What's the difference between potential and kinetic energy? Girlstart's After School participants discovered the answer to that question this week. The girls worked as automotive engineers to design and assemble their own rubber band cars. They used corrugated cardboard to cut out wheels and a body for their car. Then, they attached a wooden dowel as an axle between the wheels. Girls looped a rubber band around the axle and then wound the wheel. At this moment, the car had potential energy. It is storing up the energy of the elastic bands. When the let go of the river band, the potential energy is transferred to kinetic energy, or the energy of being in motion.