In this lab experiment the overall purpose was to prove that energy exists in one way or another, and does not simply disappear. Thus proving the conservation of mechanical energy. Through a test gravitational potential energy using a cart, pulley, and mass hanger we determined the change in energy / change in distance was (1.35 x 10-2 +/- 0.0014 N/m). Our graph shows a plot of potential energy, kinetic energy, and total energy which contained a linear fit. The linear fit of total energy was shown to be almost zero which shows that nearly all potential energy was converted to kinetic energy. The tiny amount that was not converted is assumed to be exerted as a friction force. Our second experiment, using a spring and counterweight, tested spring potential energy and showed that ℇ was (1.47 +/- 0.007 J). This answer was obtained through a series of calculations shown in my lab notebook pages. We used formulas from the lab manual to calculate this answer. While the expected answer is zero, our answer is close. Again, this answer could’ve been affected by friction between the string and pulley as well as error in measuring the displacement of the spring when the counterweight was dropped. Overall, our experimental results support the theory of conservation of mechanical energy.
Our first experiment testing gravitational potential energy yielded an answer of (1.35 x 10-2 +/- 0.0014 N/m). This was a representation of change in energy / change in distance. The expected answer for this experiment is zero and while that was not our answer, we were close. This shows that nearly all potential energy was converted to kinetic. Something that could’ve caused error in our answer was the small friction force between the cart and the track. We tried to negate this force by attaching 9 paperclips to the string and we believe it worked pretty successfully. Since this extra weight was added solely to negate friction forces, we did not include the extra weight in any calculations. As for our second experiment testing spring potential energy, we found ℇ to be (1.47 +/- 0.007 J). The goal of this experiment was to text the conservation of energy. While our answer did not match the expected answer of 0 J, we were still in a range that proved our experiment to be pretty successful. The amount of energy that was not conserved could’ve stemmed from measurement error, and human error in measuring the displacement of the spring when the weight was dropped. A possible solution to fixing this error could be using video recording and slowing it down to measure the exact displacement of the spring. So, while not quite all energy was conserved according to our calculations , in both experiments the numbers we found were close to the expected answers of zero.
I would like to thank my lab partner Jacob Kauppi and my TA Bill for helping me in understanding and completing the lab.
Driscoll, D., General Physics I: Mechanics Lab Manual, CWRU Bookstore, Spring 2019.
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