Science Buddies: "Ask an Expert"

In the Science Fair Project for the Archimedes Screw https://www.sciencebuddies.org/science- ... screw-pump the procedure lists the period as the length of the pipe divided by the number of times the tube is wrapped around the pipe. In the FAQ for "how to find the period", it lists the period as the reciprocal (# of wraps/length). Which is the correct way to find the period?

Hi - thank you for catching that! In this case the procedure is correct - the period should have units of length, so to calculate it you should divide the length of the pipe by the number of times the tube is wrapped around the pipe, which will result in units of length. We will update the FAQ accordingly.

FYI, it looks like this stems from confusing use of the word "pitch" for screws - "pitch" refers to the distance between threads on a screw (units of length), but some manufacturers list "threads per inch" as the pitch which has units of 1/length. This project uses the words "pitch" and "period" somewhat interchangeably. Ultimately, either method is fine as long as you are consistent.

-Ben