Energy: Forms and Changes
The Energy Story
Nature of Energy Energy is all around you! l You can hear energy as sound. l You can see energy as light. l And you can feel it as wind.
Nature of Energy You use energy when you: l hit a softball. l lift your book bag. l compress a spring.
Nature of Energy Living organisms need energy for growth and movement.
Nature of Energy Energy is involved when: l a bird flies. l a bomb explodes. l rain falls from the sky. l electricity flows in a wire.
Nature of Energy What is energy that it can be involved in so many different activities? l Energy can be defined as the ability to do work. l If an object or organism does work (exerts a force over a distance to move an object) the object or organism uses energy.
Nature of Energy Because of the direct connection between energy and work, energy is measured in the same unit as work: joules (J). In addition to using energy to do work, objects gain energy because work is being done on them.
Forms of Energy Thermal energy Mechanical energy Chemical energy Electromagnetic energy Nuclear energy Sound energy Light energy
What is Thermal Energy? Thermal energy is the energy created by moving particles inside a substance. More movement of particles = more thermal energy The transfer of thermal energy is known as heat Heat energy can be produced by friction. A hot object is one whose atoms and molecules are excited and show rapid movement. A cooler object's molecules and atoms will show less movement.
What is Mechanical Energy? Energy due to a object s motion (kinetic) or position (potential). The bowling ball has mechanical energy. When the ball strikes the pins, mechanical energy is transferred to the pins!
Mechanical Energy When work is done to an object, it acquires energy. The energy it acquires is known as mechanical energy.
Examples of Mechanical Energy
Mechanical Energy When you kick a football, you give mechanical energy to the football to make it move.
Mechanical Energy When you throw a balling ball, you give it energy. When that bowling ball hits the pins, some of the energy is transferred to the pins (transfer of momentum).
What types of energy are shown below? Mechanical and Thermal Energy (Don t forget friction)
What is Chemical Energy? Energy that is available for release from chemical reactions. The chemical bonds in a matchstick store energy that is transformed into thermal energy when the match is struck.
Chemical Energy Chemical Energy is required to bond atoms together. And when bonds are broken, energy is released.
Chemical Energy Fuel and food are forms of stored chemical energy.
Examples of Chemical Energy
What is Electromagnetic Energy? Electromagnetic energy is a term used to describe all the different kinds of energies released into space by stars such as the Sun They include: Radio Waves TV waves Radar waves Heat (infrared radiation) Light Ultraviolet Light (This is what causes Sunburns) X-rays (Just like the kind you get at the doctor's office) Short waves Microwaves (like in a microwave oven) Gamma Rays
Electromagnetic Energy Power lines carry electromagnetic energy into your home in the form of electricity.
Electromagnetic Energy Light is a form of electromagnetic energy. Each color of light (Roy G Bv) represents a different amount of electromagnetic energy. Electromagnetic Energy is also carried by X-rays, radio waves, and laser light.
What is Electrical Energy? Energy caused by the movement of electrons Easily transported through power lines and converted into other forms of energy
Nuclear Energy The nucleus of an atom is the source of nuclear energy.
Nuclear Energy When the nucleus splits (fission), nuclear energy is released in the form of heat energy and light energy. Nuclear energy is also released when nuclei collide at high speeds and join (fuse).
Nuclear Energy The sun s energy is produced from a nuclear fusion reaction in which hydrogen nuclei fuse to form helium nuclei.
Nuclear Energy Nuclear energy is the most concentrated form of energy.
What type of energy is shown below? Chemical Energy
What types of energy are shown below? Electrical, Mechanical and Electromagnetic Energy
What type of energy is shown below? Chemical Energy (yummy)
What type of energy is shown below? Thermal Energy
Energy Conversion Energy can be changed from one form to another. Changes in the form of energy are called energy conversions.
Energy conversions All forms of energy can be converted into other forms. l The sun s energy through solar cells can be converted directly into electricity. l Green plants convert the sun s energy (electromagnetic) into starches and sugars (chemical energy).
Other energy conversions l In an electric motor, electromagnetic energy is converted to mechanical energy. l In a battery, chemical energy is converted into electromagnetic energy. l The mechanical energy of a waterfall is converted to electrical energy in a generator.
Energy Conversions In an automobile engine, fuel is burned to convert chemical energy into heat energy. The heat energy is then changed into mechanical energy.
Chemical à Heat à Mechanical
States of Energy The most common energy conversion is the conversion between potential and kinetic energy. All forms of energy can be in either of two states: l Potential l Kinetic
States of Energy: Kinetic and Potential Energy Kinetic Energy is the energy of motion. Potential Energy is stored energy.
Kinetic Energy The energy of motion is called kinetic energy. The faster an object moves, the more kinetic energy it has. The greater the mass of a moving object, the more kinetic energy it has. Kinetic energy depends on both mass and velocity.
Kinetic Energy The amount of the energy an object possesses due to its motion *Kinetic energy = 1/2 mv 2 mass, m (kg) velocity, v (m/s) *Note v 2 means that the amount of kinetic energy increases VERY rapidly with increasing speed
Potential Energy Potential Energy is stored energy. l Stored chemically in fuel, the nucleus of atom, and in foods. l Or stored because of the work done on it: Stretching a rubber band. Winding a watch. Pulling back on a bow s arrow. Lifting a brick high in the air. Roller coaster at the top of the hill
Gravitational Potential Energy Potential energy that is dependent on height is called gravitational potential energy.
Gravitational Potential Energy A waterfall, a suspension bridge, and a falling snowflake all have gravitational potential energy.
Potential Energy Gravitational Potential energy (GPE) is the energy an object (mass) possesses because of its position relative to the ground (9.8 m/s 2 ) mass Gravitational Potential Energy = mgh h m=mass g=rate of acceleration due to gravity (9.8 m/s 2 h=height
Potential Energy Energy that is stored due to being stretched or compressed is called elastic potential energy.
Gravitational Potential Energy If you stand on a 3-meter diving board, you have 3 times the G.P.E, than you had on a 1-meter diving board.
Energy is Conserved Conservation of Energy is different from Energy Conservation. Energy Conservation means using energy wisely Conservation of Energy means energy is neither created nor destroyed. The TOTAL amount of energy in the Universe is constant, stays the same!! Don t we create energy at a power plant? Oh that this were true no, we simply transform energy at our power plants Doesn t the sun create energy? Nope it exchanges mass for energy
Kinetic-Potential Energy Conversion Roller coasters work because of the energy that is built into the system. cars are pulled mechanically up the tallest hill, giving them a great deal of potential energy. the conversion between potential and kinetic energy powers the cars throughout the entire ride.
Kinetic vs. Potential Energy At the point of maximum potential energy, the car has minimum kinetic energy.
Energy Transformations Most mechanical processes involve conversions between KE, PE, and work l A car rolling down a hill into a valley PE at the top of the hill is converted into KE as the car rolls down the hill KE is converted to PE as the car rolls up the other side BUT, the TOTAL amount of energy remains the same! IT S THE LAW! Law of Conservation of Energy!
A Total PE=10 J D B E C A B C All potential energy P.E. = 10 J K.E. = 0 J D Potential energy & Kinetic energy P.E. = 5 J; K.E. = 5 J All kinetic energy (greatest speed) K.E. = 10 J P.E. = 0 J All potential energy (stops for an instant) P.E. = 10 J K.E. = 0 J E Potential energy & Kinetic energy P.E. = 4 J; K.E. = 6 J
The Transformation of Energy Energy is conserved. Conservation of energy means it can change forms between kinetic and potential, but it never disappears. The total amount of energy is always the same. IT S THE LAW! Law of Conservation of Energy!
No Energy for Free No matter what, you can t create energy out of nothing: it has to come from somewhere. We can transform energy from one form to another; we can store energy, we can use energy from natural sources. The net energy of the entire Universe is constant. The best we can do is scrape up some useful crumbs.
Kinetic-Potential Energy Conversions As a basketball player throws the ball into the air, various energy conversions take place.
Ball slows down Ball speeds up
The Law of Conservation of Energy Energy can be neither created nor destroyed by ordinary means. l It can only be converted from one form to another. l If energy seems to disappear, then scientists look for it leading to many important discoveries.
Law of Conservation of Energy In 1905, Albert Einstein said that mass and energy can be converted into each other. He showed that if matter is destroyed, energy is created, and if energy is destroyed mass is created. 2 E = MC