Transcript zodiac
Astronomy 100 Tuesday, Thursday 2:30 - 3:45 pm Tom Burbine [email protected] www.xanga.com/astronomy100 Help 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 grade The Test • The average was 71.5% (28.6 out of 40) • Grades ranged 12 to 39 Zodiac • 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 zodiac Long Term Changes Since 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 test Homework 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 point 2nd 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 point Matter • Matter is material Energy • 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 energy 3 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 light Kinetic energy • • • • Kinetic energy = ½ mv2 m is mass in kg v is velocity in meters/s A joule has units of kg-m2/s2 PRS 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 J Answer • KE = ½ * 2 * (20) *(20) = 400 joules Thermal 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/s Temperature 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 C In 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 Celsius Gravitational 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 distance Converting 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 and Who 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 J Answer • • • • 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 J Mass-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 nucleus Elements • Different elements have different numbers of protons • The properties of an atom are a function of the electrical charge of its nucleus Charge • 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 atom Definitions • 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 neutrons First 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 atom Atoms make up molecules • • • • H2O CO2 CH4 Atoms made up with 2 or more different atoms are called compounds Questions?