Reaction Time Ruler Set, For Measuring Acceleration Of Falling Object

Carolina is the only place I could find these. They worked well, but are basically wooden yardsticks, calibrated in milliseconds instead of length. So I was disappointed at paying about $15 per stick, whereas a similar quality wooden yardstick in a hardware store is about $1. They come with sheets for students to record results, but anyone could make up their own sheets, or simply enter results into a computer spreadsheet. There is also a useful booklet describing experiments one could do with these reaction time rulers, but I think that booklet ought to be available as a free PDF download.