Transcript Ch. 13
Ch. 13 Energy What is Energy • Energy- The ability to do work or cause change. • Think of work as transferred energy. • Think of power as the rate at which energy is transferred or the amount of energy transferred in a unit of time. • Power= energy transferred/ time Question • What is power in terms of energy? Two basic kinds of energy • Kinetic and potential • Kinetic energy is the energy of an object due to its motion. (moving) • Depends on the mass And velocity. - KE increases if mass and velocity increases. Calculating KE • KE= ½ X mass X velocity squared. • The velocity of an object will have a greater effect on its kinetic energy. • Ex. Doubling the mass will double the KE, Doubling the velocity will quadruple its KE. - We measure energy in Joules (J). Question • Which has a greater effect on an objects kinetic energy? Mass or velocity Potential Energy • Stored energy that results from the position or shape of an object. • PE related to an objects height is gravitational Potential Energy. • GPE is equal to the work done to lift it. • GPE = weight X height • The more an object weighs or the greater the height, the greater the GPE. Question • A skier weighs 500 newtons. If the ski jump is 40 meters high, what is the GPE. • If the next skier weighed 600 newtons, would they have a greater GPE? Elastic potential energy • This happens when an object gains PE by stretching or compressing it. Ex. • An archer pulls back the arrow on a bow. The bow now has PE. • when the string is released it sends the arrow flying. Section 2, Forms of Energy • • • • • • Mechanical energy Thermal energy Electrical energy Chemical energy Nuclear energy Electromagnetic energy Mechanical Energy • Energy associated with position and motion of an object. • Ex. Quarterback throwing a football. • The QB transfers ME to the football. • Combination of its own PE and KE. • Ex. A thrown football’s ME is a combination of its position above the ground and its motion. • ME= Potential Energy = Kinetic Energy Question • What two forms of energy combine to make ME? Thermal Energy • The total PE and KE of particles in an object. • If the particles in the object are moving fast the object will be hot. (lava) • If the particles in the object are moving slow then the object will be cold. (ice cream) Question • What happens to the particles in a scoop of ice cream as it melts? • What happens to the lava as it moves away from the volcanoe? Electrical Energy • Energy of electric charges. • Ex. Shock from a door knob, lighting, runs through power lines, etc. • Can be KE or PE. Chemical Energy • Is PE stored in the chemical bonds that hold chemical compounds together. • It is found in almost everything. • When bonds in chemical compounds break, new chemical compounds may form. Nuclear Energy • • • • Stored in the nucleus of an atom. Released during a nuclear reaction. Nuclear Fission- occurs when a nucleus splits. Ex. Nuclear power plants use fission reactions to produce electricity. • Nuclear Fusion- occurs when nuclei of atoms fuse, or join together. • Ex. This occurs in the sun, releasing tremendous amounts of energy. Electromagnetic Energy • Energy that travels in waves. • Ex. Sunlight, X-rays • Have some electrical properties and magnetic properties.