phy201
Your 'energy conversion 1' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.
** #$&* Your optional message or comment: **
** #$&* How far and through what angle did the block displace on a single trial, with rubber band tension equal to the weight of two dominoes? **
2.56cm about 20 degrees
I measured from the pullback to the final position after being released. the dominoe rotated a bit about 20 dgrees from horizontal.
** #$&* 5 trials, distance in cm then rotation in degrees, with rubber band tension equal to the weight of two dominoes: **
3.2, 10 degrees
3.0 ,15 degrees
3.3, 20 degrees
3.4, 20 degrees
3.2, 8 degrees
I obtained theses number by stretching the rubber band back and releasing making a mark where the dominoe stack comes to rest.
** #$&* Rubber band lengths resulting in 5 cm, 10 cm and 15 cm slides: **
7.2, 10 degrees
7.6, 20 degrees
At rubber band length 7.2 the result was about 5.6cm distance, at rubber band length 7.6 the result was 9.1 distance not exceeding the 7.8cm of the rubber band since we do not want to go more than 30 percent of the original length of the rubber band.
** #$&* 5 trials, distance in cm then rotation in degrees, with rubber band tension equal to the weight of four dominoes: **
5.1, 0 degrees
6.2, 25 degrees
4.6, 30 degrees
5.5, 10 degrees
4.9, 20 degrees
These results are from a lengths of rubber band supporting 4 dominoes. I pulled back to that length and released for a total of five trials. From reported on each line the approximate turn in degrees made by the dominoe.
** #$&* 5 trials, distance in cm then rotation in degrees, with rubber band tension equal to the weight of six dominoes: **
10.2, 20 degrees
7.1, 20 degrees
6.4, 30 degrees
8.2, 20 degrees
5.3, 10 degrees
These are the results of rubber bands supporting 6 dominoes
** #$&* 5 trials, distance in cm then rotation in degrees, with rubber band tension equal to the weight of eight dominoes: **
none reported
** #$&* 5 trials, distance in cm then rotation in degrees, with rubber band tension equal to the weight of ten dominoes: **
none reported
** #$&* Rubber band length, the number of dominoes supported at this length, the mean and the standard deviation of the sliding distance in cm, and the energy associated with the stretch, for each set of 5 trials: **
3.22, .1483, 6.2cm, 2 dominoes, 1.22J
5.26, .6183, 6.4cm, 4 dominoes , 3.99J
7.04, 1.238, 6.7cm, 6 dominoes, 8.02J
I used the distance of stretch for 2, 4, 6 dominoes and the net force in newtons found to be .19N per dominoe, so for 4 dominoes fnet= 4 * .19= .76N then I multiplied that number by stretch distance dw=fnet * 'ds.
It looks like you multiplied the weight of the dominoes by the length of the rubber band. There are two problems with this. First, the weight of the dominoes is certainly relevant, but it's the force exerted by the rubber bands at the maximum length, i.e., it's the maximum force exerted on the interval, not the average force. Second, the rubber band exerts no force when its length is less than about 6 cm, so the interval over which the average force is exerted is less than 1 cm.
Note also the units: a Joules in a N * m, but you have calculated N * cm.
** #$&* Slope and vertical intercept of straight-line approximation to sliding distance vs. energy, units of slope and vertical intercept, description of the graph and closeness to line, any indication of curvature: **
.22, 6.2
Slope is points on the graph y/x, y is the distance x is the energy, the slope would be distance/energy.
The data points are clustered closely to the line and there is a slight curvature.
** #$&* Lengths of first and second rubber band for (first-band) tensions supporting 2, 4, 6, 8 and 10 dominoes: **
.22, 6.2
The slope is the y axis divided by the x axis so it is units of cm/J. Same for the vertical interscept.
My data points are clustered closely aboutt he line, and they seem to curve a bit.
It seems to have an upward concavity, increasing at an increasing rate.
** #$&* Mean sliding distance and std dev for each set of 5 trials, using 2 rubber bands in series: **
6.2cm, 6.1cm
6.4cm, 6.5cm
6.7cm, 6.7cm
none for 8
none for 10
** #$&* Slope and vertical intercept of straight-line approximation to sliding distance vs. energy, units of slope and vertical intercept, description of the graph and closeness to line, any indication of curvature: **
3.88, .8983
6.24, .5029
9.24, .9965
none for 8
none for 10
** 1-band sliding distance and 2-band sliding distance for each tension: **
3.22, 3.88
5.26, 6.24
7.04, 9.24
none for 8
none for 10
** #$&* Slope and vertical intercept of straight-line approximation to 2-band sliding distance vs. 1-band sliding distance, units of slope and vertical intercept, description of the graph and closeness to line, any indication of curvature: **
slope=1.78, 5
The slope and y intercept are distance 2 divided by distance 1 in units of cm.
The line seems to be a straight line
** #$&* Discussion of two hypotheses: 1. The sliding distance is directly proportional to the amount of energy required to stretch the rubber band. 2. If two rubber bands are used the sliding distance is determined by the total amount of energy required to stretch them. **
This hypothesis is supported. I believe this because the slopes were the same for both the one rubber band and the two rubber band stretches
** #$&* How long did it take you to complete this experiment? **
about 3 hours
** #$&* Optional additional comments and/or questions: **
Your data look OK, and much of your analysis is fine. However your calculations of energy are not correct.
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