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): **
10:30 on 9-23-09
** first line ruler markings, distance in actual cm between ends, how obtained: **
0,7.5
7.50
I put the 0 mark on the crease of the first rubber band and where the bottom crease hit on the ruler was my second market hit on the ruler so then I took 7.50-0 to get 7.50cm. I marked the rubber band with a marker. I believe I am within the .03 of my measurements.
** The basis for your uncertainty estimate: **
since I measured with a ruler I think it is a bunch of your uncertainty because it is hard to hold the ruler and measure a little rubber band. If you could measure it laying down it would be more accurate.
** 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
7.5
7.5
7.5
7.5
7.5
these are the measurement that coninside with the marking on the rubber band. the first number after the word End is the rubber band marked with 1 mark and the second number is rubber band 2 and so on.
** Distances between ends when supporting 2 dominoes **
7.6 ,7.6 ,7.6 ,7.6 ,7.6 ,7.6
These are the measurement of 2 dominos
** 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
7.6 ,7.6 ,7.6 ,7.6 ,7.6 ,7.6 .38 n
7.8 ,7.8, 7.8 ,7.8, 7.8, 7.8 .76 N
7.9 ,7.9 ,7.9 ,7.9 ,7.9 ,7.9 1.14 N
8.0 ,8.0 ,8.0 ,8.0 ,8.0 ,8.0 1.52 N
8.2 ,8.2 ,8.2 ,8.2 ,8.2 ,8.2 1.9 N
End
** Describe the graph of your first rubber band **
the graph is increasing at an increasing rate.
the 6 rubber bands are all stretching at the same rate which gives them the same lengths.
End
** The tension force in your first rubber band at length 9.8 cm: **
3.42 N
** The length of your first rubber band when tension is 1.4 N: **
7.97 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 ,.35 ,.74 ,1.18 ,1.44
My line of best fit follows pretty close to the actual weights pretty 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 actually went with the given lengths found.
** The typical error you estimate when predicting force for a given length from your graphs: **
I think I would be pretty close to the actual force because my graph was pretty close to the actual measurements. I believe I could be with in +-.05 since my measurements are close to the actual numbers.
** The typical error you estimate when predicting length for a given force from your graphs: **
I think I could come within .5cm since my graph showes that I am pretty close to the actual lengths when measured I come pretty close.
** **
2.5
** **
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).