Announcements 9/1/10

If you weren’t here on Monday:
a. Read the syllabus ASAP
b. Get notes from other students ASAP
c. Look at website ASAP:
http://www.physics.byu.edu/faculty/colton/courses/phy123fall10/
(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.
b.
c.
d.
e.





Thought question (ungraded):

For a longer canyon behind the dam
(red arrow length), the dam…
a. can be weaker
b. must be stronger
c. 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. yes
b. no
Barometer
(closed)
vacuum
unknown
P2
P1=0
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.
b.
c.
d.
higher
lower
the same
not at all
Reading quiz (graded):

The buoyant force on an object
submerged in water always equals…
a. the weight of the object
b. 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.
b.
c.
d.
lead
steel
wood
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. ironwood
b. walnut
c. same buoyant force
ironwood
walnut
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 gold
b. 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 increases
b. scale reading decreases
c. nothing changes

What will happen to the lower
scale?
a. scale reading increases
b. scale reading decreases
c. 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 rises
b. It falls
c. 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.
b.
c.
d.
e.
It will increase linearly with P0
It will increases quadratically with P0
It will decrease as 1/P0
In will change as log(1+P0)
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.
b.
c.
d.
Overhead transparencies
White board/power point
Don’t care
Might care, but can’t tell yet