Measuring Viscosity with A Damped Harmonic Oscillator

The damped harmonic oscillator is a staple of undergraduate physics education, and the Stokes’ Law drag is often used as an example of such damping. This force has the required form of F = -bv; however, the coefficient b is dependent on the fluid viscosity, which is itself a function of the fluid’s temperature. We attached a spherical mass to the end of spring that was suspended in the liquid; the other end of the spring was attached to a force sensor. After slightly displacing the mass, we used Pasco software to record the Hooke’s Law force during the motion. A graph of force versus time yields the damping coefficient, from which we could measure the fluid’s viscosity. By comparing the viscosity to a table of known values, we could then determine the fluid’s temperature.