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PHY 113 C General Physics I 11 AM-12:15 P M MWF Olin 101 Plan for Lecture 9: Review (Chapters 1-8) E xam preparation

PHY 113 C General Physics I 11 AM-12:15 P M MWF Olin 101 Plan for Lecture 9: Review (Chapters 1-8) E xam preparation advice – Example problems. iclicker question What is the best way to prepare for Thursday’s exam?

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PHY 113 C General Physics I 11 AM-12:15 P M MWF Olin 101 Plan for Lecture 9: Review (Chapters 1-8) E xam preparation

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  1. PHY 113 C General Physics I • 11 AM-12:15 PM MWF Olin 101 • Plan for Lecture 9: • Review (Chapters 1-8) • Exam preparation advice – • Example problems PHY 113 C Fall 2013-- Lecture 9

  2. PHY 113 C Fall 2013-- Lecture 9

  3. iclicker question • What is the best way to prepare for Thursday’s exam? • Read Lecture Notes and also reread Chapters 1-8 in Serway and Jewett. • Prepare equation sheet. • Solve problems from previous exams. • Solve homework assignments (both graded and ungraded) from Webassign Assignments 1-8 • All the above PHY 113 C Fall 2013-- Lecture 9

  4. iclicker question • Have you (yet) accessed the online class lecture notes from previous classes? • yes • no • iclicker question • Have you (yet) accessed the passed Webassign Assignments (with or without the answer key)? • yes • no PHY 113 C Fall 2013-- Lecture 9

  5. Access to previous exams PHY 113 C Fall 2013-- Lecture 9

  6. Previous exam access -- continued Overlap with 2013 schedule PHY 113 C Fall 2013-- Lecture 9

  7. Comments on preparation for next Thursday’s exam – continued • What you should bring to the exam (in addition to your well-rested brain): • A pencil or pen • Your calculator • An 8.5”x11” sheet of paper with your favorite equations (to be turned in together with the exam) • What you should NOT use during the exam • Electronic devices (cell phone, laptop, etc.) • Your textbook PHY 113 C Fall 2013-- Lecture 9

  8. Problem solving skills Equation Sheet Math skills • Advice: • Keep basic concepts and equations at the top of your head. • Practice problem solving and math skills • Develop an equation sheet that you can consult. PHY 113 C Fall 2013-- Lecture 9

  9. iclicker exercise • Does the previous slide annoy you? • yes • no PHY 113 C Fall 2013-- Lecture 9

  10. Problem solving steps • Visualize problem – labeling variables • Determine which basic physical principle(s) apply • Write down the appropriate equations using the variables defined in step 1. • Check whether you have the correct amount of information to solve the problem (same number of knowns and unknowns). • Solve the equations. • Check whether your answer makes sense (units, order of magnitude, etc.). PHY 113 C Fall 2013-- Lecture 9

  11. Likely exam format (example from previous exam) PHY 113 C Fall 2013-- Lecture 9

  12. Likely exam format (example from previous exam) PHY 113 C Fall 2013-- Lecture 9

  13. Review of slides from previous lectures PHY 113 C Fall 2013-- Lecture 9

  14. Mathematics Review -- Appendix B Serwey & Jewett c a q b PHY 113 C Fall 2013-- Lecture 9

  15. One dimensional motion --Summary of relationships PHY 113 C Fall 2013-- Lecture 9

  16. Special relationships between t,x,v,a for constant a: PHY 113 C Fall 2013-- Lecture 9

  17. Introduction of vectors Vector addition: a + b b a Vector subtraction: a a – b -b PHY 113 C Fall 2013-- Lecture 9

  18. Treatment of vectors in component form by bx ay ax PHY 113 C Fall 2013-- Lecture 9

  19. Vectors relevant to motion in two dimenstions Displacement: r(t) = x(t) i + y(t) j Velocity: v(t) = vx(t) i + vy(t) j Acceleration: a(t) = ax(t) i + ay(t) j PHY 113 C Fall 2013-- Lecture 9

  20. Visualization of the position vector r(t) of a particle r(t2) r(t1) PHY 113 C Fall 2013-- Lecture 9

  21. Visualization of the velocity vector v(t) of a particle v(t) r(t2) r(t1) PHY 113 C Fall 2013-- Lecture 9

  22. Visualization of the acceleration vector a(t) of a particle v(t2) v(t1) r(t2) r(t1) a(t1) PHY 113 C Fall 2013-- Lecture 9

  23. j vertical direction (up) Projectile motion (near earth’s surface) g = 9.8 m/s2 horizontal direction i PHY 113 C Fall 2013-- Lecture 9

  24. Projectile motion (near earth’s surface) PHY 113 C Fall 2013-- Lecture 9

  25. Projectile motion (near earth’s surface) Trajectory equation in vector form: Trajectory equation in component form: Aside: The equations for position and velocity written in this way are call “parametric” equations. They are related to each other through the time parameter. PHY 113 C Fall 2013-- Lecture 9

  26. Diagram of various trajectories reaching the same height h=1 m: y q x PHY 113 C Fall 2013-- Lecture 9

  27. Projectile motion (near earth’s surface) Trajectory equation in component form: Trajectory path y(x); eliminating tfrom the equations: PHY 113 C Fall 2013-- Lecture 9

  28. Isaac Newton, English physicist and mathematician (1642—1727) In the absence of a net force, an object remains at constant velocity or at rest. In the presence of a net force F, the motion of an object of mass m is described by the form F=ma. F12 =– F21. http://www.newton.ac.uk/newton.html PHY 113 C Fall 2013-- Lecture 9

  29. Newton’s second law F = m a Types of forces: FundamentalApproximateEmpirical Gravitational F=-mg j Friction Electrical Support Magnetic Elastic Elementary particles PHY 113 C Fall 2013-- Lecture 9

  30. Example of two dimensional motion on a frictionless horizontal surface m PHY 113 C Fall 2013-- Lecture 9

  31. Example – support forces Fsupport acts in direction  to surface (in direction of surface “normal”) PHY 113 C Fall 2013-- Lecture 9

  32. Example of forces in equilibrium PHY 113 C Fall 2013-- Lecture 9

  33. Example: 2-dimensional forces • A car of mass m is on an icy (frictionless) driveway, inclined at an angle t as shown. Determine its acceleration. Conveniently tilted coordinate system: PHY 113 C Fall 2013-- Lecture 9

  34. Another example: Note: we are using a tilted coordinate frame i vf=0 vi mg mg sin q PHY 113 C Fall 2013-- Lecture 9

  35. Friction forces The term “friction” is used to describe the category of forces that oppose motion. One example is surface friction which acts on two touching solid objects. Another example is air friction. There are several reasonable models to quantify these phenomena. Surface friction: Normal force between surfaces Material-dependent coefficient Air friction: K and K’ are materials and shape dependent constants PHY 113 C Fall 2013-- Lecture 9

  36. Models of surface friction forces surface friction force fs,max=msn (applied force) Coefficients ms ,mkdepend on the surfaces; usually, ms>mk PHY 113 C Fall 2013-- Lecture 9

  37. Consider a stationary block on an incline: n f mg cosq mg mg sin q q q PHY 113 C Fall 2013-- Lecture 9

  38. Consider a block sliding down an inclined surface; constant velocity case n f=mkn V (constant) mg q PHY 113 C Fall 2013-- Lecture 9

  39. Summary n f mg cosq mg mg sin q q q PHY 113 C Fall 2013-- Lecture 9

  40. Uniform circular motion and Newton’s second law r PHY 113 C Fall 2013-- Lecture 9

  41. Definition of work: F dr ri rj PHY 113 C Fall 2013-- Lecture 9

  42. Example: PHY 113 C Fall 2013-- Lecture 9

  43. Work and potential energy Note: It is assumed that F is conservative PHY 113 C Fall 2013-- Lecture 9

  44. Review of energy concepts: PHY 113 C Fall 2013-- Lecture 9

  45. Summary of work, potential energy, kinetic energy relationships PHY 113 C Fall 2013-- Lecture 9

  46. Example problem from Webassign #8 A baseball outfielder throws a 0.150-kg baseball at a speed of 37.2 m/s and an initial angle of 31.0°. What is the kinetic energy of the baseball at the highest point of its trajectory? vf yf vi qi PHY 113 C Fall 2013-- Lecture 9

  47. Example problem from Webassign #8 The coefficient of friction between the block of mass m1 = 3.00 kg and the surface in the figure below is μk = 0.440. The system starts from rest. What is the speed of the ball of mass m2 = 5.00 kg when it has fallen a distance h = 1.85 m? f h h PHY 113 C Fall 2013-- Lecture 9

  48. Example problem from Webassign #8 A block of mass m = 3.40 kg is released from rest from point A and slides on the frictionless track shown in the figure below. (Let ha = 6.70 m.) . PHY 113 C Fall 2013-- Lecture 9

  49. Example problem from 2012 Exam #2: PHY 113 C Fall 2013-- Lecture 9

  50. Example problem from Webassign #5 PHY 113 C Fall 2013-- Lecture 9

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