Exploring Variables While Testing & Improving Mint-Mobiles (for Elementary School)
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. As they test their “mint-mobiles” on a ramp, students investigate how forces (pushes and pulls), motion, and energy transfer affect the distance their cars travel. They measure changes in distance when mass is added, discovering patterns in how gravity, friction, and potential and kinetic energy interact. Students also practice the steps of the engineering design process by brainstorming, planning, building, testing, and improving their "mint-mobiles."
Example mint-mobiles.Copyright 2010 Denise W. Carlson, ITL Program, College of Engineering, 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 create a small model on which they perform many tests with different independent variables to optimize performance 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.
- Identify dependent and independent variables.
- Identify control variables.
- Describe how forces (gravity, friction, and pushes/pulls) affect the motion of their mint mobile.
- Explain how energy changes from potential to kinetic as the mint-mobile moves down the ramp.
- Identify and interpret patterns in data that show how mass affects motion.