Pinewood racing - it's serious
The caller wanted to know if her son should be adding weight to the rule maximum. YES! This is a race where all the energy the car has at the start of the race is the potential energy (mass*height*gravitational acceleration constant). Since all cars start at the same height, if all else is equal (primarily wheel friction and losses due to not running straight), then the one with the highest potential energy wins. Don't focus on appearance, works the axels and wheels. Good luck to all Cub Scouts this spring as you race in the Pinewood Derby.