Class started with a check of answers to homework questions.Demonstrations of stretched rubber bands, textbooks lifted and dropped on pretzels, and clocks wound by hand were used to show that work was done and in each example, the band, book and spring had the ability to do work. This ability is called energy and measured in joules. The concentration of the lesson was on mechanical energy, the energy of position. The first form of ME was defined as potential energy (PE), which is "stored energy". The examples being elastic PE, chemical PE, and gravitational PE. Explanations of the 3 were given.