Chapter 15 Page

Chapter 15 Section 1 Pg

Energy and Work Work- done when a force moves an object through a distance, a transfer of energy – Measured in joules (J) Energy- the ability to do work – It is known by the changes it causes – Examples are sound and motion – Measured in joules (J) 1 joule = 1 newton-meter When work is done on an object, energy is transferred to that object

Kinetic Energy Kinetic Energy- the energy of motion – Comes from the Greek work kinetos, meaning “moving” – The kinetic energy of any moving object depends upon its mass and speed.

Math Practice Page 448

Potential Energy Potential Energy- energy that is stored as a result of position or shape – Stored energy gets converted into kinetic energy – You can store energy just by picking up a book and holding it. Let go, and that stored energy will turn into the kinetic energy of motion

Gravitational Potential Energy Gravitational Potential Energy- potential energy that depends upon an object’s height – The PE increases when an object is raised to a higher level – Depends on an object’s mass, height, and acceleration due to gravity (9.8 m/s 2 )

Elastic Potential Energy Elastic Potential Energy- PE of an object that is stretched or compressed – Said to be elastic if it springs back to its original shape after it is stretched or compressed – Can also be stored in objects that are compressed, such as springs – Broken rubber band: it’s elastic PE is converted into kinetic energy

Forms of Energy All energy can be considered to be kinetic energy, potential energy, or the energy in fields such as those produced by electromagnetic waves – Ex: fireworks, nuclear energy, lightning bolts, etc. The major forms of energy are mechanical energy, thermal energy, chemical energy, electrical energy, electromagnetic energy, and nuclear energy

Mechanical Energy Mechanical Energy- the energy associated with the motion and position of everyday objects – Not limited to machines – The sum of an object’s potential energy and kinetic energy Mechanical Energy = KE + PE – Ex: speeding trains, bouncing balls, sprinting athletes Does NOT include thermal, chemical or other energy associated with the motion or arrangement of atoms or molecules

Thermal Energy Thermal Energy- the total potential and kinetic energy of all the microscopic particles in an object When an object’s atoms move faster, its thermal energy increases and the object becomes warmer

Chemical Energy Chemical Energy- the energy stored in chemical bonds – When bonds are broken, the released energy can do work – Example: wood burning, when gasoline is burned

Electrical Energy Electrical Energy- the energy associated with electric charges – Electric charges can exert forces that do work – Example: batteries

Electromagnetic Energy Electromagnetic Energy- a form of energy that travels through space in the form of waves – Radiated by the sun – Examples: visible light, X-rays

Nuclear Energy Nuclear Energy- the energy stored in atomic nuclei – Examples: nuclear fission (is a process that releases energy by splitting nuclei apart) and nuclear fusion (releases energy when less massive nuclei combine to form a more massive nucleus)

Chapter 15 Section 2 Page

Energy Conversion Energy can be converted from one form to another, known as energy conversion Examples: – Wind-up toys: store elastic PE in spring, when released the PE is converted to KE and the toy moves – Light bulbs: convert electrical energy to thermal and electromagnetic energy – See more on page 454 of book

Conservation of Energy The law of conservation of energy states that energy cannot be created or destroyed – Energy can be converted from one form to another – In a closed system, the amount of energy present at the beginning of a process is the same as the amount of energy at the end – See example on page 455

Energy Conversions Gravitational potential energy of an object is converted to the kinetic energy of motion as the object falls Conversions between KE and PE can happen in both directions

Energy Conversion in Pendulums Rope swing is an example of a pendulum. – Pendulum consists of a weight swinging back and forth from a rope or string – KE and PE undergo constant conversion as a pendulum swings. – At HIGHEST point in swing, pendulum is momentarily motionless: the weight at the end has zero KE and maximum PE – As is swings downward, PE is converted to KE – At the bottom of the swing, the pendulum has maximum KE and zero PE

Energy Conversion in the Pole Vault Pole-vaulter’s KE is partially converted into elastic PE as the pole bends. It springs back into shape, propelling the pole-vaulter upward – As he soars KE decreases while he gains gravitational PE – At the highest point, gravitational PE begins to convert back to KE

Energy Conversion Calculations Conservation of Mechanical Energy – When friction is small enough to be ignored Math Practice pg. 458

Energy and Mass Einstein ( ) – Developed theory of relativity E = mc 2 (Energy = mass X c-the speed of light squared) Einstein’s equation, E =mc 2 says that energy and mass are equivalent and can be converted into each other – In other words: energy is released as matter is destroyed, and matter can be created from energy

Energy and Mass In nuclear fission and fusion reactions, large amounts of energy are released by the destruction of very small amounts of matter. The law of conservation of energy has been modified to say that mass and energy together are always conserved

Chapter 15 Section 3 Page

Nonrenewable Energy Resources Nonrenewable energy resources- exist in limited quantities, once used, cannot be replaced except over the course of millions of years Examples: oil, natural gas, coal, and uranium Fossil fuels: oil, natural gas, and coal – Creates pollution Many of these resources are being used faster than they can be replaced

Nonrenewable Energy Resources

Renewable Energy Resources Renewable energy resources- resources that can be replaced in a relatively short period of time – Most originate directly/indirectly from the sun – Example: hydroelectric, solar, geothermal, wind, biomass – Challenge is to find efficient ways to make these energy resources inexpensive and convenient

Renewable Energy Resources

Hydroelectric Energy Hydroelectric energy- energy obtained from flowing water As water flows downhill, its gravitational PE is converted into KE which can be used to turn turbines that are connected to electric generators Many hydroelectric power plants rely on dams – Cause a few environmental problems (fish spawning)

Hydroelectric Energy

Solar Energy Solar energy- sunlight that is converted into usable energy – nonpolluting

Geothermal Energy Geothermal energy- thermal energy beneath Earth’s surface Steam is used to drive electric generators Nonpolluting Not widely available

Other Renewable Resources Biomass energy- the chemical energy stored in living things – Can be converted directly into thermal energy (ex: wood burning) Hydrogen fuel cell- generates electricity by reacting hydrogen with oxygen – End product is water, nonpolluting

Renewable vs. Nonrenewable

Conserving Energy Resources Energy resources can be conserved by reducing energy needs and by increasing the efficiency of energy use Energy conservation- finding ways to use less energy or to use energy more efficiently – Turn of lights when not in use – Energy efficient products (appliances, cars, light bulbs)