Announcements 9/3/10 Any new people? Please see me ASAP. a. Josh Asplund & Justin Liu: you are not officially signed up yet Class directory printouts 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. 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. No homework due Monday either! b. Homework still due tonight! Don’t forget about office hours (low HW scores… low office hour turnout… correlation?) a. Mine today are 2-3 pm (in underground lab) b. TA’s today are 3-4 pm (also in underground lab)
Transcript
Announcements 9/3/10 Any new people? Please see me ASAP.
a. Josh Asplund & Justin Liu: you are not officially signed up yet Class directory printouts
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 lista. 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. No homework due Monday either!b. Homework still due tonight!
a. Mine today are 2-3 pm (in underground lab)b. TA’s today are 3-4 pm (also in underground lab)
Clicker quiz
Which do you prefer?a. (a) White text on black backgroundb. (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.)
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. Be denser than goldb. Be less dense than gold
Reading question (graded):
Which of the following is NOT one of the four assumptions we make when we model “ideal fluids?”
a. The fluid is masslessb. The fluid is nonviscousc. The flow is laminard. The fluid is incompressiblee. The flow is irrotational
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. greater thanb. less thanc. equal to
Quick writing assignment
In the reading assignment for today, Ralph noticed two different equations labeled "Bernoulli's Equation". One said,
P1 + ½ v12 + gh1 = P2 + ½ v2
2 + gh2
whereas the other said, P + ½ v2 + 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?
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. greater thanb. the same asc. less than
The speed on the right will be ____ times the speed on the left.
a. 1/9b. 1/3c. 1d. 3e. 9
Airplane Wings
Principle 1: deflection
Principle 2: Bernoulli
http://www.av8n.com/how/htm/airfoils.html
Curve balls
Ball moving to the right (i.e. air moving to the left), with topspin
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. “float” more than a nonspinning ballb. “sink” faster than a nonspinning ballc. curve to your leftd. curve to your right
