1. Announcements 9/3/10 Any new people? Please see me ASAP. a. a.Josh Asplund & Justin Liu: you are not officially signed up yet Class directory printouts a. a.If you want to be in class directory and missed the signup sheet, I can add you to electronic version. Send me an email. Prayer volunteer list a. a.If you missed the signup sheet, I can add you to the list. Send me an email. Lab 1 starts tomorrow No class on Monday! (Labor Day) a. a.No homework due Monday either! b. b.Homework still due tonight! Don’t forget about office hours (low HW scores… low office hour turnout… correlation?) a. a.Mine today are 2-3 pm (in underground lab) b. b.TA’s today are 3-4 pm (also in underground lab)

2. Clicker quiz Which do you prefer? a. a.(a) White text on black background b. b.(b) Black text on white background This is just a box of fairly random words so that you can get more of a feel for what black text on a white background looks like. (All other slides so far have been the opposite.)

3. Thought question (review): Archimedes was charged with determining if a crown was pure gold. One method he may have used: suppose he balanced the crown with pure gold outside water. After immersing, the balance tipped as shown. The crown must: a. a.Be denser than gold b. b.Be less dense than gold

4. Reading question (graded): Which of the following is NOT one of the four assumptions we make when we model “ideal fluids?” a. a.The fluid is massless b. b.The fluid is nonviscous c. c.The flow is laminar d. d.The fluid is incompressible e. e.The flow is irrotational http://www.youtube.com/watch?v=W3YZ5veN_Bg

5. Reading quiz (graded): Water flows from a pipe with large diameter into a pipe with smaller diameter. The speed of the water in the small tube will be _________ the speed in the large tube. a. a.greater than b. b.less than c. c.equal to

6. Quick writing assignment In the reading assignment for today, Ralph noticed two different equations labeled "Bernoulli's Equation". One said, P 1 + ½  v 1 2 +  gh 1 = P 2 + ½  v 2 2 +  gh 2 whereas the other said, P + ½  v 2 +  gh = constant He asks you how they can both be the same equation when they look so different? And what it’s the value of the constant in the second equation, anyway? What should you tell him?

7. Thought questions (ungraded): Water flows from the little pipe into the big pipe. Ignore any friction or height change. The volume flow rate on the right will be ______ on the left a. a.greater than b. b.the same as c. c.less than The speed on the right will be ____ times the speed on the left. a. a.1/9 b. b.1/3 c. c.1 d. d.3 e. e.9

8. Airplane Wings Principle 1: deflection Principle 2: Bernoulli http://www.av8n.com/how/htm/airfoils.html

9. Curve balls Ball moving to the right (i.e. air moving to the left), with topspin

10. Thought question: A ball is thrown toward you, spinning so that (as you look at it) the right side of the ball spins toward you, and the left side away. The ball will a. a.“float” more than a nonspinning ball b. b.“sink” faster than a nonspinning ball c. c.curve to your left d. d.curve to your right