Low-Cost Timer to Measure the Terminal Velocity of a Magnet Falling Through a Conducting Pipe

Dropping a magnet into a conductive pipe (made up of copper or brass or aluminum) is a very popular demonstration in many physics classrooms and laboratories. In this paper we present an inexpensive timer that can be used to measure the terminal velocity of the magnet falling through a conducting pipe. The timer assembly consists of Hall effect switches connected to a digital stopwatch. The timer assembly was then used to observe the variation in the terminal velocity of the falling magnet with respect to the thickness of the copper pipes.