Astronomy 100 Tuesday, Thursday 2:30 - 3:45 pm Tom Burbine [email protected] www.xanga.com/astronomy100Help DeskThe purpose of testsThe TestZodiacSlide 6Now there are 13 constellations in the zodiacSlide 8Slide 9Long Term ChangesSince most people did not seem enjoy the test?Another Homework Assignment (Due Thursday March 3rd)Homework assignments due next Tuesday2nd HW assignment due next Tuesday (Feb. 22)MatterEnergySlide 173 basic categories of energyKinetic energyPRS question #1AnswerThermal energyTemperature scalesIn ScienceSlide 25Gravitational Potential EnergyConverting Mass to EnergyE = mc2Who came up with it?Slide 30PRS question #2Slide 32Mass-EnergySlide 34AtomsSlide 36Slide 37ElementsChargeSlide 40DefinitionsFirst nuclear weaponsAtoms make up moleculesSlide 44Questions?Astronomy 100Tuesday, Thursday 2:30 - 3:45 pmTom [email protected]/astronomy100Help Desk•There is an Astronomy Help Desk in HAS 205. It will be open from Monday through Thursday from 7-9 pm.The purpose of tests•So you study the material•So you learn the material better•Test how well you know the material•Decide your gradeThe Test•The average was 71.5% (28.6 out of 40)•Grades ranged 12 to 39Zodiac•The zodiac is an imaginary belt in the heavens extending approximately 8 degrees on either side of the Sun's apparent path (the ecliptic), that includes the apparent paths of the Moon and the planets Mercury, Venus, Mars, Jupiter, Saturn, Uranus, and Neptune.Now there are 13 constellations in the zodiac•Why?•Originally the zodiac was divided into 12 equally spaced “signs”•However, some constellations are big, some are small•When the astronomers redid the boundaries, a 13th constellation was added to the zodiacLong Term ChangesSince most people did not seem enjoy the test?Another Homework Assignment(Due Thursday March 3rd)•Make up a test question•Multiple Choice•A-E possible answers•1 point for handing it in•1 point for me using it on testHomework assignments due next Tuesday•Two due next Tuesday (Feb. 22)•One is from this sheet that I am handing out•Two calculations•Worth 1 HW point2nd HW assignment due next Tuesday (Feb. 22)•I want you to pick an element•Write its symbol•Is it a solid, metal, or gas?•Atomic Number•Atomic Mass•Its isotopes•What this element is used for?•http://www.webelements.com/•Worth 1 HW pointMatter•Matter is materialEnergy•Energy is what makes matter move•In English Units, we use calories to measure energy•In science (and in this class), we will use joules to measure energy3 basic categories of energy•Kinetic energy – energy of motion•Potential energy – energy being stored for possible conversion into kinetic energy•Radiative energy – energy carried by lightKinetic energy•Kinetic energy = ½ mv2•m is mass in kg•v is velocity in meters/s•A joule has units of kg-m2/s2PRS question #1•How much energy does a 2 kg rock have if it is thrown at 20 m/s?•Kinetic energy = ½ mv2•A) 200 J•B) 400 J•C) 40 J•D) 800 JAnswer•KE = ½ * 2 * (20) *(20) = 400 joulesThermal energy•Temperature – average kinetic energy of particles•Higher temperature – more kinetic energy, particles moving faster•For examples, air molecules around you are moving at ~500 m/sTemperature scales•In America, we use Fahrenheit•Water freezes at 32 degrees F•Water boils at 212 degrees F•Everywhere else, they use Celsius•Water freezes at 0 degrees C•Water boils at 100 degrees CIn Science•Temperature is measured in Kelvin•Zero Kelvin is absolute zero – nothing moves•Add 273.15 to the Kelvin temperature to get the Celsius temperature•273.15 Kelvin = 0 degrees CelsiusGravitational Potential Energy•Gravitational Potential Energy released as an object falls depends on its mass, the strength of gravity, and the distance it falls•For example, your gravitational potential energy increases as you go farther up in the air•This is because you hit the ground at a faster speed if you jump from a higher distanceConverting Mass to Energy•What is the most famous formula in the world?E = mc2•m is mass in kilograms•c is speed of light in meters/s•So E is in joules•very small amounts of mass may be converted into a very large amount of energy andWho came up with it?PRS question #2•How much energy can be produced if you can convert 10 kg of material in energy?•E = mc2•A) 3.0 x 108 J•B) 3.0 x 1016 J•C) 9.0 x 1017 J•D) 9.0 x 1010 JAnswer•E = 10 kg * (3 x 108 m/s) * (3 x 108 m/s)•E = 10* (9 x 1016) J•E = 90 x 1016 J•E = 9.0 x 1017 JMass-Energy•So Mass is a form of potential energy•Where is one place where you see mass converted into energy?Atoms•Atoms are made up of 3 types of particles•Protons – positive charge (+1)•Electrons – negative charge (-1) •Neutrons – neutral charge (no charge)•Protons and Neutrons are found in the nucleusElements•Different elements have different numbers of protons•The properties of an atom are a function of the electrical charge of its nucleusCharge•If an atom has the same number of electrons and protons, it has a neutral charge•More electrons than protons, negatively charged•More protons than electrons, positive charged•Neutrons have neutral charge so don’t affect the charge of an atomDefinitions•Atomic Number – Number of protons•Atomic Mass – Number of protons and neutrons•U235 – atomic mass 92- atomic number•Isotopes – Same number of protons but different numbers of neutronsFirst nuclear weapons•Worked by nuclear fission•Use Uranium-235•If a free neutron runs into a U-235 nucleus, the nucleus will absorb the neutron without hesitation, become unstable and split immediately•The energy released by a single fission is due to the fact that the fission products and the neutrons, together, weigh less than the original U-235 atomAtoms make up molecules•H2O•CO2•CH4•Atoms made up with 2 or more different atoms are called