Cup Balance

A simple design that uses standard 3.5 ounce plastic cups and a toothpick to measure relative masses.

The toothpick must be round and is a fairly snug fit in the hole on the top but can be easily replaced if it breaks. The supports can be anything that provides clearance for the cups without interfering. As shown in the photo, I just use upside-down large plastic cups

This can used as part of a lab where students use beans as units to quantify a variety of properties including mass.