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: **
1,4.4
3.44cm
I measured with a reduced copy of a ruler the very end of the rubberband hanging from the first paper clip to the very end attached to the second paperclip. The rubberband is marde with a 1 in the center to verify this is the first rubber band. I believe my measu. is within the .05cm estimate.
** The basis for your uncertainty estimate: **
The rubberband appeared to be right on the 4.4 mark however there is some room for error since the paperclip was influencing my measurment by creating a gap where my ruler laid and becuase i was holding and measuring at the same time my ruler may have moved a little.
** Positions of the ends of each rubber band, actual lengths of each when the chain supports 1 domino: **
1,4.45
1,4.42
1,4.42
1,4.53
1,4.51
End
3.45,3.42,3.42,3.53,3.51
2,3,4,5,6
they were all within .05cm
** Distances between ends when supporting 2 dominoes **
3.51,3.52,3.56,3.60,3.70,3.68
This measurment was from the result of 2 donimos in the bag.
** Lengths when supporting 4, 6, ... dominoes: **
3.60,3.63,3.70,3.71,3.84,3.9
4
3.72,3.70,3.72,3.72,3.95,3.9
6
3.81,3.81,3.83,3.83,4.10,4.0
8
3.90,3.90,3.91,3.91,4.3,4.22
10
End
** Your table of force in Newtons vs. length in cm for all rubber bands **
3.45,3.42,3.42,3.53,3.51,.646,.646.650,.670,.667
3.51,3.52,3.56,3.60,3.70,3.68,.655,.669,.684,.703,.697
3.60,3.63,3.70,3.71,3.84,3.9,.684,.690,.703,.704,.730,.741
3.72,3.70,3.72,3.72,3.95,3.9,.707,.703,.709,.709,.750,.741
3.81,3.81,3.83,3.83,4.10,4.0,.723,.723,.728,.728,.779,.760
3.90,3.90,3.91,3.91,4.3,4.22,.741,.741,.743,.743,.817,.802
End
The meaning of first five number in each line is clear.
However there are five more numbers in each line. For example in the first line you have the numbers
.646,.646.650,.670,.667.
It isn't clear how you got these numbers or what they mean. Note, however, that the force required to support 10 dominoes is 5 times the force required to support 2 dominoes. Your numbers don't indicate this.
The force in Newtons is equal to the weight of the dominoes.
Using your reported measurements:
3.60,3.63,3.70,3.71,3.84,3.9
4
3.72,3.70,3.72,3.72,3.95,3.9
6
3.81,3.81,3.83,3.83,4.10,4.0
8
3.90,3.90,3.91,3.91,4.3,4.22
10
and assuming that each domino has a mass of 20 grams, the forces would be
3.60,3.63,3.70,3.71,3.84,3.9, .8 Newtons
3.72,3.70,3.72,3.72,3.95,1.2 Newtons
etc.
The first six comumns will show the length of the 6 rubber bands in cm. The second six columns will show the Force exerted on each individual rubber band in N
** Describe the graph of your first rubber band **
first rubber band- had a slowly increasing curve not very steep
second- similar to the first matching in many points.
third-here the curve increases more quickly than the first two this is the first noticable change.
fourth- is similar to the third curve and has a steeper slope than the fisrt 2 rubber bands but has many matching points similar to the third
fifth- there is another noticable jump in the curve it increases quicker than any other so far and is the steepest of the others. It is increasing 2x as fast as the first rubberband.
sixth- looks like the fifth graph however the fifth graph is just a tad steeper than the sixth.
End
It appears the fifth rubber band exerted most of the tension and had the greatest stretch overall therefore exerted the most force.
** The tension force in your first rubber band at length 9.8 cm: **
1.80N
this is with one domino
** The length of your first rubber band when tension is 1.4 N: **
3.7cm
with 4 dominos
** 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: **
** 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: **
na, .50,3.75,4.2
na,na, .25,na
I do not have enough information for some of these values because my graph and results did not reach as low as .19N and as high as 1.14N. I may have done someting wrong in my calculations if I am missing so many answers?
Your forces don't appear to be correct, per my previous note.
** The typical error you estimate when predicting force for a given length from your graphs: **
In my table because as stated before I had to estimate the direction the curve would take based on a small sample of my data. I do not have much faith in my graph.
+- .20 because my graphs were not very accurate I did a larger scale graph therefore leaving more room for uncertainity. My points did not seem to touch the line and by the distance of the points from the line I estimated my uncertainty.
** The typical error you estimate when predicting length for a given force from your graphs: **
+-.10 because my length was easy to determine. I was more accurate plotting my x axis.
** **
2hrs
** **
I was confused about plotting some of the graphs because my Force did not seem accurate. I was also confused which graphs I was supposed to refer to for certain questions. I will be happy to go back over this lab if necessary but I do understand the results.
As you suspect, there's something amiss with your forces. See my notes and revise (or ask questions) as appropriate.
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