# Build an Interplanetary Scale

UNCG Author/Contributor (non-UNCG co-authors, if there are any, appear on document)
Catherine E. Matthews, Professor (Creator)
Institution
The University of North Carolina at Greensboro (UNCG )
Web Site: http://library.uncg.edu/

Abstract: Help your students understand mass, weight, and gravitational fields with an interplanetary scale. Students can simulate their weight on any planet or satellite with a surface gravitational field equal to or less than Earth's. This includes Earth's moon and all other planets in our solar system except Jupiter, Saturn and Neptune. In this activity, students use a bathroom scale and a long board to see how their weight changes on other planets and the Moon. Standing on the end of the board with the scale, students see their Earth weight. As the student moves down the board, away from the scale, their weight is redistributed between the two points of support in a proportional manner. When the student stands on the board right above the scale, their Earth weight is shown. At the halfway point on the board, the scale reads one-half of their Earth weight. If they stand at the other end of the board, away from the scale, no weight is supported by the scale, representing zero gravity. Using the gravitational ratios of the planets, computed using each planet's mass and radius, students can calculate where on the board they need to stand to replicate their weight on another planet and the Moon. Divide the weight in pounds by 2.2 pounds per kilogram to get the weight in kilograms.