1. Announcements 9/1/10 If you weren’t here on Monday: a. a.Read the syllabus ASAP b. b.Get notes from other students ASAP c. c.Look at website ASAP: http://www.physics.byu.edu/faculty/colton/courses/phy123- fall10/ (especially the “How to get started” section) Signup sheets to pass around again Anyone not officially registered for this section? The first homework assignment is due tonight!

2. Foxtrot, by Bill Amend

3. Reading quiz (graded): (Review) The symbol for density used by your textbook–and by nearly all physicists–is: a. a.  b. b.  c. c. d. d.  e. e. 

4. Thought question (ungraded): For a longer canyon behind the dam (red arrow length), the dam… a. a.can be weaker b. b.must be stronger c. c.can be the same

5. Reading quiz (graded): Ralph measures the pressure in his flat tire with a standard automotive pressure gauge. The gauge reads zero. Is the pressure inside the tire 0 atm? a. a.yes b. b.no

6. Barometer unknown P 2 P 1 =0 (closed) vacuum

7. Thought question (ungraded): On the moon, where gravity is less but there is no atmosphere, if you pump out the air at the top of a barometer, the mercury would rise ________ compared to on earth. a. a.higher b. b.lower c. c.the same d. d.not at all

8. Reading quiz (graded): The buoyant force on an object submerged in water always equals… a. a.the weight of the object b. b.the net force on the object c. c.the weight of the water that would otherwise occupy the object's space

9. Thought question: Three cubes of the same size and shape are put in water. They sink. One is lead, one is steel and one is a dense wood (ironwood).  lead >  steel >  ironwood. The bouyant force is greatest on the _______ cube a. a.lead b. b.steel c. c.wood d. d.same buoyant force

10. Thought question: Two cubes of the same size and shape are made out of wood. The ironwood cube sinks, but the walnut cube floats. The bouyant force is greatest on the _______ cube a. a.ironwood b. b.walnut c. c.same buoyant force ironwood walnut

11. Thought question: 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

12. Thought questions: In the demo, what will happen to the upper scale when the mass is submerged. a. a.scale reading increases b. b.scale reading decreases c. c.nothing changes What will happen to the lower scale? a. a.scale reading increases b. b.scale reading decreases c. c.nothing changes

13. Thought question: A cannonball is in a boat, which is in the middle of a small lake. (Frictionless, wave-less, etc.) A person tosses the cannonball from the boat into the lake. What happens to the overall water level of the lake (where the water touches the shore)? a. a.It rises b. b.It falls c. c.It stays the same

14. Thought question: How will the buoyant force on a submerged object change with P 0, the air pressure above the water? a. a.It will increase linearly with P 0 b. b.It will increases quadratically with P 0 c. c.It will decrease as 1/P 0 d. d.In will change as log(1+P 0 ) e. e.It will not change

15. Thought question: Do you prefer overhead transparencies like Monday or white board (and PowerPoint for quiz/thought questions) like today? a. a.Overhead transparencies b. b.White board/power point c. c.Don’t care d. d.Might care, but can’t tell yet