justifying predictions based on principles of motion and energy.