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course Phy 121
energy conversion 1#$&*
Phy 121
Your 'energy conversion 1' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.
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energy conversion 1
#$&*
Phy 121
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.
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You will need something to which to attach the last hook:
• Now place on the tabletop some object, heavy enough and of appropriate shape, so that the last hook can in one way or another be fixed to that object, and the object is heavy enough to remain in place if the rubber band is stretched within its limits. That is, the object should be able so remain stationary if a few Newtons of force is applied. Any rigid object weighing, or being weighted by, about 5-10 pounds ought to be sufficient.
• Your goal is to end up with a moderately massive object, to which the last hook is tied or attached, with the rubber band extending from the hook to another hook, a thread from that hook to the block (with a shorter thread trailing from the other end of the block)
• With a slight tension in the system the block should be a few centimeters from the 'far' edge of the paper which is furthest from the massive object.
• If the block is pulled back a little ways (not so much that the rubber band exceeds its maximum tolerated length) the rubber band will stretch but the last hook will remain in place, and if the block is then released the rubber band will snap back and pull the block across the tabletop until the rubber band goes slack and the block then coasts to rest.
• The figure below shows the block resting on the paper, with the thread running from a hook to the rubber band at the far end, which is in turn hooked to the base of a flatscreen monitor.
At the far end the rubber band is ready to be stretched between two hooks. A measuring device is shown next to the rubber band; to get accurate measurements of rubber band length it is recommended that a piece of paper be placed beneath the rubber band, and two points carefully marked on the paper to indicate the positions of the ends. The separation of the points can later be measured. Alternatively the two points can be marked in advance at the desired separation and the system stretched accordingly.
Consult your previous results and determine the rubber band length required to support the weight of two dominoes. Pulling by the shorter piece of thread (the 'tail' of thread), pull the block back until the rubber band reaches this length, and on the paper mark the position of the center of the block (there might well be a mark at the center of the domino; if not, make one, being sure it is within 1 millimeter of the center, and mark the paper according to this mark). Release the thread and see whether or not the block moves. If it does, mark the position where it comes to rest as follows:
• Make a mark on the paper where the center mark comes to rest by drawing a short line segment, perhaps 3 mm long, starting from the center mark and running perpendicular to the length of the block.
• Make another mark about twice the length of the first, along the edge of the block centered at the center mark.
• This will result in a mark that looks something like the following, with the longer line indicating the direction of the block and the two lines coming together at the center mark: __|__. In the first figure below the lowest two marks represent the positions of the center of the dominoes at initial point and at the pullback point. The mark next to the domino is the horizontal part of a mark that looks something like |- ; the vertical part of that mark is obscured by the blocks, and the mark it also tilted a bit to coincide with the slightly rotated orientation of the block. In the second figure most of the |- mark can be seen.
You will make a similar mark for the final position for each trial of the experiment, and from these marks you will later be able to tell where the center mark ended up for each trial, and the approximate orientation of the block at the end of each trial.
• Based on this first mark, how far, in cm, did the block travel after being released, and through approximately how many degrees did it rotate before coming to rest?
• If the block didn't move, your answers to both of these questions will be 0.
Answer in comma-delimited format in the first line below. Give a brief explanation of the meaning of your numbers starting in the second line.
Your answer (start in the next line):
10.16cm, 35
The three dominos sped across 10.16cm of the paper before coming to a complete stop. The degrees it rotated was 35.
#$&* _ 2 rb tension how far and thru what angle
Tape the paper to the tabletop, or otherwise ensure that it doesn't move during subsequent trials.
• Repeat the previous instruction until you have completed five trials with the rubber band at same length as before.
Report your results in the same format as before, in 5 lines. Starting in the sixth line give a brief description of the meaning of your numbers and how they were obtained:
Your answer (start in the next line):
2.30cm, 0
2.30cm, 0
2.30cm, 0
2.30cm, 0
2.30cm,0
This was with the rubber band stretched from dominos in previous lab.
These were the span in cm the dominos covered when released and the degrees. My last two times really varied from the first three.
#$&* _ trials on paper
Now, without making any marks, pull back a bit further and release.
• Make sure the length of the rubber band doesn't exceed its original length by more than 30%, with within that restriction what rubber band length will cause the block to slide a total of 5 cm, then 10 cm, then 15 cm.
• You don't need to measure anything with great precision, and you don't need to record more than one trial for each sliding distance, but for the trials you record:
• The block should rotate as little as possible, through no more than about 30 degrees of total rotation, and
• it should slide the whole distance, without skipping or bouncing along.
• You can adjust the position of the rubber band that holds the block together, the angle at which you hold the 'tail', etc., to eliminate skipping and bouncing, and keep rotation to a minimum.
Indicate in the first comma-delimited line the rubber band lengths that resulted in 5 cm, 10 cm and 15 cm slides. If some of these distances were not possible within the 30% restriction on the stretch of the rubber band, indicate this in the second line. Starting in the third line give a brief description of the meaning of these numbers.
Your answer (start in the next line):
8.89cm
10.16cm
10.795cm
Each number is the length of the rubber band being extended in cm.
#$&* _ rb lengths for 5, 10, 15 cm slides
Now record 5 trials, but this time with the rubber band tension equal to that observed (in the preceding experiment) when supporting 4 dominoes. Mark and report only trials in which the block rotated through less than 30 degrees, and in which the block remained in sliding contact with the paper throughout.
Report your distance and rotation in the same format as before, in 5 lines. Briefly describe what your results mean, starting in the sixth line:
Your answer (start in the next line):
5.08cm, 5
4.70cm, 0
5.08cm, 0
5.20cm, 0
4.70cm, 0
These are the results from an extended rubber band. It shows the span of dominos across the paper and the degrees they rotated.
#$&* _ 5 trials 4 domino length
Repeat with the rubber band tension equal to that observed when supporting 6 dominoes and report in the same format below, with a brief description starting in the sixth line:
Your answer (start in the next line):
17.78cm, 50
17.78cm, 95
18cm, 50
15.24cm, 180
18.25cm, 60
With the rubber band stretched to accommodate four rubber bands in a bag, these are the measurements and degree it rotated.
#$&* _ 5 trials for 6 domino length
Repeat with the rubber band tension equal to that observed when supporting 8 dominoes and report in the same format below, including a brief description starting in the sixth line:
Your answer (start in the next line):
33.02cm, 180
41.91cm, 360
33.02cm, 100
33.56cm, 100
30.48cm, 180
These are the measurements for the stretch of a rubber band with eight dominos in the bag from a previous lab.
#$&* _ 5 trials for 8 domino length
Repeat with the rubber band tension equal to that observed when supporting 10 dominoes and report in the same format below, including your brief description as before:
Your answer (start in the next line):
48.26cm, 360
48.26cm, 360
41.91cm, 270
50.8cm, 360
45.72cm, 180
These numbers seemed to vary every time I did it.
#$&* _ 5 trials for 10 domino length
In the preceding experiment you calculated the energy associated with each of the stretches used in this experiment.
The question we wish to answer here is how that energy is related to the resulting sliding distance.
• For each set of 5 trials, find the mean and standard deviation of the 5 distances. You may use the data analysis program or any other means you might prefer.
• In the space below, report in five comma-delimited lines, one for each set of trials, the length of the rubber band, 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.
• You might choose to report energy here in Joules, in ergs, in Newton * cm or in Newton * mm. Any of these choices is acceptable.
• Starting in the sixth line specify the units of your reported energy and a brief description of how your results were obtained. Include your detailed calculations and specific explanation for the third interval. Be sure to give a good description of how you obtained the energy associated with each stretch:
Your answer (start in the next line):
&&&2.75in, 2 dominos, 2.3, 0
3in, 4 dominos, 4.952, .24,
3.50 in, 6 dominos, 17.40, 1.23
3.75in, 8 dominos, 34.398, 4.378
4.25 in, 10 dominos, 46.99, 3.36
The means are after the second comma and standard deviations follow.
###Energy is force*displacement/time.
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The energy does work, and the work is force * displacement, not force * displacement / time.
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2*.94=1.88J
4*1.15=4.6J
6*1.40=8.4J
8*1.78=14.24J
10*1.99=19.9J
Yes, 1N*m gives you Joules###
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Work is force * displacement.
Energy is equivalent to work so cannot be calculated as force / time or as force * displacement / time.
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2/.94=2.12J
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2 lacks units, as does .94; do the units of 2, when divided by the units of .94, give you Joules?
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4/1.15=3.48J
6/1.40=4.3J
8/1.78=4.50J
10/1.99=5.02J&&&
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It isn't clear that you've reported the energies associated with the stretch, and you haven't explained how you did so.
Which 'above numbers' have you reported the means? The numbers shown here don't appear to be related to the quantities you reported above.
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#$&* _ for each set of trials length, # dom, mean, std of sliding dist, energy _ describe how results obtained esp energy calculations
Sketch a graph of sliding distance vs. energy, as reported in the preceding space .
• Fit the best possible straight line to your graph, and give in the first comma-delimited line the slope and vertical intercept of your line.
• In the second line specify the units of the slope and the vertical intercept.
• Starting in the third line describe how closely your data points cluster about the line, and whether the data points seem to indicate a straight-line relationship or whether they appear to indicate some sort of curvature.
• If curvature is indicated, describe whether the curvature appears to indicate upward concavity (for this increasing graph, increasing at an increasing rate) or downward concavity (for this increasing graph, increasing at a decreasing rate).
Your answer (start in the next line):
&&&.79in, -4J
In, J
My graph actually makes a great curvature. Almost all of my data points touch the line.
As energy increases so does sliding distance. My curve is increasing at an increasing rate. &&&
#$&* _ sliding dist vs. energy slope, vert intercept of st line, how close to line, describe curvature if any
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You haven't answered the above questions.
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Now repeat the entire procedure and analysis, but add a second rubber band to the system, in series with the first.
• For each trial, stretch until the first rubber band is at the length corresponding to the specified number of dominoes, then measure the second rubber band and record this length with your results.
• When graphing mean sliding distance vs. energy, assume for now that the second rubber band contributes an amount of energy equal to that of the first. You will therefore use double the energy you did previously.
• When you have completed the entire procedure report your results in the space es below, as indicated:
Report in comma-delimited format the length of the first rubber band when supporting the specified number of dominoes, and the length you measured in this experiment for second band. You will have a pair of lengths corresponding to two dominoes, four dominoes, ..., ten dominoes. Report in 5 lines:
Your answer (start in the next line):
2- 5.08, 0, 6.35, 0, 6.35, 25, 6.35, 15, 12.7, 0
4- 22.86, 0, 17.78, 10, 20.32, 0, 22.86, 75, 22.86, 20
6- 35.56, 180, 25.4, 180, 22.86, 200, 38.1, 95, 27.94, 95
8- 43.18, 50, 58.42, 360, 58.42, 360, 38.1, 360, 38.1, 90
10- 45.72, 0, 45.72, 360, 66.04, 360, 58.42, 360, 50.8, 90
#$&* _ lengths of 1st and 2d rbs in series each of 5 trials
&&&I added this so you could see the measurement in cm, and the degree. For example, 35.56cm and 180 degrees. I did five trials for each line&&&
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Each line should have two lengths, one for the first and one for the second rubber band. You have reported much more than that, and it isn't clear what your numbers mean.
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Report for each set of 5 trials your mean sliding distance and the corresponding standard deviation; you did five sets of 5 trials so you will report five lines of data, with two numbers in each line:
Your answer (start in the next line):
2.75 in, 2 dominos , &&&7.366, 3.03
3in, 4 dominos, 21.336, 2.27
3.50in, 6 dominos, 29.972, 6.57
3.75in, 8 dominos, 47.244, 10.4109
4 in, 10 dominos, 53.34, 8.80&&&
#$&* _ sliding dist and std dev each tension
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The standard deviation will be significantly less than the mean for each set of observations.
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Give the information from your graph:
• Give in the first comma-delimited line the slope and vertical intercept of your line.
• In the second line specify the units of the slope and the vertical intercept.
• Starting in the third line describe how closely your data points cluster about the line, and whether the data points seem to indicate a straight-line relationship or whether they appear to indicate some sort of curvature.
• If curvature is indicated, describe whether the curvature appears to indicate upward concavity (for this increasing graph, increasing at an increasing rate) or downward concavity (for this increasing graph, increasing at a decreasing rate).
Your answer (start in the next line):
Slope and vertical intercept are both steep and increasing at an increasing rate. .
&&&79in, -4J&&&
Data points are clustered close to the line, but not all touch the line.
Increasing at an increasing rate.
#$&* _ slope, vert intercept, describe curvature
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You have not given the slope and the vertical intercept. Each is a single quantity, represented by a single number and its units.
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In the space below, report in the first line, in comma-delimited format, the sliding distance with 1 rubber band under 2-domino tension, then the sliding distance with 2 rubber bands under the same 2-domino tension.
Then in the subsequent lines report the same information for 4-, 6-, 8- and 10-domino tensions.
You will have five lines with two numbers in each line:
Your answer (start in the next line):
This was reported above.
#$&* _ 5 lines comparing 1 rb to 2 rb trials
Your preceding answers constitute a table of 2-rubber-band sliding distances vs. 1-rubber-band sliding distances.
Sketch a graph of this information, fit a straight line and determine its y-intercept, its slope, and other characteristics as specified:
• Give in the first comma-delimited line the slope and vertical intercept of your line.
• In the second line specify the units of the slope and the vertical intercept.
• Starting in the third line describe how closely your data points cluster about the line, and whether the data points seem to indicate a straight-line relationship or whether they appear to indicate some sort of curvature.
• If curvature is indicated, describe whether the curvature appears to indicate upward concavity (for this increasing graph, increasing at an increasing rate) or downward concavity (for this increasing graph, increasing at a decreasing rate).
Your answer (start in the next line):
The lines were drawn above.
#$&* _ graph 2 rb dist vs 1 rb dist _ slope and intercept _ describe any curvature
To what extent do you believe this experiment supports the following hypotheses:
The sliding distance is directly proportional to the amount of energy required to stretch the rubber band. If two rubber bands are used the sliding distance is determined by the total amount of energy required to stretch them.
Your answer (start in the next line):
This is true. The more energy exerted the more the dominos slide. If two rubber bands are in the system, the dominos are twice as fast.
#$&* _to what extend is hypothesis of sliding dist prop stretching energy supported _ to what extent for 2 rb
Your instructor is trying to gauge the typical time spent by students on these experiments. Please answer the following question as accurately as you can, understanding that your answer will be used only for the stated purpose and has no bearing on your grades:
• Approximately how long did it take you to complete this experiment?
Your answer (start in the next line):
:
3 hours
#$&*
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You appear to have good data, but not all the quantities you report appear to correspond to your data.
I've inserted a number of questions, each of which requires and answer or a clarification.
&#Please see my notes and submit a copy of this document with revisions, comments and/or questions, and mark your insertions with &&&& (please mark each insertion at the beginning and at the end).
Be sure to include the entire document, including my notes.
&#
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Check my notes and please submit a revision, using #### to indicate insertions.
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"
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This report is passable, but do see my note.
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