05 September 2000

Notes Prepared by Earl Zwicker

**Bill Colson (Morgan Park HS)**

treated us to a classic bit: Tom Lehrer's "New Math" playing out a neat
pair of speakers and radio-recorder-player. Entertaining
and somewhat informative perspective.

**Ann Brandon (Joliet West HS)**
gave each group of two of us an eye dropper and a __dixie cup__
half-filled with water. We provided our own penny, and Ann told us
to find out how many drops of water the penny would hold. She
posted results on the board as we found our answers:

Heads | 22 | 21 | 30 | 34 | 24 | 28 | 13 | 17 |

Tails | 28 | 45 | 30 | 31 | 24 | 18 |

In our curiosity to explain the results, the concepts of area and surface tension were brought up and discussed, and we enjoyed a good review and multiple insights into these topics. A good classroom investigation - Thanks, Ann!

**Don Kanner (Lane Tech HS)**

showed us Galileo's inclined plane experiment. Galileo used a source
of water drops as a clock (equal time intervals between drips) in
order to time how long it took for an object to move down
a plane inclined at a measured angle above the vertical.
To have calibrate elapsed time, one would measure the
amount of water collected in 10 seconds. One would do this
for increasing angles of inclination, and make a graph of
acceleration down the plane vs angle of inclination. As
the angle approaches 90 deg (ie, vertical), the
acceleration would approach that of an object in free
fall, the acceleration due to gravity, which can be
inferred from extrapolation on the graph. The inclined
plane, in a sense, "dilutes" the acceleration due to
gravity so that motion may be measured over the long time
intervals available on a water clock of that era. Great
ideas! Thanks, Don!

**Fred Schaal (Lane Tech HS)**

told us to look due East about one hour before sunrise, and observe
the sky. Watch the planets in the pre-dawn sky! They form a
triangle: Saturn, Jupiter, and **?? (Do you know?)** The
beauty and pleasure of astronomy. Thanks, Fred!

**Bill Blunk (Joliet Central HS)**

showed us the **Orbitron magnetic toy**. (Manufactured by Binary
Arts, and
available at the website of The Toy Box:
http://www.toyboxligonier.com/tbx/orbitron.html.
See also the **Wizmo Orbitron**, available at
http://www.parents-choice.org/product.cfm?product_id=1839&award=xx&from=ThinkFun).
Essentially, it was made with two chrome-plated heavy wire
rings, of equal diameter (about 27 cm), held coaxially a
fixed distance apart (by a frame of some sort). A small
but massive metal top had magnetized axles, which held it
onto the pair of rings.

If the rings were held with axis horizontal, and the top place at rest at the highest position, the top would gradually start spinning as it moved down and around the pair of rings until it reach the bottom, then continued on up the other "side" - but not all the way. Some energy had been lost. Bill told us how he tried to increase the speed of the top to reach the point at which the magnetic force keeping it in contact with the rings would no longer supply sufficient centripetal force to keep the top moving in a circle, so it would then "fly off" -- but there were problems.

Next, Bill showed us another toy (**Lumberjack Toys,7651 Herrington
NE Belmont,
MI 49306)**
which used a tethered ball one could project up toward a
small basketball hoop, and try to make a "basket." Shows
transition of kinetic energy into gravitational potential
energy, as well as being fun. The toy is available at the following
location:

319 Central Avenue

Great Falls MT 59401

(406) 727-5557 [Bob Pechlin]

http://www.amazingtoys.net

Thanks, Bill!

**Carl Martikean (Wallace School, Gary, IN)**

showed us 2 sharp pencils, 4 sheets of Cartesian graph
paper, 1 tire pressure gauge, and asked - __How can we weigh
a car using this stuff?__

Answer - drive the car with each
one of the four tires standing on a sheet of the graph
paper. Trace the footprint of the tire on the each paper.
Use the gauge to measure the pressure in each tire. With
the graph papers on the table, measure the areas of the
footprints. The force on each of those footprints must
equal the pressure in the tire multiplied by the area of
the footprint. One must use the absolute or total air
pressure in the tire, which is the pressure measured by
the gauge plus atomospheric pressure. For example, if the
pressure gauge reads **26 pounds/square inch**, then we must
add **14.7 pounds per square inch** to **26**, for an absolute
pressure of **40.7 pounds per square inch**. Multiply by the
area of the footprint (suppose it is **30 square inches**),
and we have about **1200 pounds**. If each of the 4 tires is
identical, then the total force being held up (the weight
of the car) is **4800 pounds**! Thanks, Carl!

At this point those in the SMART Program left to a meeting
and we who remained enjoyed
**Lee Slick (Morgan Park HS)**, who wrote down the
squares of numbers ending in **5**:

5^{2} |
= |
25 |

15^{2} |
= |
225 |

25^{2} |
= |
625 |

35^{2} |
= |
1225 |

45^{2} |
= |
2025 |

etc. |

With Lee's help, we saw a pattern: All the results end in
**25**. If we multiply the ten's digit by the next higher
digit, we get the number to place before the **25**. To square
**35**, for example, multiply the **3** by **4** to get
**12**, and we have **1225** as the result. More neat
ideas! Thanks, Lee!