Forms of Energy • How do potential energy and kinetic energy differ? • How are mechanical energy and thermal energy similar? • What two forms of energy are carried by waves? Energy • Energy influences everything in your life, including the climate, the economy, and your body. • Scientists define energy as the ability to cause change. Potential Energy • Potential energy is stored energy due to the interaction between objects or particles. • Objects have potential energy if they have the potential to cause change. Objects have gravitational potential energy if they have mass and height above Earth s surface. Potential Energy (cont.) • Chemical energy is the energy stored in and released from the bonds between atoms. • Your body breaks chemical bonds in foods and converts the released energy into other forms of energy that your body can use. Potential Energy (cont.) • The energy stored in and released from the nucleus of an atom is called nuclear energy. • The Sun s energy is released through the process of nuclear fusion, during which the nuclei of atoms join together and release large amounts of energy. Kinetic Energy • Kinetic energy is energy due to motion. • An object s kinetic energy is related to the mass and the speed of the object. • The energy in an electric current is electric energy. Combined Kinetic Energy and Potential Energy The sum of the potential energy and the kinetic energy in a system is mechanical energy. mechanical from Greek mēchanē, means machine Combined Kinetic Energy and Potential Energy (cont.) • An object s thermal energy is the sum of the kinetic energy and the potential energy of the particles that make up the object. • Thermal energy of an object increases when the potential energy, the kinetic energy, or both increase. Energy Carried by Waves • A wave is a disturbance that transfers energy from one place to another without transferring matter. • Sound energy is carried by sound waves. • The energy carried by electromagnetic waves is radiant energy. Electromagnetic waves often are described by their wavelengths—the distance from one point on a wave to the nearest point just like it. Visible light is one form of radiant energy. • Objects can have potential energy (stored energy) and kinetic energy (energy due to movement). • Mechanical energy is due to largescale motions and interactions in a system. Thermal energy is due to atomic-scale motions and interactions in particles. • Two kinds of energy carried by waves are sound energy and radiant energy.