Title: Me and My Bathroom Scale
Objective: To demonstrate to students that even a bathroom scale is really a spring scale.
Standards: EALR 4 Physical Science: Big Idea: Force and Motion
Materials: a good bathroom scale.
Procedure: Step on a bathroom scale and watch the scale's surface descend. Show that
the more weight you place on this scale, the farther downward the scale's surface goes.
Pick up the scale and squeeze it to show the direct relationship between how far inward
you push its surface and the weight that it reports on its dial.
Student Questions for Inquiry:
1. What forces are acting on the bathroom scale?
2. How is gravity converted into weight?
3. Why can we create weight by squeezing the scale?
Science Behind It: The bathroom scale contains a spring that deforms as you step on the
scale. This deformation allows the spring to exert the upward support force that keeps
you from falling into the scale's surface. The scale's surface descends until the spring's
restoring force is just enough to provide its surface with an upward support force that's
equal in magnitude to your weight.