Presents the computer microworlds developed by the Children's Construction of Rational Numbers of Arithmetic (Fractions) Project. Provides an overview of three microworlds: Toys; Sticks; and Candybars. Discusses how children are expected to use the microworlds to construct an understanding of rational numbers. (MDH)

Described is the use of computer software, with and without guiding text, for a simulation that presents processes related to electric charges and electric forces underlying the electric-pendulum phenomenon. Included are methods for integrating this simulation with actual middle-school science class demonstration. (JJK)