To illustrate the conversion of gravitational potential energy into kinetic energy and then into work.
Pile driver shaft, cylindrical iron weight, wood block with nail and hammer.
Start a nail into the center of the wood block. Place the block on the floor with the nail up and position the pile driver tube over the block. Hold the iron weight at the top of the tube and release it. The weight will fall to the bottom and pound the nail into the wood.
Julius Sumner Miller, Observations on a Pile Driver, AJP 22, 409 (1954).