PIRA 1D50.40 Central Forces: Pail of Water, Pail of Nails
Instructions / Notes:
- Swing pail in a large vertical circle.
- The pail may be filled with nails or water.
- With nails, they can be heard dropping away and hitting the pail at
the top of the swing.
Photo Shows Demonstration as Used at the University of Texas at Austin.

Image Below is from the University of Minnesota Web-site.