How does a drinking straw balance work?

TL;DR

This paper investigates the unique rolling mechanism of a drinking straw balance, revealing its equilibrium states, measurement accuracy, and limitations compared to electronic scales.

Contribution

It introduces a new understanding of the straw balance's working mechanism and quantifies its measurement accuracy and limitations.

Findings

Relative errors around 22% compared to electronic scales

Minimum measurable mass is approximately 10 mg

The balance operates via rolling motion, not pivotal rotation

Abstract

We examine working mechanism of a drinking straw balance. Unlike the usual horizontal level balances which rely on the pivotal rotation, a drinking straw balance shows rolling motion. Because of this rolling and relative position between the pin and the center line of a straw, a new equilibrium state is possible after placement of a test mass. Relative errors between the measured values by a drinking straw balance and an electronic scale are order of 22%. Minimum value of a measurable mass by a straw balance is order of 10 mg.