Physics 218: MechanicsProf. Rupak MahapatraThe Universe is…Mostly Unknown!Metals (us)∼0 01%Mostly Unknown!Metals (us)∼0.01%Visible Baryons 0.5%Dark Baryons4%4%Dark Matter21%21%Dark Energygy75%Less than 5% of the Universe is Matter as we know it!Less than 1% of Universe is visible!What does the Universe Look Like?It looks hierarchical, contains clusters of galaxies, each galaxy being a cluster of stars and stars having cluster of planets around themStart from the Solar SystemrrGMV)(totalr=Newton’s Law of Gravity describes the motion of planets around Sun wellrMv2GMm‐‐‐‐ = ‐‐‐‐‐‐‐rr2Does this work for Stars in a Galaxy? No!Watch how fast a star rotates around the center…What we think it should look likeWhat it actually looks likeJanuary 2009David Toback, Saturday Morning Physics 5http://bigbang.physics.tamu.edu/Figures/StolenAnimations/galrot_anim.gifRotation of Stars in Spiral GalaxyNewton’s Law applied againMv2GM mv‐‐‐‐ = ‐‐‐‐‐‐‐‐rr2rThe mass M must now grow linearly with distance to explain the non‐dependence of velocity with distanceIf M ∝ Distance r, thenMv2GM r m‐‐‐‐ = ‐‐‐‐‐‐‐‐r r2There is lot more mass than in the galaxyrrMx∝)(There is lot more mass than in the galaxy than the visible stars7Physics 218, Chapter 2A bit about meOut there & may interact on earth!SQUID arrayPhonon AyRshIbiasRfeedbackDCABPhysics 218, Chapter 28QinnerQouterVqbiasCryogenic Dark Matter Search (CDMS)18‐University collaboration Includes TAMU, Stanford, Berkeley, Cal Tech, MIT, etc…Instruments…> $2 millionJoel Sander (Ptd)Kunj Prasad(3rdYear)The TAMU Group(Postdoc)p11Mark Platt (Engineer)Jimmy EricksonKris KochAndrew JastramHomepage http://faculty.physics.tamu.edu/mahapatra/Office: Mitchell Institute 417Phone 845‐8624, email [email protected],p@pyOffice hours:Mon, Wed 10‐12 am or by appointmentTextbook: “Don’t Panic: Volume I”, by William H. Bassichis, 5th EditionGrade Policy• Midterm Exams 50%Lb5%•Lab 5%•Quizzes (including homework quizzes) 5%Fi l40%•Final 40%•You must pass both the lecture(3 midterm exams, final exam, quizzes) and laboratory (>70%) parts of the courseseparately in order to pass the course Grade Policy (cont)•If your grade on the Final Exam is higher than your lowest grade on one of the three exams y ()during the semester, the grade on the Final will replace that one lowest exam grade in computing h d (i ill l ldithe course grade (it will only replace one gradein case of two exams having the same lowest grade)grade). •The Final Exam grade cannotbe used to replace an exam that has been missed without an University excused absence. The missed exam will count as a zero when computing your final grade.All Exams are•Closed book no calculators or notes•Closed book, no calculators or notes •No numbers! In general the problems will beNo numbers! In gener al the problems will be formula solutions with variables• Problems will be similar to those on homework and recitationhomework and recitationMany of you are used to being given formulas and numbers to plug into them…We are not going to do this on the exams! We’ll use variables…If you do the homework the way we ask you to , you’ll be well prepared for the exams!HomeworkYou will have weekly homework assignmentsEvery Recitation, you will have a hw quiz at the beginning of the class with one problem from yourbeginning of the class with one problem from your assignment.Good news: you are allowed to useYOURnotesGood news: you are allow ed to use YOUR notes(no books or photocopies)Check my webpage for hw assignmentsExample for Week 1 (Week Aug 30):Week Aug 30 (due Sep 7): All Chapter 1 problems d iand exercises “D ” th t I’ll i h ith t k“Due” means that I’ll give you a hw quiz that weekH l t t l hkblHowever, please try to solve homework problems even earlier: before your recitations on Monday • Be proactive! Get into it and have fun• Be serious about an old rule of thumb: you have to study 2‐3 hours a week outside the class per each credit hour23 hours a week outside the class per each credit hour• Don’t miss classes (lectures, recitations, labs)• Solve all problems and ex ercises after each Chapter in the book• Don’t fall into the “I understand the concepts but I can’t do the problems” trap. It means you haven’t done enough p p y gof the problems in the chapters.• Every year we have students who think they understand but fail during the examsDon’t let this happen to you!but fail during the exams. Don t let this happen to you!Why study physics?Why study physics?•the most fundamental of the sciencesthe most fundamental of the sciences provides the basis of our understanding of the Universe;Universe;We do want to find out how things work!Provides the basis for all engineeringdisciplinesProvides the basis for all engineering disciplines• scientists of all disciplines make use of the ideas of physicsideas of physics • fun to learn and adventure!New golden age of physicsNew golden age of physicsPuzzles of our Universe:Puzzles of our Universe: acceleration, dark matter, dark energyWd f th lWonders of nanotechnology: man‐made materials with properties on demandEnergy challengeClimate challengeClimate challengeWhat happens when physics is ignored?What happens when physics is ignored?The Royal Warship Vasa capsized on her maiden voyage in August 1628 after sailing less than one mile. Raised in 1961 the Vasa is the only well preserved 17th century warship in the world. She has her own museum inthe world. She has her own museum in Stockholm, Sweden.Vasa was built top‐heavy with insufficient bll tIt b l h h till iballast. It became clear when she was still in the port; however, nobody had the courage to say this to the king. Douglas Isbell Headquarters, Washington, DC Sept. 30, 1999 (Phone: 202/358‐1753) Mar Hardin Jet Prop lsion Laborator Pasadena CA (Phone 818/3545011) JoanNASA PRESS RELEASE 09/30/1999Mary Hardin Jet Propulsion Laboratory, Pasadena, CA (Phone: 818/354‐5011) Joan Underwood Lockheed Martin Astronautics, Denver, CO (Phone: 303/971‐7398) RELEASE 99‐113 MARS CLIMATE ORBITER TEAM FINDS LIKELY CAUSE OF LOSSA failure to recognize and correct an error in a transfer of information between the Mars Climate Orbiter spacecraft team in Colorado and the mission navigation team in California led to the loss of the spacecraft last week
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