Purpose: |
1) Use the law of conservation on energy to calculate K for a marble launcher.
2) Establish a mathematical relationship between compression of a spring and its potential energy. 3) Derive an equation for spring force vs. compression distance. |
The Tools for the job: |
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Method to Madness: |
This one is simple enough:
We used a large strip of paper that was about 3 meters high, with lines denoting each tenth of a meter as a backdrop to our vertical launching area. We pointed the "wrong end" of the launcher vertical, and started "shooting" marbles upward. We then recorded the height of the launches and looked at the films later in order to determine the height of each launch. The first three launches of each spring setting in our launcher were then recorded on an excel sheet, seen below. |
A snapshot of what happens:Here you can see a scientist preparing to test fire the launcher apparatus. The launcher was previously set in a vertical position, and the paper was accurately measured with the meter stick.
At this particular moment, this scientist in our group is setting our launcher (yes the same kind seen in the title photo) to the lowest setting, which is exactly .111 meters from the top of the barrel (each position tested was measured, as noted in the excel spreadsheet below). The scientist would call out the position and launch the marble. Variables:Independent:
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Conclusions: |
We were quite successful in all three endeavors:
1)Found the K of the marble by setting it equal to the potential energy in the spring (2mgh/x^2=k). 2) Found the relationship of compression and potential energy, which can be seen in the excel graph above (using line of best fit). 3) Derived an equation of spring force vs. compression distance (seen on excel sheet). |
Sources of error: |
Sadly, nobody is perfect, so there is going to be some error with any lab.
Our sources of error were: -Having to eyeball the height for each launch. -If the launcher's fingers got in the way (which did happen), we had to scratch data. -All groups shared data, so if one of us is wrong, we all are. -We did not account for air resistance. -----Also, -Each data point is incorrect by approximately 1/5 of a meter, which is the height of the top of the launcher, where the marble sat at rest. Since the error is perfectly consistent however, it has no effect on final conclusions. |
Photo of a scientist credit to: http://mysite.cherokee.k12.ga.us/personal/kimberly_geddes/site/pages/AP%20Physics%20C.aspx
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