Chapter 4: ENERGY Section 1

The Nature of Energy

What is Energy? Energy is the ability to cause change. Every change that occurs requires energy.

Energy Has Different Forms Some forms of energy –Electrical –Chemical –Radiant –Thermal

Forms of Energy Some things can have more than one type of energy at a time. Energy can convert from one form to another. Energy can be stored in many ways.

Electrical Energy Electric circuit – electrical-circuit.htmlhttp:// electrical-circuit.html

Chemical Energy Chemical change animation – hemistry-i/physical-chemical- changes/physical-chemical-changes- animation.phphttp:// hemistry-i/physical-chemical- changes/physical-chemical-changes- animation.php –How MRE heaters work

Radiant Energy

More Radiant Energy Examples

Thermal Energy

Other Forms of Energy... There are also these types of energy: –Kinetic energy is the energy of a moving object. –Potential energy comes in 3 different forms: Gravitational potential is stored energy due to an object’s position. Elastic potential energy stored by something that can stretch, compress, or bend—like a rubber band, spring, or pole vault. Chemical potential energy is the energy stored in chemical bonds.

Kinetic Energy Kinetic energy is measured in joules Use the formula KE=1/2 mass x velocity 2 In other words: 1/2mv 2

Gravitational Potential Energy Watch out for falling rocks... and cows! m/content/physics/phys ics-i/work-energy- power/potential-energy- animation.php

Converting GPE to Kinetic Energy As an object falls, its potential energy is converted into kinetic (moving) energy. –As the object approaches the ground, it will have the greatest kinetic energy—and the least potential energy. The gravitation potential energy (GPE) can be calculated using this formula: –Mass (kg) x acceleration due to gravity (m/s 2 ) x height of object (m) –In other words: kg x m/s 2 x m = GPE or mgh = GPE

Elastic Potential Energy Watch this: And these: M M

Chemical Potential Energy Watch this: R0087w And this: uFbV0&feature=list_related&playnext=1&li st=PLA46E338EFA196C4E uFbV0&feature=list_related&playnext=1&li st=PLA46E338EFA196C4E

Section 2: Conservation of Energy

Electrical Energy Transformed into –Thermal energy –Radiant energy –Mechanical energy –Sound Energy

Chemical Energy Transformed into –Radiant energy –Heat –Kinetic/mechanical energy –Thermal energy –Car Engine Animation

Kinetic to Potential Energy Pendulum swinging is a good example.

More Potential to Kinetic Falling Objects

Projectile Motion Conversion from kinetic to potential to kinetic are taking place.

Energy Transformations in a Swing Another good example of kinetic to potential energy transformations. pyC9aIhttp:// pyC9aI

Law of Conservation of Energy Energy cannot be created or destroyed, it simply changes form. Matter can be converted into energy through –Fusion—atomic nuclei fusing together on.htmlhttp://library.thinkquest.org/17940/texts/fission/fissi on.html –Fission—atomic nuclei being broken apart htmlhttp:// html

More on the LAW of Conservation of Energy It may seem as though energy is being lost, as with the pendulum example, but some energy is generally lost to FRICTION. –Friction creates thermal energy. –Air resistance (another type of friction) slows things down. GRAVITY is also a factor in stopping motion.

Conserving energy is not the same as “Conservation of Energy” To conserve energy means to not waste energy resources. On the other hand, the law of conservation of energy is a universal principal that describes what happens to energy as it is transferred from one object to another or one form to another.

Your Body’s Use of Energy Your body stores energy from the foods you eat in the form of fat and other chemicals. When your body needs that energy, it will “burn” the fat. In other words, the chemical energy from fat will convert into thermal and mechanical (kinetic) energy.

How Do We Measure Energy in Food? The label used for a unit of food energy is the Calorie (note it is capitalized). 1 C is equal to about 4,184 Joules. A gram of fat consumed contains about 9 C. A gram of carbohydrates or proteins contain about 4 C of energy. –Carbs include sugars, starches, and fiber Fat contains the most energy of all foods.