Energy and Its Forms

Work

Work is a transfer of energy.

Key Words

-Chemical Energy -Elastic Potential Energy -Electrical Energy -Electromagnetic Energy -Energy -Gravitational Potential Energy -Kinetic Energy -Mechanical Energy -Nuclear Energy -Potential Energy -Thermal Energy

Chemical Energy

Campers toast marshmallows over a campfire. The source of energy for the fire is the energy stored in wood. When the wood is burned, energy is released and heats the marshmallows as well as the area around the campfire. The energy stored in wood is chemical energy. Chemical energy is the energy stored in chemical bonds. When bonds are broken, the released energy can do work. All chemical compounds, including fuels such as coal and gasoline, store energy. For example, cars can use the chemical energy stored in gasoline to move about. The gasoline is burned in the car's engine and some of its chemical energy is converted into mechanical energy to move the car.

Potential Energy

Potential energy is energy that is stored as a result of position or shape.

Gravitational Potential Energy

Potential energy that depends upon an object's height is called gravitational potential energy. This type of potential energy increases when an object is raised to a higher level. An object's gravitational potential energy depends on its mass, its height, and the acceleration due to gravity. The gravitational potential energy an object gains is equal to its weight (mg) multiplied by its height (h). To calculate gravitational potential energy in joules, the mass of the object is expressed in kilograms and the height of the object is expressed in meters. The acceleration due to gravity, g, has a value in SI units of 9.8 m/s^2 on Earth. Note that height is measured from the ground or floor or some other reference level. Potential energy (PE)=mgh

Objectives

-Describe the realtionship between work and energy -Relate kinetic energy to mass and speed and calculate these quantities -Analyze how potential energy is related to an object's position and give example of gravitational and elastic potential energy -Solve equations that relate an object's gravitational potential energy to its mass and height -Give example of the major forms of energy and explain how each is produced

Thermal Energy

Almost all of the matter around you contains atoms. These particles are always in random motion and thus have kinetic energy. The total potential and kinetic energy related to the motion of all the microscopic particles in an object make up its thermal energy. When an object's atoms move faster, its thermal energy increases and the object becomes warmer.

Electrical Energy

Electrical energy is the energy associated with electric charges. Electric charges can exert forces that do work. Batteries, which convert chemical enery to electrical energy, are used to operate portable CD players, flashlights, and calculators. Electrical energy also occurs in nature. The powerful bolts of lightning are produced by electrical energy.

Energy

Energy is the ability to do work. Energy is transferred by a force moving an object through a distance.

Mechanical Energy

The energy associated with the motion and position of everyday objects is mechanical energy. Don't be confused by the name, however. Mechanical energy is not limited to machines. Mechanical energy is the sum of an object's potential energy and kinetic energy. Speeding trains, bouncing balls, and sprinting athletes all hae mechanical energy. Mechanical energy does not include thermal energy, chemical energy, or other forms of energy associated with the motion or the arrangement of atoms or molecules. Most of these other forms of energy do involve kinetic or potential energy, but no an atomic scale. However, the mechanical energy of a speeding train and a spinting athele comes from the chemical of the train's fuel and the sprinter's body cells.

Kinetic Energy

The energy of motion is called kinetic energy. The kinetic energy of any moving object depends upon its mass and speed. To calculate the kinetic energy of an object in joules, multiply 1/2 by the object's mass (m) in kilograms and the square of its speed (v) in meters per second. Kinetic energy (KE)=1/2mv^2

Forms of Energy

The major forms of energy are mechanical energy, thermal energy, chemical energy, electrical energy, electromagnetic energy, and nuclear energy. Each of these forms of energy can be converted into other forms of energy.

Nuclear Energy

The nucleus of an atom is held together by strong and weak nuclear forces, which can store an enormous amount of potential energy. The energy stored in atomic nuclei is known as nuclear energy. A nuclear power plant uses nuclear fission reactions to generate electricity. Nuclear fission is a process that releases energy by splitting nuclei apart. A second type of nuclear reaction, nuclear fusion, releases energy when less massive nuclei combine to form a more massive nucleus. The heat and light of the sun are produced by the fusion of hydrogen nuclei into helium nuclei.

Elastic Potential Energy

The potential energy of an object that is stretched or compressed is known as elastic potential energy. Something is said to be elastic if it springs back to its original shape after it is stretched or compressed.

Electromagnetic Energy

The sun radiates electromagnetic energy into space and is the source, either directly or indirectly, of most of the world's energy supplies. Electromagnetic energy is a form of energy that travels through space in the form of waves. Visible light and X-rays are examples of electromagnetic energy. Because electromagnetic waves can travel long distance through air and space, they are often used for communication.