Energy: Forms and Changes Chapter 16
Energy: is the ability to do work is measured in joules (J)
Objects can gain energy when work is done on them
There are five different forms of energy Mechanical Heat Chemical Electromagnetic Nuclear
Mechanical Energy of motion
Heat Internal motion of atoms The greater the motion, the more heat the object contains
Heat Energy
Chemical Energy found in the bonds of atoms Released when those bonds are broken
Chemical Energy
Moving electrical charge Electromagnetic Moving electrical charge
Electromagnetic Energy
Nucleus in atom break apart (fission) Nuclear or nuclei join (fusion)
Nuclear Energy
Energy can be classified as either kinetic or potential kinetic is the energy of movement potential is the energy of position or shape
Energy of position or shape Energy is stored for later use
If potential energy depends upon height (gravity), then formula is: GPE = weight X height (weight = mass X gravity constant) If a 10 N rock is sitting on a wall 10 meters high, what is its potential energy?
Kinetic Energy (KE) = mass X velocity2 Which affects KE the most – mass or velocity?
Kinetic or Potential Energy
Energy Conversions Like matter, energy is neither created nor destroyed by ordinary means; however, it can be changed from one form to another. All forms of energy can be converted to other forms.
Potential to Kinetic Conversions
At this position, is there kinetic and/or potential energy?
How many different ways can the sun’s energy be converted? How many different conversions of energy occur when one uses a hairdryer at home.
Energy Conversion
Part of Einstein’s theory of relativity deals with the concept that mass and energy are directly related. Einstein 1905
He stated that mass and energy can be converted into each other He stated that mass and energy can be converted into each other. If matter is destroyed, it becomes energy and energy can become mass. This is the theory of how the sun creates so much energy – some mass is destroyed causing much energy to be created.
E = mc2
How does energy relate to: speed? more energy, more speed momentum? energy is transferred force? energy needed to change motion power? rate of energy consumed work? energy is conserved (input vs output)