Pigs can"t really fly, this one hangs from the ceiling from a string. I was lucky to buy the pigs very cheaply but you can use any similar flying toy. The pigs travel quite fast in a fairly big circle so you will need a fair bit of space and some long rulers. The time period is simply measured with a stop watch. In my experience students aren"t very good with knots so I tied them all up using a slip not to make changing...