1-30-09

On Friday January 30, 2009 Mr. Manning was absent from school. The substitute showed the class a video on Work and Energy. There are a number of key points that should be mentioned pertaining to the video. The video made it very clear that energy is always conserved in the environment. In other words the amount of energy in the universe is always the same, and it can not be created or destroyed. The video explained how to calculate the amount of work done when lifting an object. The equation is the same as the one for the gravitational potential energy of an object (U = mgh) where U is the gravitational potential energy, //m// is the mass, //g// is gravity, and //h// is the altitude (or height). An object's potential energy is directly proportional to its height above the earth; the work done on an object is identical to the potential energy it receives. Work may cause a change in height or speed or both. The video also mentions the term mechanical energy. Mechanical energy describes the potential and kinetic energy present in the components of a mechanical system. It can be found by adding up the kinetic and potential energies in a system. When an object stops moving, its energy is not lost but instead turns into heat and sound. While heat and sound are still energies (they cannot be created or destroyed) it has minimal entropy, or a measure of how useless a certain form of energy is.) Energy is the scalar physical quantity that describes the amount of work that can be performed by a force. * This typical starting device for an engine converts electric energy into mechanical energy to get it started.