Exploring Variables While Testing & Improving Mint-Mobiles (for High School)
An example of a mint-mobile.Copyright 2020, Sabina Schill, ITL Program, College of Engineering and Applied Sciences, University of Colorado Boulder
What can round mint candies and coins teach us about engineering? More than you might think, particularly when it comes to understanding and testing dependent and independent variables! In this activity, students design, build, and test model race cars using simple materials, including lifesaver-shaped candies, plastic drinking straws, Popsicle sticks, index cards, and tape. Working within a budget, students explore trade-offs among performance, safety, materials, and cost, applying the engineering design process by brainstorming, planning, building, testing, and improving their "mint-mobiles."
Students then investigate how changes in the mass of their mint-mobiles affect performance. By systematically varying mass and measuring resulting distances traveled, students gain hands-on experience with independent and dependent variables, control conditions, and the iterative nature of engineering design. This activity encourages students to apply principles of physics, such as Newton’s laws and energy transfer, while making evidence-based predictions and optimizations to improve their designs.
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. The team then decides on one best design and plans its final materials, specifications, functionality and aesthetics. Before building a full-scale prototype, they create a small model on which they perform many tests. This process often involves balancing tradeoffs between optimized performance, safety, and cost. Once a model has been perfected, they build at full scale.
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.
- Defend design choices considering tradeoffs.
- Describe how Newton’s Laws of Motion apply to their mint-mobile’s movement, including the effects of mass, force, and acceleration.
- Explain the role of energy transfer (potential to kinetic) and friction in determining the distance a mint-mobile travels.
- Analyze real-world data by determining the equation of a line of best fit and use it to predict performance under different conditions.