Potential energy is the mass of an object times its height above ground. If you lift a 10 pound object 10 feet it has a potential energy of 100 pound-feet. The energy is released when it returns to the earth. Another form of energy is kinetic energy. This is possessed by an object in motion and is equal to 1/2 the Mass time the Velocity-squared (1/2MV^2). There is also energy related to electricity and magnetism and temperature as will as Einsteins famous equation E= MC^2 which is the energy produced by an atomic reaction where E is the energy, M is the Mass converted to energy, and C is the speed of light in a vacume,and straw rockets are an example of potential energy.