- What is happening to the outside air pressure today?
- If we wet the inside of a bell
jar, add some smoke, and then pump the air out of the jar using a vacuum
pump, will a cloud form inside the jar?
- A "front" is where two different air masses meet. Cold
fronts and warm fronts have different shapes, which cause them to
produce different types of weather events. Both bring
precipitation, but one brings more intense precipitation. Look
at the picture on the board... Which front will produce more intense
precipitation? Why are they shaped differently -- isn't warm
air hitting cold air the same thing as cold air hitting warm air????
- Block 1: Complete Weather/Climate Questions 1-14.
- Block 2: Complete North America Climate Map and Practice
I. The diagram on the right shows a simple
- If A is the position of a compressor, and B is
the position of an expansion valve, which way should the fluid flow?
Clockwise or counter-clockwise?
- Where should the drip pan be located? At C,
D, or E? Why?
- Why is it a problem for the refrigerant to flow
in the opposite direction?
- As air rises, which type of air cools off faster,
dry air (low relative humidity) or wet air (100% relative humidity)?
- All other things being equal, which air is more
dense, air with low or high relative humidity?
III. The How can you get a boiled egg to fit
through the neck of a narrow mouthed glass flask?
- Complete climate maps of practice continents A and B.
- Quiz next class: be able to draw climate maps on continents
such as A and B.
Block 2: None
Explanatory test videos:
"This I Believe" essay by Jon Carroll
The diagram on the right shows a simple refrigerator.
Arrows indicated the direction of "refrigerant" flow through a tube. The
positions of a compressor and an expansion valve are indicated as
- At which letter is the expansion valve located?
- At which letter is the compressor located?
- Why does the refrigerant meander?
- What makes a good refrigerant?
1. How do home canning jars work?
2. The plume of "smoke" below is mostly water.
Is that water probably a solid, liquid, or a gas?
- If you have colored pencils, bring them to class on Monday.
- Why does human skin tend to become drier in the
- Why are basements more damp in the summer?
- What is climate?
- How can you create over 100 smoke rings by using
six playing cards and by blowing out just one birthday candle?
It is often the
case that a cork floating in a narrow glass jar will "want" to move to
the side of the jar. Without touching the cork, how can you make
it stay in the middle of the jar? [There are at least two simple
- Check and discuss pressure review part I. Below is a video
of 2nd block discussion of #1-10 and the last one. In my
discussion of the helmet question, I started into an example that
I'm afraid might have left some of you more confused than you were
Here's a simple way to look at the helmet question... Imagine that
your head is made of snow. If you have to allow tiny people to
walk around on it, would you prefer that they wear boots or
snowshoes? The smart answer is snowshoes, because snowshoes
will decrease the pressure applied by your
pedestrians. The pedestrians' force remains the same, but it
is spread over a larger area. Likewise, a helmet -- even a
hard one -- spreads out the force of impact and lessens the
possibility of skull penetration.
- Questions about the problems???
- Begin short unit: using physics to understand weather and deduce
- Test next Thursday. Questions will be selected from the
test review questions and problems.
Hank and Bertha are
sitting on a merry-go-round that is rotating counter-clockwise.
They begin throwing things at one-another while the merry-go-round
continues to turn.
The Coriolis Effect can cause thrown objects to appear
to curve as they leave the thrower. As Hank and Bertha throw their
projectiles, who sees her/his projectiles curve to the right? Who sees
his/her projectiles curve to the left? Who sees no curve?
- Check for homework
Blank template for #16
- Hovercraft Stuff: Create a graph of coefficient of
friction vs. payload. Attempt a perfect hovercraft stop.
Coriolis simulation -- hopefully.
- We used an "air source" to inflate hot air
balloons and thereby measure their volumes. How can we
determine the gauge pressure produced by that air source?
- Can we use the air source and a heavy duty trash
bag to lift a student? Why or why not?
- Can you think of three different equations (with
none of the same variables) for pressure? [Think of a third one may
- Questions about the pressure problems?
- Explanation of homework -- particularly 16
Hovercraft Questions and experimentation
- Work time -- homework, excel
Homework: Due on Monday
- Complete "more pressure problems" 13, 14, and 16-18. You
can skip 15.
Video Explanations of "More Pressure
- How does siphoning
- Can you siphon without gravity? What about
without an atmosphere?
- What's a water level?
How does it work?
- Problems 8b-12.
- Mini-hovercrafts -- modify for maximum distance.
- Block 1: Watch video of solutions to homework problems.
- Due next Thursday -- Problem #16 -- graph of liftable mass
vs spherical balloon radius.
A lot of igloos end
up looking more
like castles; their walls are too vertical to form a dome. Can you
think of a "fool-proof" way to build an actual dome?
Link to igloo
- BHS Arts Festival May 27th
- Check for homework problems that were due on 2/11. Review Problems.
Here are the solutions to ALL of the problems, including the missing
parts of 8a and 8b. See below for video solution.
You will need to view this on full screen. And if you have an
HD monitor, make sure you turn it on in the video.
- Work time -- Balloon calculations
- Complete balloon calculations. Enter solutions into
so that Mr. Stapleton can easily check your answers. Fill in all of the blanks.
sledding video with soundtrack.
What does the
Gateway Arch have in common with a really, really, strong igloo -- but
a bad ski jumper?
- Get balloons flying. Collect data -- either mass lifted or
reduction of felt mass.
- Enter your data into this
Excel spreadsheet. Fill in all of the blanks.
Complete balloon calculations. Enter into Excel Spreadsheet,
above, and turn in by Friday after break (March 4th)
What do a good
igloo and a bad ski jumper have in common?
See last class
- What's the opposite of a suction cup?
- What's the principle that makes snowshoes work?
- Why are longer skis generally faster?
- Ho much pressure can you generate?
- Work time: problems and/or balloons
- Balloons must be "flown" by the end of class next Thursday.
- Next class -- something in the snow.
1. Bring snow attire next class.
2. Balloons must be "flown" by the end of class next Thursday. For an A+ on this project, you must
use buoyancy to correctly calculate the air temperature inside your bag.
These calculations must be done individually, but you may get some
help from your friends. If your balloon actually flies on its
own, you get an extra 2% added to your grade. If groups would like
to fuse their balloons together, that is okay.
Problems 1-6, 8-12.
are my solutions. I haven't double checked them, so there may
be some mistakes.
- The molar mass of dry ice is about 44g/mol.
If a chunk of dry ice is placed in a 2-liter bottle, and then the
bottle is capped, the bottle can explode as the dry ice sublimes
(solid to vapor). At 70 degrees Fahrenheit (294.3K),
approximately how much dry ice would have to sublime in order for
the bottle to explode? Assume that a two-liter bottle can
withstand exactly 180psi of internal pressure. Consider the
volume of the solid dry ice to be negligible.
- Is this estimate probably a little low or a
little high? Explain.
- What are some of the dangers of doing this?
Homework: Generate at
least two proposals regarding how we can incorporate the snow into this
class. E-mail them to
- I have two balloons separated by a closed tube.
One is almost fully inflated. One is just partially inflated.
What will happen when air is allowed to
flow through the tube?
- What's the easiest way you can think of to
accurately measure the air pressure inside a balloon?
- Review homework. See video below. The other one
should be posted by tomorrow.
Homework Problems 12-14. Time-saving, corner-cutting change to
#14**** -- Assume that the steel sheets from which the boat is
made have a mass/area ratio of 234kg/m^2, and also assume that they have
- In pounds, how much heavier would you be if this
room were a vacuum?
- Fred put a flat, empty Ziploc bag on a super
sensitive balance and recorded the bag's mass. Fred then
opened the bag, filled it half-way with room air, sealed it, and
placed it back on the balance. When Fred checked the new mass
reading, did he see an increase, a decrease, or no change?
- A 40ml rock has a density of 7g/ml. The rock is placed inside a
1 liter Ziploc plastic bag having an empty mass of 10g. The rest
of the bag is filled completely with air having a density of
1.2kg/m^3 and a pressure equal to the outside air pressure
(101,350pa). The bag is sealed in this state. The bag is then
attached to the outside of a submarine and carried downward until
the bag begins to sink on its own. If the bag remains intact and
loses none of its contents, at what water depth does it begin to
sink on its own? Assume that the volume of the plastic in the bag
is negligible and that there is no significant temperature change
with water depth.
- You place an empty balloon on a balance, and the balloon's mass
is 15g. Then you inflate the balloon with dry air and measure
the balloon's new total mass. The new mass is 16g.
You know that the balloon's volume is 5L, and you know that the
current density of the room air is 1.2kg/m^3. If the air
pressure is 101,350pa, and there is no temperature change, what is the gauge pressure
of the air inside the
balloon, in psi? ["gauge pressure" is pressure minus atmospheric
Each of the
graduated cylinders contains the same amount of water. Find the
volumes, masses, and densities of objects A and B.
You would have already tried this, had your bathtub and tub toys been
The pictures on the right show a person holding a
very long glass test tube. In picture A, the tube is essentially
full of air, though it is leaking a few bubbles from the bottom (because
the picture looks more fun that way). The tube is sealed on its
In picture B, the person has somehow filled the test tube with water
and submerged it. The tube is being raised from the water, closed
Regarding picture B, if you assume that the tube is 500m long, what
will happen to the water level inside the tube as the tube is held
vertically and its closed end is raised 499m above the water's surface?
If 1inHg = 3386pa, what's the density of mercury?
- Attempted Fire Demo
- Scuba Demo
- Hot Air Balloon Practice problem... Find the
Fahrenheit temperature inside this hot air
balloon... The balloon's volume is 0.4m^3. The total
mass of the empty balloon is 0.058kg. At its maximum buoyancy,
the balloon has lifted itself, plus 30cm of rope. Each cm of
this rope has a mass of 0.0015kg. Current air pressure is
29.92inHg. 1inHg = 3386pa. Assume that the molar mass of
air is 28.97g/mol.
Givens are in yellow. Steps are black. Solution is in
- Complete pressure questions and problems 1-7, 11
- For more help, read p.275-286 in the textbook.
- Explain (in detail) why the blobs in a lava lamp rise and sink.
- I have a film canister with a hole in the lid, some Alka
Seltzer, some pennies, and a vessel full of water. Explain how
to make the canister sink to the bottom, sit there for a while, and
then rise back to the surface on its own?
- Return Midterms
- Block 2: Finish notes [Link
to completed notes.
- Problem: density of plumber's putty. Find
the density of plumbers' putty using water, liquid measurement
containers, and plumbers' putty.
- Collect materials for hot air balloon -- due next class.
- pressure questions and problems 1-7, 9, 11-13