By Joe B. and Shelley G.
February 2010
Purpose of Experiment
This experiment helps us to understand what factors, the length of the string, the mass of the bob, or the angle of release, affect how long each period or swing of the pendulum takes.
Hypothesis
Before we began the experiment, we hypothesized that changing every variable would affect the swing time of our pendulum.
Set-Up
Sample set-up of the apparatus.
Procedure
1. First, collect all the items necessary for the experiment (pendulum stand, string, bob, stopwatch, protractor).
2. Next, create tables to collect the data.
3. Then, decide on what the constant length of string and angle of release to use.
4. Next, set up the pendulum stand according to the decided constants.
5. Then, choose a bob and perform three trials while measuring how long it takes the bob to swing ten times and record results.
6. Next, with two other bobs of different masses, repeat step 5.
7. Then, using a constant mass and string length, try three different angles of release, still performing three trials and record the results.
8. Repeat step 7, using a constant mass and angle of release, and use three different string lengths.
Data
Analysis
After the conclusion of our trials we discovered that changing the length of the string is what changes the average period of the pendulum swing the most. Our first trial was changing the mass of the bob attached to the pendulum. This change in mass yielded very small differences in the average period. We believe this occurred because adding more or less mass onto the pendulum would not change the amount of force of gravity exerted on the apparatus. Next we changed angle of release. After our trials the results were similar to that of the first trial with the change in mass. The average periods were all relatively close. Therefore we were able to conclude that changing the angle measure does not affect the average period. We believe this because the angle measurements we chose were very close together, 10 degrees, 20 degrees and 30 degrees. Because these angle measurements were so close, the average periods would be close as well. In our final trial we changed the length of the string. After we had recorded the results, we realized that the average periods were quite different. Therefore the length of the string is what truly affected the average period the most. We believe this happened because a shorter string would yield a much quicker time than a longer string. This is because a short string travels less distance and therefore it takes less time for one period whereas a long string travels a longer distance and therefore takes more time for one period.After collecting and analyzing our data we were able to conclude that the length of the string greatly affects how long each period takes.
Sources of Experimental Error
Our major experimental errors were random errors made because some of the measurements required for this project are impossible to make entirely accurate by a human. One of our random errors was not being able to start and stop the stopwatch at the exact moment the pendulum started and ended its swinging. This also affects the accuracy of the angle of release because if we were not able to start the stopwatch at the same time we dropped the pendulum from the measured angle, we started the timer at smaller angle than what we measured thus skewing our final results. Not only do our timing difficulties cause an inaccurate angle of release, but our initial measurement of the angle does too; it is nearly impossible to measure and start the pendulum from, for example, exactly 20 degrees and then repeat that exact same starting point for the other repetitions of the trial.
Summary
The purpose of this lab was to determine which variable, mass, length or angle measurement affected the time of the pendulum swing the most. Our original hypothesis was that each variable would change the time of the pendulum swing. After numerous trials, we were able to come to a distinct conclusion. We discovered that changing the length of the string would affect the time of the pendulum swing most drastically. We were able to come to this conclusion because we tried swinging the pendulum with different masses, different lengths and different measurements of the angle. After each separate trial we looked at the average period. These results yielded a distinct conclusion. When we changed the length of the string the difference in average period was the greatest and therefore the angle measurement affected the time of the pendulum swing the most. Overall, we felt as though lab was a success. Although we may have encountered some sources of experimental error, we still feel as though the lab was successful. Even though our hypothesis were not correct, we were able to determine the true answer to the original question and because of this we felt our lab was successful.
You guys did a great job! This website possesses an enticing title, and you put it together in an organized and attractive way. Although you structured the website well, you could have used a greater variety of colors. Some of your sentences, especially in the sources of experimental error portion, were long and unclear. But there was plenty of great detailed that supported your analysis, and it explained the results of your experiment well. Overall, you guys made a great website that gives a lot of sensitive insight into the factors that affect the time of a pendulum.
Great job, guys! I really like the appearance and format of the site (especially of the text), although the dark blue background makes the graphs a little difficult to read. I think you guys did a great job on your analysis paragraph especially-- very well written.
Your website is set up accordingly, and the creative title is a very nice touch. If your graphs/tables and picture had been centered it would make your website perfect. I really enjoyed reading this lab, the paragraphs may be lengthy but are worth reading. Great job!
Willy, may I ask what pleasure or advantage the title was offering you? Because it didn't offer me anything and I feel left out! Otherwise I'm confused as to why Shelley and Joe's title was 'enticing'.
Your site is well designed and clearly presented, however I feel that your analysis could have been broken up into sections addressing each variable. This also would have aided in the aesthetics. However the graphs are hard to read because of their coloring and the dark background. Also your hypothesis doesn't address the idea that one of the factors would affect the period the most. However, your analysis is concise and clear and the site's organization is great!
Great Job Shelley and Joe! I can see that you put a lot of time and effort into this lab. Your webpage looks organized and neat. I love the title too. The only thing I found that could possibly be changed are the decimal places in the table. But don't worry, I can see that you were persistent on being thorough.
Sebastian
Overall, the website flows very well and is easy to read. The tables and graphs blend well with the website design. I found that he summary is a little long and just a touch repetitive, though. However your analysis and sources of experimental error have amazing depth and are well presented. Good job!
Nice job guys! The information flows in a logical way and the data seems accurate. I don't love the with white contrasting against the blue though, i is a little tough to read and i believe we were supposed to exclude "human error" in our error analysis but I could be mistaken. Overall, this a fantastic website. Nice work.
Nice website Joe and Shelby! Everything is neat and well presented. I think the graphs should have a different color because it is a little hard to read. Also seems like your hypothesis is a little mundane. Other than that I feel like this page is A+ quality.