An interesting, quick, and inexpensive lab that we do with our students is to tape one end of a string just less than halfway around the back side of a uniform solid cylinder m[subscript 1] and attach the other end of the string to a mass m[subscript 2] that is below a pulley (Fig. 1). Data can be collected using either an Ultra Pulley (Fig. 2) or a motion detector with a protective cage designed to stop the falling mass (Fig. 3). We found that each measuring device worked equally well. When experimenting, let m[subscript 2] hang freely and release the cylinder. The mass m[subscript 2] is allowed to fall a defined distance h. Note that many motion detectors do not measure accurately within 15 cm of the detector. (Contains 6 figures.)