Ch.9, Sec.1 – What Is Energy?

1. Energy and Work: Working Together • energy: the capacity to do work Ch.9, Sec.1 – What Is Energy? • work is done when a force causes an object to move in the direction of the force • when one object does work on another, energy is transferred from the 1st object to the 2nd • therefore, work is a transfer of energy! • energy is expressed in units of Joules (J) - all matter has atoms; therefore, all matter has energy!!!!!

2. Ch.9, Sec.1 – What Is Energy? • Kinetic Energy • kinetic energy: the energy of motion • all moving objects have kinetic energy & this energy can be used to do work • kinetic energy can be found using the following formula: KE = mv² 2 - m stands for mass in kilograms, v stands for the objects speed (the more speed & mass of an object means greater kinetic energy) • speed has a greater effect on kinetic energy than mass (faster cars cause greater crashes)

3. Ch.9, Sec.1 – What Is Energy? • Potential Energy • potential energy: the energy that an object has because of the position, shape, or condition of the object • any object elevated from the ground has gravitational potential energy (the more weight & height means greater GPE) - gravitational potential energy can be found using the following formula: GPE = weight x height • GPE is expressed using Newton-meters • height of GPE is a measure of how far an object has to fall

4. Ch.9, Sec.1 – What Is Energy? • Mechanical Energy • mechanical energy: the total energy of motion and position of an object (can be all potential, all kinetic, or some of each) • mechanical energy can be found using the following formula: ME = PE + KE • mechanical energy remains the same unless it transfers some of its energy to another object • even if mechanical energy stays the same, potential or kinetic energy can increase or decrease

5. Ch.9, Sec.1 – What Is Energy? • Other Forms of Energy • thermal energy: all of the kinetic energy due to random motion of the particles that make up an object • there’s more kinetic energy in gases than solids because of the molecular movement

6. Ch.9, Sec.1 – What Is Energy? • chemical energy: the energy of a compound that changes as its atoms are rearranged - chemical energy is a form of potential energy because it depends on the position & arrangement of the atoms in the compound

7. Ch.9, Sec.1 – What Is Energy? • electrical energy: the energy of moving electrons - changing positions of magnets at power plants provides electrical energy (potential energy too)

8. Ch.9, Sec.1 – What Is Energy? • sound energy: the energy caused by an object’s vibrations (potential energy turned into kinetic energy) • light energy: energy produced by the vibrations of electrically charged particles • light energy can travel through a vacuum! (an area with little or no atoms, like deep space)

9. Ch.9, Sec.1 – What Is Energy? • nuclear energy: the energy that comes from changes in the nucleus of an atom • energy can be from fusion where atoms can join together to create electrical energy (Sun) - energy can be from fission where atoms can be split apart in the nucleus to create a lot of potential energy (uranium in the atomic bombs)