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Energy How Work Gets Done
What is Energy? Energyis the ability to cause change
Two General Types of Energy • Potential Energy • Kinetic Energy
What is Potential Energy? • Potential energy is the energy stored in an object. • Examples: • Chemical energy stored in batteries. • Mechanical energy stored in a compressed spring, or tight rubber band.
Gravitational Potential Energy • Gravitational potential energy is the stored energy of position. • A rock on top of a hill has more potential energy than the same rock at the bottom of the hill because the rock at the top has the added energy of being in a position where gravity can act on it longer. Weight (N) = mass (kg) x gravity (9.8 m/sec/sec) GPE = weight (N) x height (m)
Kinetic Energy • Kinetic energy is the energy of motion. • The faster something is moving the more kinetic energy it has. • KE =(m x v2) / 2
Forms of Energy • Mechanical Energy • Sound Energy • Chemical Energy • Thermal “Heat” Energy • Electromagnetic Energy • Light Energy. • Nuclear Energy
What is Mechanical Energy? • Mechanical energy is the motion of objects. • An example is the energy you use to pick up a book.
What is Sound Energy? • Sound energy is the vibration of particles in a solid, liquid, or gas. • Sound can not travel through empty space.
What is Electromagnetic Energy? • Electromagnetic energyis transmitted through space in the form of electromagnetic waves. • Electromagnetic energy is a combination of electrical and magnetic forces. • Visible light is a form of electromagnetic energy, as well as x-rays and microwaves. • The Sun releases large amounts of electromagnetic energy, some of which is absorbed by Earth.
What is Electrical Energy? • Electrical energy comes from the charges in atoms of matter. • Electrical energy is the force of opposite charges (“+” and “-”) attracting. • Lightning, static, and current are forms of electrical energy.
What is Magnetic Energy? • Magnetic energy comes from the organization of atoms in a material. • Magnetic energy is the force of opposite poles (north and south) attracting.
What is Nuclear Energy? Nuclear energy is the energy holding an atom together.
What is Chemical Energy? • Chemical energy is energy that is stored in the chemical composition of matter. • An example is the energy used by cells in your body comes from the chemical energy in the food you eat.
What is Thermal Energy? • Thermal energy, is the energy from the movement of molecules.
Thermal Energy – “Heat” • Heat is the transfer of thermal energy between objects. • Heat always flows from the warmer objects to the cooler objects. • Temperature is the measure of how fast the molecules of a substance are moving. The faster the molecules move, the higher the temperature.
Conservation of Energy • Energy can not be created nor destroyed. • Energy can be transferred from one form to another.
Energy Transfers • One form of energy can turn into another form. • An example is when a ball is thrown (mechanical energy) against a wall, some of this energy is converted into sound and heat so the ball does not bounce back as far. • Most energy that is “wasted” in a transfer is converted to heat energy.
Energy Transfers: Remote Car • Batteries (chemical to electrical) • Electrical (electrical to electrical) • Lights flash (electrical to light) • Motor turns (electrical to mechanical) • Motor makes noise (mechanical to sound) • Motor gets warm (mechanical to heat) • Wheels turn (mechanical to mechanical) • Friction on floor (mechanical to heat and sound)
Energy Transfers • Wind - up mouse • Jack - in - the - box