1. Astronomy 100 Tuesday, Thursday 2:30 - 3:45 pm Tom Burbine tburbine@mtholyoke.edu www.xanga.com/astronomy100

2. Help Desk There is an Astronomy Help Desk in HAS 205. It will be open from Monday through Thursday from 7-9 pm.

3. 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

4. The Test The average was 71.5% (28.6 out of 40) Grades ranged 12 to 39

5. 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.

7. 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 13 th constellation was added to the zodiac

10. Long Term Changes

11. Since most people did not seem enjoy the test?

12. Another Homework Assignment (Due Thursday March 3 rd ) 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

13. 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

14. 2 nd 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

15. Matter Matter is material

16. 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

18. 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

19. Kinetic energy Kinetic energy = ½ mv 2 m is mass in kg v is velocity in meters/s A joule has units of kg-m 2 /s 2

20. PRS question #1 How much energy does a 2 kg rock have if it is thrown at 20 m/s? Kinetic energy = ½ mv 2 A) 200 J B) 400 J C) 40 J D) 800 J

21. Answer KE = ½ * 2 * (20) *(20) = 400 joules

22. 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

23. 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

24. 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

26. 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

27. Converting Mass to Energy What is the most famous formula in the world?

28. E = mc 2 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

29. Who came up with it?

31. PRS question #2 How much energy can be produced if you can convert 10 kg of material in energy? E = mc 2 A) 3.0 x 10 8 J B) 3.0 x 10 16 J C) 9.0 x 10 17 J D) 9.0 x 10 10 J

32. Answer E = 10 kg * (3 x 10 8 m/s) * (3 x 10 8 m/s) E = 10* (9 x 10 16 ) J E = 90 x 10 16 J E = 9.0 x 10 17 J

33. Mass-Energy So Mass is a form of potential energy Where is one place where you see mass converted into energy?

35. 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

38. Elements Different elements have different numbers of protons The properties of an atom are a function of the electrical charge of its nucleus

39. 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

41. Definitions Atomic Number – Number of protons Atomic Mass – Number of protons and neutrons U 235 – atomic mass 92- atomic number Isotopes – Same number of protons but different numbers of neutrons

42. 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

43. Atoms make up molecules H 2 O CO 2 CH 4 Atoms made up with 2 or more different atoms are called compounds

45. Questions?