Announcements 9/1/10

If you weren’t here on Monday:a. Read the syllabus ASAPb. Get notes from other students ASAPc. 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!

Foxtrot, by Bill Amend

Reading quiz (graded):

(Review) The symbol for density used by your textbook–and by nearly all physicists–is:

a. a b. c. . e.

Thought question (ungraded):

For a longer canyon behind the dam (red arrow length), the dam…

a. can be weakerb. must be strongerc. can be the same

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. yesb. no

Barometer

unknown P2

P1=0

(closed)

vacuum

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. higherb. lowerc. the samed. not at all

Reading quiz (graded):

The buoyant force on an object submerged in water always equals…

a. the weight of the objectb. the net force on the object c. the weight of the water that would

otherwise occupy the object's space

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. leadb. steel c. woodd. same buoyant force

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. ironwoodb. walnut c. same buoyant force

ironwoodwalnut

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. Be denser than goldb. Be less dense than gold

Thought questions: In the demo, what will happen

to the upper scale when the mass is submerged.

a. scale reading increasesb. scale reading decreasesc. nothing changes

What will happen to the lower scale?

a. scale reading increasesb. scale reading decreasesc. nothing changes

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. It risesb. It fallsc. It stays the same

Thought question:

How will the buoyant force on a submerged object change with P0, the air pressure above the water?

a. It will increase linearly with P0

b. It will increases quadratically with P0

c. It will decrease as 1/P0

d. In will change as log(1+P0)

e. It will not change

Thought question:

Do you prefer overhead transparencies like Monday or white board (and PowerPoint for quiz/thought questions) like today?

a. Overhead transparenciesb. White board/power pointc. Don’t cared. Might care, but can’t tell yet