OBJECT:

To make a Rubber band Scale.

MATERIALS:

Goggles for safety, BE SURE TO ALWAYS WEAR YOUR GOGGLES, WHEN WORKING WITH OBJECTS, THAT MAY BE ACCIDENTALLY PROJECTED !   ( always expect the unexpected ), Metric ruler, a straw, with a metric strip glued to it, ( see section on how to make metric strips ! ) several small rubber bands, several medium large rubber bands, which will serve as our main rubber band, several paper clips, and heavy duty string.

PROCEDURE:

1. Try to construct the set up in the above diagram, after reading all the directions first.

Remaining true to Hooke's law, we are using a rubber band in place of a spring! Having made several spring scales, using spring form a window shade, and housing of a split 1/2 inch PVC pipe. I found that it takes to much work, and decided to go for the very inexpensive rubber band instead. Since the spring scale, or should I say the rubber band and ruler, are at best not as accurate as the SBB we can use it, in finding out the relative weight of objects. I recently saw a Fish Spring Scale with a built in tape ruler, that you may purchase at your local store. I have no idea as to how much it sells for, but if you can afford it, it may not be a bad idea.

2. Notice that the top paper clip, has been bent, so that it can accommodate the top hole in the ruler. After attaching the main rubber band, try to make the paper clip flush to the ruler, secure the top paper clip, with some small rubber bands, if that is not sufficient, use some bell wire or masking tape, or what ever you may have handy, so that paper clip is secure in that position.

3. Notice, that it uses a main rubber band, you will have to judge the size of this rubber band, if one rubber band is to weak, you may have to double this rubber band.

4. Obtain a metric strip ( see section on how to make metric strips ! ) My metric strips are about 1 cm wide, if I had to I could make them narrower. You may want to use a commercial restaurant's straw, because of their width, the next time when you drink your soft drink, remember to bring the straw home. Attach your metric strip to the side of the straw, you may want to use a piece of clear tape, at the top and bottom of the straw, or you may want to use " Elmer's glue stick ", then carefully, with a pair of scissors, dissect it vertically. You now can slide the dissected straw on to the side of the metric ruler. ( See diagram above ) Then use the small rubber bands to hold the straw. When you have taken the slack out of the main rubber band, you have to adjust the straw with the metric strip, so that the paper clip pointer is pointing to zero !

5. You are now ready to calibrate the rubber band that you have decided to use. Use the same procedure as you used in the lab " Gravity ".

6. ALTERNATIVE METHOD, NOT SHOWN IN THE DRAWING ! You may want to purchase a six inch ruler ( or just use another 12 inch ruler ), with the corresponding centimeters on it. And use that small rubber band and ANOTHER small rubber band to secure the small ruler to the large ruler. Now you can move your small ruler so that the pointer is set to ZERO on the small ruler, and proceed to calibrate your rubber band.

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