Fred Schaal [Lane Tech HS,
Mathematics]
Afterburner Bike Rides
Fred had just taken advantage of 30 knot winds
to the South, in
riding his bike on the bike path along Lake Michigan, on the way to our
class. A month ago he encountered a serious sand blizzard
on that
route because of the high winds -- but not this time! Fred showed
off his flashing red LED bike tail light with a "bulldog clip".
Also, he showed a flashing headlight that contained LEDs.
Don
Kanner mentioned that the Inch Gear on a bicycle is
defined as the
diameter of the drive wheel (in inches) multiplied by the mechanical
advantage
of the gearing system. Believe it or not! For
details see the
website The Bicycle Gear: How It Works for us:
http://www.sobjoy.com/gears.html.
Fred also
mentioned the full moon tonight, with the summer triangle (and
little else)
visible in the sky. Thanks, and enjoy the monsters, Fred.
Betty
Roombos [Gordon Tech HS,
Physics]
Constant
Speed Buggy
Betty found a very nice Constant Speed Motion Car in a Science
Kit catalog: http://www.sciencekit.com/store/catalog/product.jsp?catalog_number=166438
[cost $7.50, requires 2 C-cell batteries. After she
obtained
the car, she tested it and found that it traveled at a rather constant
speed -- true
to its name. We found that it moved across our classroom floor in
a rather
straight path with a speed of 40 cm/sec. Very nice! We
also
noticed that, when the car ran into the front wall the front wheels
climbed up
the wall. The car flipped end-over-end, and went back to in the
opposite direction. The car was
smart, as well
as reliable! Betty gave us a handout describing the Constant
Speed Experiment for her students, which used a Pasco Recording
Timer
that produced dots at constant time intervals on a strip of recording
tape
attached to the car. Her students constructed graphs of distance vs
time
and speed vs time to test for uniform speed. Now, that's a
hot car!
Thanks, Betty!
Larry Alofs [Kenwood HS,
Physics]
The First Motion Graph
Larry brought in a small battery operated car that he obtained
some
time ago at American Science & Surplus [http://www.sciplus.com/],
but which is no longer available. The car operated at two
speeds --
we tested it on the table at the lower speed. Taking averages
with two
trials and four stopwatches provided by Larry, we obtained the
following
set of data for distance traveled versus time.
Distance (cm) | Time (sec) |
0 | 0.0 |
25 | 1.20 |
50 | 2.40 |
75 | 3.56 |
Debbie Lojkutz [Joliet West HS,
Physics]
Studying Straight Line Motion with a Ticker Tape Timer
Debbie described the following experiments that involve
linear
motion:
Number | Experiment | Category |
1 | Stomper Car | Speed 1 ---> Speed 2 |
2 | Car Rolling down Ramp | Uniform Acceleration (slow) |
3 | Free Fall | Uniform Acceleration (fast) |
4 | Chain Sliding off Table | Variable Acceleration |
5 | Pendulum | Simple Harmonic Motion |
Lab 2.3: Motion of a PendulumDebbie also reminded us of the chart she and Ann Brandon have long used to describe determining the Displacement, Velocity, and Acceleration, from graphs of Displacement vs Time, Velocity vs Time, and Acceleration vs Time; respectively. That chart is described in detail in the HS Mathematics-Physics SMILE lesson of 24 September 2002: mp092402.html . Very nice, Debbie!Purpose: To Investigate the relationships among Distance and Time, and Velocity and Time for a one-way swing (1/2 period) of a Pendulum.
Procedure:
Analysis:
- Set up the pendulum with a length of about 2 meters, so that it just misses the ground as it swings.
- You will need about 2 meters of ticker tape.
- Thread the ticker tape through the timer.
- Place the timer on the ground, about 1 meter from the bottom of the swing.
- Pull the mass over to the timer, and attach the ticker tape to the mass.
- Turn on the timer. Let go of the mass. Have your partner catch it on the other side, JUST as it starts to swing back.
Questions:
- Mark every 6th dot on the tape.
- Measure the distance from the start of the tape to each 6th dot mark, and record in your data table.
- Calculate DD, DT, and V, recording in your data table.
- Graph D vs T, and V vs T.
- On the D vs T graph, mark the positions of Zero Velocity and the Maximum Velocity.
Conclusion:
- What is the average velocity of the pendulum for the one-way swing?
- What is the average acceleration of the pendulum for the one-way swing?
- What is the period of a complete cycle of the pendulum?
- What is the maximum velocity of the pendulum?
- What is the acceleration of the pendulum at the beginning of the swing?
- What is the acceleration of the pendulum at the end of the swing?
- Look at the graphs. Describe each of them.
- Is the V vs T graph symmetrical?
What does this indicate about the velocities at either end of the swing?
What does this indicate about the accelerations at either end of the swing?
Don Kanner [Lane Tech HS,
Physics]
A Quick Graph
Don described a quick way to get rather accurate data of a
falling
object, by dropping that object alongside a vertical meter stick, and
recording
the fall with a video camera. Using the "freeze frame"
display feature, the position of the top of the the falling object is
recorded
at a rate of 30 frames per second. You just read the data
directly
off the image, and then draw the graph. Neato! Porter
Johnson mentioned that a bucket dropped into the hand-dug well over
100
meters in depth at the Hohenzollern
Medieval Castle in Nuremberg, Germany took 5-6 seconds
to hit
the water level -- kerplunk! The Tiefer Brun
(deep well)
was essential for defending the castle during times of siege! For
details see the website
http://www.oldandsold.com/articles13/travel-125.shtml.
Thanks for sharing this, Don!
Charlotte Wood-Harrington [Gwendolyn Brooks HS,
Physics]
The Physics of Guinness Stout (Let's Party!)
Charlotte felt that it was more direct to ask for forgiveness
(afterward) than to seek permission (before), in presenting a
lesson on the
behavior of bubbles in a properly poured glass of the scintillating
Irish brew
mentioned above. She told us that the small bubbles near the
outside edge of the
glass actually fall, whereas the larger bubbles near the center of the
glass
rise. For purely scientific purposes, she
demonstrated the effect by
slowly pouring the beverage into the side of a glass. We saw
the
bubbles on the outside fall! But, how come?
Charlotte
claimed that the essential item was a small widget that
had been strategically
placed inside the can by the manufacturer. She tore the can apart and
showed us
the widget -- a ball about 1 inch (2 cm) in diameter
filled with Nitrogen
gas. See the website: How Does a Widget in a Beer
Can Work?
http://home.howstuffworks.com/question446.htm.
Charlotte showed us that an Alka-Seltzer® tablet
placed into a glass of water would produce the same effect. For more
details
also see Do bubbles in Guinness
go down?
http://www.stanford.edu/group/Zarelab/guinness/why.html.
Charlotte recommended that we should consider celebrating day number 10,000 or 20,000 on this earth. She ran an EXCEL® program that would calculate the number of days since the specified date of birth. For example, a random person born on 23 May 1926 has been on this earth for 28,618 days. In a few years, that person could celebrate day number 30,000! What a great idea for a party!
Finally, Charlotte informed us that Chicken McNuggets® may be ordered at McDonalds™ Restaurants in quantities of 6, 9, and 20 per package. What is the largest number of Chicken McNuggets that is impossible to order at McDonalds? Hint: apply ternary logic, but observe that the answer is not "42", since 6 ´ 7 = 42 --- apologies to A Hitchhiker's Guide to the Galaxy by Douglas Adams [See The issue of the "42": http://en.wikipedia.org/wiki/The_Hitchhiker%27s_Guide_to_the_Galaxy].
Thanks for the ideas, Charlotte!
Notes prepared by Porter Johnson