rubber band calibration

phy 121

Your 'rubber band calibration' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.

** #$&* Your initial comment (if any): **

** #$&* first line ruler markings, distance in actual cm between ends, how obtained: **

10, 21.72

11.72cm

I got these numbers by using the ruler ruler that is singly spaced (the next smallest to the full sized one) and measuring from one end of hte rubber band to the other. I wrote in marker 1-6 on the corresponding rubber band. I believe that these measurements are accurate +-.04cm.

** #$&* The basis for your uncertainty estimate: **

It was hard to figure out how to measure the first one precisely. Deciphering where you were supposed to put the ruler and and what end to stop measuring was a little tricky. I also had to make sure that I was not stretching the rubberbands myself while measuring.

** #$&* Positions of the ends of each rubber band, actual lengths of each when the chain supports 1 domino: **

10, 21.72

10, 21.73

10, 21.24

10, 21.52

10, 22.12

10, 21.83

** #$&* Distances between ends when supporting 2 dominoes **

11.88, 11.92, 11.72, 11.73, 12.63, 11.92

these results were from the weight of 2 dominoes.

** #$&* Lengths when supporting 4, 6, ... dominoes: **

12.11, 12.62, 12.27, 12.35, 12.95, 12.42

12.66, 12.84, 12.60, 12.53, 13.26, 12.82

13.00, 13.55, 13.21, 13.15, 13.74, 13.62

** #$&* Your table of force in Newtons vs. length in cm for all rubber bands **

11.72, 11.73, 11.24, 11.52, 12.12, 11.83 .19

11.88, 11.92, 11.72, 11.73, 12.63, 11.92 .38

12.11, 12.62, 12.27, 12.35, 12.95, 12.42 .76

12.66, 12.84, 12.60, 12.53, 13.26, 12.82 1.14

13.00, 13.55, 13.21, 13.15, 13.74, 13.62 1.52

End

Each line represents the length of the rubber band depending on how many dominoes were in the bag. The first line is for 1 domino, the 2nd line is for 2 dominoes, the 3rd line is for 4 dominoes, the 4th line is for 6 dominoes, and the 5th line is for 8 dominioes. The last number in each column is supposed to indicate the number indicating newtons. However, I do not understand what I am really supposed to put for this last number. To get my numbers for the last number in each line I just kept on adding .19.

If you were supporting 2, 4, 6, 8 and 10 dominoes respectively, then the forces would be the weights of 2, 4, ... dominoes. Each domino has a weight of about .19 N. It looks like you have the correct weights for 1, 2, 4, 6 and 8 dominoes.

** #$&* Describe the graph of your first rubber band **

My first graph is increasing at a decreasing rate. All of my graphs for rubber bands 2 through 6 also seem to be increasing at a decreasing rate.

End

** #$&* The tension force in your first rubber band at length 9.8 cm: **

1.9 newtons

** #$&* The length of your first rubber band when tension is 1.4 N: **

9.4cm

9.3cm

** #$&* The forces at your observed lengths the 1st rubber band, as given by the curve, and the deviations of those curve-predicted lengths from the observed lengths: **

.39, .60, .79, 1.14, 1.54

If each domino equals.19 newtons than I would say that the difference between the results are pretty close. The first two have a greater difference than the others. The first number differs by .19, the second differs by .38, the third differs by .03, the fourth differs by .00 and the fifth differs by .02

** #$&* The lengths predicted for forces .19 N, .38 N, .76 N, 1.14 N, etc. by the curve for your first rubber band; the deviations of your actual observations from these predictions: **

11.72, 11.88, 12.10, 12.62, 13.00

** #$&* The typical error you estimate when predicting force for a given length from your graphs: **

I have more faith from the values in my table because I think that the distances on my graph might be a little skewed. I would say the uncertainty would be around +-.10 N and this comes from how far off some of my results were.

** #$&* The typical error you estimate when predicting length for a given force from your graphs: **

+-.05cm. My evidence for this comes from actually measuring and graphing these points. I tried to be as accurate as possible but either in measuring or graphing it is likely that there was a little bit of error.

2 1/2 hrs