phy 201
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: **
0,7.5cm
7.50
I used my metric scale to measure the length of the rubber band, i put zero on the highest point and measured to the bottom of the rubber band. I think these measurementsare probable accurate to +-.05 cm, I think the measurement is probably somewhere between 7.45 and 7.55.
** The basis for your uncertainty estimate: **
Due to the fact that i am using a scale which is basically a comparative measurement, there will be a lot of uncertainties, if it was a direct measurement, there would not be as much uncertainty.
** Positions of the ends of each rubber band, actual lengths of each when the chain supports 1 domino: **
0,7.5
0,7.5
0,7.5
0,7.5
0,7.5
0,7.5
END
7.5 (Rubber band 1)
7.5 (Rubber band 2)
7.5 (3)
7.5 (4)
7.5 (5)
7.5 (6)
These are the actual measurements of each of the rubber bands.
I believe the uncertainty is around +-.05 cm.
** Distances between ends when supporting 2 dominoes **
7.6 , 7.6 , 7.6 , 7.6 , 7.6 , 7.6
These are the measurements of each individual rubber band with two dominos in the bag.
** Lengths when supporting 4, 6, ... dominoes: **
7.8 , 7.8 , 7.8 , 7.8 , 7.8 , 7.8
4
7.9 , 7.9 , 7.9 , 7.9 , 7.9 , 7.9
6
8.0 , 8.0, 8.0 , 8.0 , 8.0 , 8.0
8
8.2 , 8.2 , 8.2 , 8.2 , 8.2 , 8.2
10
END
** Your table of force in Newtons vs. length in cm for all rubber bands **
7.5 , 7.5 , 7.5 , 7.5 , 7.5 , 7.5 .19 N
1 (.19 N) [1 x .19 = .19]
7.8 , 7.8 , 7.8 , 7.8 , 7.8 , 7.8
4 (.76 N) [4 x .19=.76]
7.9 , 7.9 , 7.9 , 7.9 , 7.9 , 7.9
6 (1.14 N)
8.0 , 8.0, 8.0 , 8.0 , 8.0 , 8.0
8 (1.52 N)
8.2 , 8.2 , 8.2 , 8.2 , 8.2 , 8.2
10 (1.9 N)
END
** Describe the graph of your first rubber band **
Increasing at an increasing rate.
All six rubber bands are stretching at the same length because they are splitting the load throughout.
** The tension force in your first rubber band at length 9.8 cm: **
3.8 N
** The length of your first rubber band when tension is 1.4 N: **
7.95 cm
** 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: **
.19 , .36 , .73 , 1.17 , 1.42
My curve follows the actual weights very close.
** 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: **
7.5, 7.6 , 7.8 , 7.9 , 8.0 , 8.2
My curve follows the actual lengths pretty close(to be an estimate).
** The typical error you estimate when predicting force for a given length from your graphs: **
I would trust the actual recorded data because it is actual and not estimated, as in the curve on the graph. I would probably say that the uncertainty would be +-.01 N. I got this by taking the uncertainty of the length(+-.05) and multiplied it by .19 to get .0095 which i rounded up to .01.
** The typical error you estimate when predicting length for a given force from your graphs: **
I would guess the length would be +-.2cm because you would be estimating from a curve and not real data.
** **
2 hours
** **
Rubber bands are not manufactured to great precision, and it is highly unlikely that the lengths will all be the same under an identical load. Your results are probably not far from accurate, but I suspect your calibration, while probably reasonably close, is not particularly precise. This might affect the accuracy of subsequent experiments that use the rubber bands (however uncertainly on those experiments is fairly high anyway and this might not be a big factor).