The lesson explains the conversion of potential energy to kinetic energy, particularly when a stone is dropped from a height. The key equations discussed include potential energy (PE) as ( PE = mgh ) and kinetic energy (KE) as ( KE = frac{mv^2}{2} ). The class proceeds to calculate the potential energy and velocity of a stone with a mass of 0.5 kg dropped from a height of 11.25 meters, emphasizing the importance of using these equations to solve problems in the worksheet.