  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.
