Forces and Energy We have studied FORCES and Newton’s laws. Forces can be classified into 4 groups There are 4 Universal Forces Electricity Magnetism Strong Nuclear Force Weak Nuclear Force Chemical changes involve electro – magnetic forces b/c they rely on electric charges of atoms and their parts. Strong nuclear force holds protons and neutron together in nucleus. Stronger than repulsive forces of protons for each other. Weak = short range attraction of subatomic particles for each other.

Energy is the ability to do work Energy is transferred when a force moves and object through a distance “Work is the transfer of energy” Both can be measured in joules (Newton-meter) NOTE: Work is the force on an object over a distance

We are going to turn now to a study of energy … We are going to turn now to a study of energy ….how those forces can be put to work.

Energy - the ability to do work. 15.1 Kinetic Energy – energy of motion Kinetic Energy = ½ mv2 Potential Energy – stored energy Potential energy = mgh Gravitational Potential Energy Elastic Potential Energy Energy is transferred by a force moving an object through a distance. Work is the transfer of energy. Joules = 1 newton-meter Joules (J) The work done by a force of one Newton traveling through a distance of one meter Elastic PE – can be compressed or stretched and return to original shape.

Forms of Energy Mechanical Energy – sum of potential and kinetic energy (ex. Speeding train) Thermal Energy – sum of PE and KE of all the particles in an object. Faster motion - >Thermal E Chemical Energy – chemical bonds that hold together chemical compounds. Electrical Energy – transfer of electrons (Batteries) Electromagnetic Energy – energy that travels through space as waves (ex. Sun light or x-rays) Nuclear Energy – energy that holds the nucleus together. Released in nuclear fission.

Forms of Energy Mechanical Energy – sum of potential and kinetic energy (ex. Speeding train)

Forms of Energy Thermal Energy – sum of PE and KE of all the particles in an object.

Types of Energy Chemical Energy – chemical bonds that hold together chemical compounds.

Types of Energy Electrical Energy – transfer of electrons

Forms of Energy Electromagnetic Energy – energy that travels through space as waves

Electromagnetic Waves http://www.astronomynotes.com/light/emanim.gif

Forms of Energy Nuclear Energy – energy that holds the nucleus together. Released in nuclear fission.

Energy Conversion and Conservation 15.2 Law of Conservation of Energy – energy can not be created or destroyed (just change forms)

Energy Conversion and Conservation 15.2 Energy Conversion – from one form to another. Ex. Lighting a match chemical  thermal  chemical Ex. Hydroelectric power plant Gravitational Potential energy kinetic energy  electrical energy Conservation of Mechanical Energy (KE + PE) beginning = (KE + PE) end

What are energy conversions in picture of pole vaulter

Disc Streaming Physics of Fun Link to real player

Energy Conversion and Conservation 15.2 Einstein’s equation, E = mc2, says that Energy and Mass are equivalent and can be converted into each other.

Energy Resources 15.3 Nonrenewable Energy Resources Oil, natural gas, coal, and Uranium. Renewable Energy Resources Hydroelectric energy, solar, geothermal, biomass, hydrogen fuel cell Conserving Energy Resources

Integrated Science SOURCES OF ENERGY

Renewable vs. Non-Renewable Hydroelectric Solar Geo-Thermal Wind Hydrogen Ocean Thermal Energy Conversion Biomass Coal Petroleum Natural Gas Uranium

Non-Renewable Sources Are available in limited quantities Are not evenly distributed throughout the world Cannot be easily replaced (takes million of years)

Coal Large deposits in the USA Burns “dirty”, adding sulfur oxides and nitrogen oxides to the air as well as C02. Contributes to global warming, air pollution and acid rain

Petroleum We do not have enough to meet our needs in the USA, so must import from unfriendly nations Produces air pollution and contributes to global warming

Natural Gas Burns cleaner than other fossil fuels Still produces carbon dioxide and contributes to global warming Not always easy to get to in the ground

Offshore Natural Gas Rig

Uranium Open pit mines damage environment Leftover dust is radioactive waste Rare and only found in a few countries, such as Canada, Kazakhstan and Australia

RENEWABLE RESOURCES:

Hydroelectric Almost no pollution Lakes can be used for recreation Expensive to construct Limited sites People and wildlife displaced and ecosystems damaged

Solar No pollution except in manufacture and transportation of panels Quiet Can be used in remote locations High cost of panels and installation Only works when sunny

Geo-Thermal Mainly used to heat homes in USA Clean Some electricity needed to pump water through system Expensive to install Requires land so not good where population is dense

Wind Available world-wide Clean Noisy and some do not like view Only works when wind blows Energy must be transported to grid by wires

Biomass Made from plants or animals Can be a way to utilize waste Produces pollution and contributes to global warming Can be made with domestic resources