Black Box Experiment
or, how to see with your eyes what you can't see with your eyes.
Materials :
Good Graphing software that can make 3D graphs, like Microsoft Excel, or AXUM
Milk crate (cubic, plastic)
Black cloth (should block light but allow a needle through, then close up without leaving a hole to look through)
Probe (a thin knitting needle, or a stiff thin wire, somewhat sharpened so it penetrates the cloth)
Board (to set the milk crate on)
Bungee cord (to strap the crate to the board. I drilled two holes in my board to put the bungee hooks through)
Thing (this gets attached roughly in the middle of the board with 2 screws, so it doesn't rotate. It could be anything that fits comfortably inside the milk crate: a couple pieces of scrap wood, a bust of Beethoven, a telephone.....)
Procedure :
Teacher instructions : Screw the thing to the middle of the board. Turn the milk crate upside down, and drape the black cloth over the crate. If you have enough cloth, you may want to double it. The key is to get enough cloth so that students can't see through it, both before and after they probe through it. Put the crate over the thing on the board, and tuck in the cloth so it's pretty snug. Bungy the crate to the board. Check : crate tight on board ? Not too much loose cloth inside the crate ? Probe easily penetrates cloth and reaches thing ? Cloth closes behind probe when it's removed ?
Look at the samples to get a better idea of what you can do :
3 views of a 3d graph generated from the sample data :
| View 1 | View 2 | View 3 |
Student Instructions :
a) On graph paper, make a 2 to 1 scale drawing of one side of the milk crate. This means if the crate measures 20 cm high, your drawing should be 10 cm high.
b) Choose a side of the crate to begin probing. Label it "Side A" with a piece of tape. Label your drawing "Side A" also.
c) Push your probe through a hole in the crate. Note exactly where (horizontal & vertical distances) the probe is going into the crate. On your drawing, locate the same spot, and write the depth in cm that the probe entered before it hit the thing. If it hit nothing, write the depth as the width of the crate.
d) Caution : Make sure the probe is straight !!! If it's not straight, you'll get bad information.
e) Move across the face of the milk crate methodically gathering depth information and meticulously recording the information on your drawing. You should at least get information from every hole in the crate, and you should be able to get 2 or 3 or 4 depth measurements from each crate hole.
f) Finished ? Get on a computer. Open up Microsoft Excel (or some other graphing program your teacher recommends.) The directions to be follwoed should be supplemented by your teacher so they apply to the software you are using.
g) Starting at the top, enter your depth numbers in the spreadsheet cell that corresponds most closely to the graph paper square where each one is written down. Hopefully, by the time you're done putting your numbers in the spreadsheet, you have put numbers into about the first 25 columns, and down the first 25 rows.
h) If you didn't make a measurement, leave that cell blank, or go make a measurement that can fit there.
i) Then, save your data !
j) Then, graph your data using some kind of 3D graph. If you can, rotate the graph.
Can you tell what the THING is ? If not, try looking at some of the other student-made graphs.