Transcript Energy
Energy Table of Contents What Is Energy? Book M – 5.1 Pg. 146-150 Forms of Energy Book M – 5.2 Pg. 151-155 Energy Transformations and Conservation Book M – 5.3 Pg. 158-163 Energy and Fossil Fuels Energy - What Is Energy? Energy, Work, and Power •The ability to do work or cause change is called energy. •When an object or living thing does work on another object, some of its energy is transferred to that object. •You can think of work then, as the transfer of energy. •Power is the rate at which energy is transferred, or the amount of energy transferred in a unit of time. Energy - What Is Energy? Power Practice Problem Find the power of a machine that transfers 450 J of energy in 9 seconds. Power = 450 Joules / 9 seconds Power = 50 J/s or watts Energy - What Is Energy? Energy • The two basic kinds of energy are kinetic energy and potential energy. • The energy an object has due to its motion is called kinetic energy. • Objects that are moving do work, and therefore have energy. • Stored energy that results from the position or shape of an object is called potential energy. • This energy has the “potential” to do work. Energy - What Is Energy? Kinetic Energy • Kinetic energy increases as mass and velocity increases. • Relationship between kinetic energy, mass, and velocity. Energy - What Is Energy? Exponents An exponent tells how many times a number is used as a factor. For example, 3 X 3 can be written as 32. You read this number as “three squared.” An exponent of 2 indicates that the number 3 is used as a factor two times. To find the value of a squared number, multiply the number by itself. 32 = 3 X 3 = 9 Practice Problem What is the value of the number 82? 64 Energy - What Is Energy? Kinetic Energy Practice Problem A 1,350 kg car travels at 12 m/s. What is its kinetic energy? Kinetic Energy = (1/2) x (1350 kg) x (12 m/s)² Kinetic Energy = 97,200 Joules Energy - What Is Energy? Gravitational Potential Energy • Potential Energy related to an object’s height is called gravitational potential energy. • Gravitational potential energy increases as weight and height increase. Energy - What Is Energy? Potential Energy Practice Problem A 380-N girl walks down a flight of stairs so that she is 2.5 m below her starting level. What is the change in the girl’s gravitational potential energy? GPE = (380 N) x (2.5 m) GPE = 950 J Her potential energy decreased by 950 Joules. Energy - What Is Energy? Elastic Potential Energy • The potential energy associated with objects that can be stretched or compressed is called elastic potential energy. Energy - What Is Energy? Links on Energy Click the SciLinks button for links on energy. Energy - Forms of Energy Mechanical Energy •The form of energy associated with the position and motion of an object is called mechanical energy. •You can find an object’s mechanical energy by adding the objects kinetic energy and potential energy. Energy - What Is Energy? Mechanical Energy Practice Problem If the kinetic energy of a falling apple is 5.2 J and its potential energy is 3.5 J, what is its mechanical energy? Mechanical Energy = Potential Energy + Kinetic Energy Mechanical Energy = 3.5 J + 5.2 J Mechanical Energy = 8.7 J Energy - Forms of Energy Calculating Mechanical Energy The kinetic energy of a 500-N diver during a dive from a 10-m platform was measured. These data are shown in the graph. Energy - Forms of Energy Calculating Mechanical Energy Reading Graphs: According to the graph, how much kinetic energy does the diver have at 8 m? About 1000 J Energy - Forms of Energy Calculating Mechanical Energy Calculating: Using the graph, find the kinetic energy of the diver at 6 m. Then calculate the diver’s potential energy at that point. Kinetic energy = about 2000 J; potential energy = about 3000 J Energy - Forms of Energy Calculating Mechanical Energy Inferring: The mechanical energy of the diver is the same at every height. What is the mechanical energy of the diver? About 5000 J Energy - Forms of Energy Other Forms of Energy •Most forms of energy, other than kinetic and potential, are associated with tiny particles that make up the objects. They include: • Thermal Energy – the total potential and kinetic energy of the particles in an object. • Electrical Energy – the energy of electric charges. • Chemical Energy – potential energy stored in the chemical bonds that hold the chemical compounds together. • Nuclear Energy – potential energy stored in the nucleus of an atom. • Electromagnetic Energy – the energy of light and other forms of radiation. Energy - Forms of Energy Links on Forms of Energy Click the SciLinks button for links on forms of energy. Energy - Energy Transformations and Conservation Energy Transformations • Most forms of energy can be transformed into other forms. • A change from one form of energy to another is called energy transformation. • There can be single or multiple transformations of energy. Energy - Energy Transformations and Conservation Transformations Between Potential and Kinetic Energy • One of the most common energy transformations is the transformation between potential energy and kinetic energy. • Examples: Waterfalls, Juggling, Pendulum, and Pole Vault Energy - Energy Transformations and Conservation Transformations Between Potential and Kinetic Energy A pendulum continuously transforms energy from kinetic to potential energy and back. Energy - Energy Transformations and Conservation Energy Transformations Activity Click the Active Art button to open a browser window and access Active Art about energy transformations. Energy - Energy Transformations and Conservation Conservation of Energy • The law of Conservation of Energy states when one form of energy is transformed to another, no energy is destroyed in the process. • Energy can not be created or destroyed. • Whenever a moving object experiences friction, some of its kinetic energy is transformed to thermal energy this shows that energy is not destroyed, just transformed. • Einstein discovered that matter can be transformed to energy. • Destroying a small amount of matter can release huge amounts of energy, so the law of conservation had to be adjusted to state that matter and energy together are always conserved. Energy Graphic Organizer Energy exists as Potential energy Kinetic energy measured in is the ability to do Joules Work can be Elastic Gravitational which at a given rate is Power