Day 8: Reproducibility

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Yesterday, the team studied the trend of gravitational acceleration values as masses of the balls differed. They also realized the importance of dropping the balls in parallel with the meter stick. So, today the team replicated the experiment keeping all the past discoveries in mind before moving onto the write-up stage. Like the other times, the team dropped the lead, steel, golf, wooden, and hollow plastic balls to check if they would be able to reproduce the same results as the previous trials. However, this time we took two trials for each ball to see the consistency.

Figure 1. Snapshot of PASCO Capstone file analyzing the video of the falling steel ball trial #3. To the right is the graph of Velocity vs Time for the falling ball.

As mentioned previously, the slope (m) of the best fit line of the Velocity vs Time graph will be our experimental acceleration value. As you see in the figure above, the gravitational acceleration for the falling steel ball is determined to be -9.83 m/s2. Recall the data collected for the steel ball from the trials on Day 3 gave us an acceleration of -9.79 m/s2. Similarly, on Day 7, the acceleration was found to be -9.8 m/s2. You can see that all three values are consistent and close to the accepted value of gravitational acceleration.

As mentioned earlier, today the team took two trials: trial #2 and #3 for each ball. Figure 1 above was the snapshot of trial #3. However, trial #2 gave us an unexpected acceleration:

Figure 2. Snapshot of trial #2.


Our initial guess for such an error in the acceleration value is that the camera wasn't leveled completely straight while taking the video. However, the team will look more into it tomorrow and possibly run a few more trials with the camera tilted at different angles to see any trends.


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