The looped end of the string is pulled down with a force probe or a spring scale. As the string is pulled with the spring scale the disc rotates. At every mark of the disc the student will record the pulling force. The sum of the total distance times the average force is equal to the starting energy. All Wound Up from his book.
Students measure the starting energy and the spring constant for their mouse trap's spring.
Once you know the spring constant and starting energy students can make predictions about total travel distance, and calculate such variables as power, rolling friction, and efficiency. This activity takes students through the collection of data and the the formulas for each calculation. This is one great game. The split-second stopwatch game where players try to estimate time to win. The action is non-stop and players play on every role of the dice.