Lab 10 (energy of a tossed ball) PDF

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Tenth lab report in Sup's course...

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Individual Report: Energy of a Tossed Ball Analysis of Results: The results were expected in that our calculated total energy was very close at each of the three points we chose to analyze. After release (t= 0.9324 s) total energy was 4.317 J, at the top of the path (t= 1.1655) it was 4.308 J, and before catch (t= 1.3986) it was 4.268 J. The potential and kinetic energies were fairly different, but the total energy was almost the exact same. The error between the after the catch and before catch times to top of path was 0.009 J and 0.040 J respectively. The experiment was valid because we accomplished the objective and determined potential and kinetic energies of a ball and used them to determine the total energy at different times throughout the balls movement and saw that total energy was conserved. There were not any major in the trends besides that which the experiment showed that as potential energy of the ball rises the kinetic energy lowers and that as it lowers, kinetic energy rises. When kinetic energy is at its maximum the potential energy is at its minimum and vice versa. The practical implications of the results are that it has become easier to understand/see how the potential and kinetic energy of an object as it moves off and moves toward the ground change and how the total energy remains constant. Actually observing this phenomenon of energy and seeing how it actually is conserved in real life and not just in equations or simulations helps me to understand the way it works with respect to objects in the world around me. Improvement: The major sources of error in this experiment came from the uncertainty/random error that the technology and tools used to calculate the values in this experiment since there was not a lot of human manipulation that could have influenced the values we measured. With this in mind, it would be very hard to improve upon this error and do anything to decrease the error with what we have available in lab. Performing more trials would help reduce random error in the experiment, though, and would have allowed use more data points to get more accurate results overall. There was some human error though because we had to toss the ball in the air and it was hard to get the trajectory to be exactly up and down without some curvature so our graphs were not as smooth as possible. We could have improved upon on this by taking more time and redoing the sample until we got a very smooth graph, although for the sake of time we stopped and used one that was just pretty good. With a more accurate graph we would have pulled more accurate data points from the graph and calculated our kinetic energy with a more accurate velocity and thus kinetic energy by the equation: KE= (1/2)mv2. If the more accurate velocity would have been a little lower for the after release value and a little higher for the before catch value the error would have been reduced because the calculated KE would have been lower for after release since v would be smaller and a little higher for before catch since v would be bigger and both would have closer to the value to top of path total energy, after their potential energies were summed with their kinetic energies. Individual Questions: To answer the preliminary questions, in regards to the first when the ball is at the top of the path at rest it has potential energy. For the second while it is in motion and nearly at the

bottom it has basically all kinetic energy, but just a little potential if it is still off the ground. We did not have to 3-5, but for question 6 the change in the ball’s potential energy is related to the change in kinetic energy proportionally by way of a negative relationship where as one shrinks the other increases. For the analysis questions, for question two this experiment shows very well how conservation of energy works because even though the potential and kinetic energy values are different for each time point along the ball’s path, the total energy is always shown to be constant (although there is some variance from random error). For 6, the shape of the kinetic energy versus time graph can be explained by the fact that at the beginning of the toss it is high since the ball is thrown into the air and the speed is highest as it is thrown, but then slows down by the negative acceleration on it due to gravity so the kinetic energy decreases to zero as the ball is at a rest at its maximum height and not moving, then peaks again as it increases speed moving down toward the ground again where it becomes zero, like at the start, because the ball is caught and stops moving. For 7, the potential energy versus time graph shape can be explained by essentially the reverse of question 6. In the beginning when the ball is near the ground it has low potential energy because it depends on height and it is moving quickly up though so it gains energy until it is at its peak height and at rest and all of its energy is potential, but then decreases as the height decreases as it falls toward the ground again until it is at near zero when its caught near ground level. For 11, the total energy should remain constant, theoretically, though this does not occur because some of the energy is lost to other transfers, such as heat, interactions with the ground, or overcoming the drag of the air. For the extension questions, in regards to number one, if we used a very light ball instead of the one we did use the same trends would occur, but less total energy would be present and all values of potential and kinetic energy would be lower because the mass would be less and all the energies in this experiment increase with increasing mass. For the second, if we entered the wrong mass in this experiment each of our energies would be incorrect because, as stated for the previous question, the energies all are affected by mass....