Force and Motion

I chose to focus my guided inquiry on the question which pendulum will come to rest more quickly, a lighter pendulum or a heavier pendulum?  To conduct this inquiry, I used three washers with different diameters: 1/2”, 1”, and 1.5”.  Each washer also had different masses.  In addition to the washers, I used a string, the arm of a document camera, and a 13” ruler.  I tied the 1/2” washer to the string and tied the string at a length of 9 inches to the arm of the document camera.  Keeping the string pulled tight, I lifted the washer to a height of 13 inches and dropped the washer.  As soon as I dropped the washer, I started a timer to keep track of the time it took for the washer to come to rest.  I recorded the elapsed time in my notebook.  I repeated the procedure three times and averaged the time it took for the washer to come to rest.  I recorded the average time.  I did the same thing with the other two washers using the same string.  I discovered the 1/2” washer came to rest quicker than the other two washers, and the 1” washer came to rest quicker than the 1.5” washer.  The results were what I expected.  The results confirmed the concept that “the greater the mass the greater the inertia, or resistance to change in motion” (Tillery, Enger, & Ross, 2008, p. 41).  

I faced some challenges during my guided inquiry experience.  My biggest challenge was starting the timer at the same time I dropped the washer.  This proved to be more difficult than I expected.  I either hit the start button right before or right after I released the washer rather than simultaneously with the dropping of the washer.  Another challenge was ensuring I dropped the washers without adding more force or twisting the washer on the string.  I attempted to solve this problem by balancing the washer on the ruler and dropping the ruler to release the washer.  Using the ruler to drop the washer also caused challenges.  There were instances when either the hole in the center of the washer or the string caught on the ruler and disrupted the flow of the first swing.  When this happened, I had to stop the washer and start again.  Time became a challenge due to starting, stopping, and restarting the initial dropping of the washer. What should have been only three sets of three timings for the original activity turned into many more attempts in order to obtain an accurate time.   Even more attempts were necessary when I added the different lengths of string for the second activity.