Heat engines and machines

3.1 Perpetual motion

We are sure you are familiar with the little device shown in the figure. It shows the transformation of potential energy into kinetic energy and vice versa. Can you identify these transformations?

A long cherished aspiration of mankind, which has given rise to the design of numerous devices, has in fact been to achieve a device which would convert some form of energy (electrical, thermal etc.) into kinetic energy, which in turn would be converted back into its earlier form of energy.

In this way we would obtain an endless cycle which we would call perpetual motion.

Is perpetual motion possible?

To be able to answer this question we will begin by analyzing how the device illustrated above works. You will be able to do this analysis in the following visual. We have assumed that we are dealing with only two balls of identical mass hanging from strings which are 1 m. long.

	Joule's experiment
	The first law of thermodynamics
	Conclusions