Scientific Inquiry

I chose the following question.  Which pendulum will come to rest more quickly-a lighter pendulum or a heavier pendulum?  I used the string, 3 different size washers, scissors, the largest nail, and a ruler.  I cut the string in half so that it would not be too long.  I tied the string around the top of the nail and around the large washer.  At first I tried to hold the long nail on the kitchen counter and realized right away that this would not work because the washer hit the kitchen cabinet.  Instead I used a ruler that can be held in a three ring binder.  I put the nail through the middle hole in the ruler and was now able to create a pendulum that did not hit anything.  At the beginning of each trial, I held the washer that was attached to the string and held it parallel with the kitchen counter.  The largest washer took a long time to come to a rest.  The average of the three trials for the largest washer was nine minutes and ten seconds.  Next I followed the same procedure with the medium washer and then the smallest washer.  The medium washer only moved for an average of five minutes twenty-two seconds.  The smallest washer was done moving on average at one minute thirty seconds.

Before conducting the experiment, I thought the largest washer would take the longest time to come to a rest.  The reason why I thought this is because I thought the mass of the object would keep the momentum going longer.  For example, it would take more energy and time to stop a freight train as opposed to stopping a motorcycle.  In addition, I was thinking about Newton's third law, for every action there is an equal and opposite reaction.  If the pendulum is heavier, it will swing higher than one that has less mass based on the equal and opposite reaction.  I was correct in thinking that the heavier pendulum would take longer to come to a rest.  I was, however, surprised by how long the largest washer took to come to a rest.

I thought using the same string, ruler, and nail went well in terms of keeping the variables consistent and only changing one variable, which was the three washers with different masses.  What didn't go so well was that it was hard, if not impossible, to start the timer at the same time as I let go of the washer.  This would have been easier to do with a partner to get my times more accurate.  In addition, it was hard to hold the ruler in between my fingers on the kitchen counter without moving for so long.  I tried to set it up differently so objects were holding the ruler up on the counter, but nothing seemed to work.  I tried cans of V-8, books, full bottles of laundry detergent.  The nail was too heavy and it would all fall forward.  As I am writing this, I am thinking maybe, I should have tried a lighter nail!!!

To set this up for students, I think I would have them do the pendulum experiment based on mass similar to what I completed. To extend the experiment, I would have students use the same mass for the pendulum, but change the length of the string.  I think to make the experiment engaging and fun, I would give students various objects and they would need to create a pendulum, similar to how our experiment was set up.

I would want students to learn that pendulums with less mass come to a rest faster than pendulums with a heavier mass.