HW#9: Energy Conversion and Conservation of Energy Name: Group Galileo s Pendulum Experiment 1: Play the video Galileo Pendulum 1. Watch the entire video. You could check out the Pendulum lab simulation on the PhET website (PhET.colorado.edu) to help answer the questions. 1. The first video contains a 2 part experiment. Describe what changed from part 1 to part 2. 2. Compare the initial and final height of the pendulum in the first part of the experiment. What did you observe? 3. Compare the initial and final height of the pendulum in the second part of the experiment. What did you observe? 4. What is the purpose of the long horizontal rod in the experimental setup? Not the one that was inserted later, but the one that stayed there throughout the experiment. 5. Point A represent the starting position of the pendulum; point B represents the lowest point of the pendulum during its swing and point C represents the highest point the pendulum reaches on the other side during the first part of the experiment. Describe the energy conversion that is taking placing during the pendulum s swing from point A to point C. 1
6. Use the idea of energy conversion and conservation of energy to explain the observations you made in Question 2 & 3. Be thorough but keep it as short as you can. Use proper terms. 7. Use point D to represent the mid way point between point A and Point B. Draw three side by side pie charts showing the amount of total energy, kinetic energy and potential energy at each position. 8. Use point D to represent the mid way point between point A and Point B. Draw three side by side bar graphs showing the amount of total energy, kinetic energy and potential energy at each position. 2
Name: Group Galileo s Pendulum Experiment 2: Play the video Galileo Pendulum 2. It is a more thorough investigation of the same concept/idea explored in the first video with some twists. Luis (the guy in the video) releases the pendulum from a same height but with a rod in the way of the pendulum at different heights. There are 6 segments of the experiment, with the rod at different height in each segment. Watch one segment at a time. Stop at the time points as instructed. Before watching the results in each segment, predict the pendulum s position when it reaches the highest point on the other side. Then watch the result and draw a diagram to illustrate what you see. Doing so will make it easier to keep track of what happens and figure out why it happens. 1. Watch the video from 00:00:00 to 00:00:18. Pause the video and predict how high the pendulum will rise when it reaches the maximum height on the other side: higher than, at the same height as or lower than the height it was released at. 2. Watch from 00:00:18 00:00:25. Draw a diagram showing the starting position of the pendulum and the point when it reaches the highest point on the other side of the swing. For both positions, include the string and the pendulum in your diagram. Try to reproduce accurately what you observed in the video. Points will be assigned to the accuracy of your depiction of the observation. 3
3. Watch the next (2 nd ) segment from 00:00:25 00:00:35. Pause the video and predict how high the pendulum will rise this time: higher than, at the same height as or lower than the height it was released at. 4. Watch from 00:00:35 00:00:41. How high did it rise? Draw a diagram showing the starting position of the pendulum and the point when it reaches the highest point on the other side of the swing. Again, make sure to include both the string and the pendulum for each position. Show the approximate position of the rod using a round sphere. Try to reproduce what you observed in the video accurately. 5. Now watch the 3 rd segment (stop at 00:00:51). Predict how high the pendulum will rise. 6. Watch the experiment (stop at 00:00:56). Draw a diagram showing the two positions of the pendulum on both sides. 4
7. Now watch the 4 th segment (stop at 00:01:15). How is the placement of the rod different from the first three placements? Predict what will happen to the pendulum this time. 8. Watch the experiment (stop at 00:01:20). Draw a diagram showing what happened this time. Depict as accurately as you can the position of the pendulum and any difference in its motion. 9. Now watch the placement of the rod at the 5 th position (stop at 00:01:28). Make your prediction. 10. Watch the experiment (stop at 00:01:33). Draw a diagram showing what happened. 5
11. Watch the placement of the rod at the 6 th position (stop at 00:01:43). Make your prediction. 12. Watch the experiment. Do your best to illustrate what happened this time. You can describe what happens to supplement your drawing. 13. Identify at least two key points (with different rod placements) during this experiment when the behavior of the pendulum/string changed noticeably from the previous placements. Describe the new behavior at each key point. 14. Try to explain what causes the behavior of the pendulum to change at each key point. This question requires some brain power. Get together and discuss with your group members if you can. This question will be mostly graded on effort. Hint: think conservation of energy and what type(s) and how much energy the pendulum has at the highest point on the other side of the swing. 6