Day 110: Hooke’s Law Research and Developing Elastic Energy

Advanced Physics:

Over the last 3.5 days of class (yes, another 1/2 in there), the students completed and independent research experiment related to Hooke’s Law.  Essentially they came up with one change they wanted to make to a spring/spring system, made a hypothesis about how the change would affect the spring constant, then gathered and analyzed the data to verify the hypothesis.  They also posted their results on a shared Schoology discussion and made at least three comments regarding other experiments.  Now, truth be told, some of the experiments reached conclusions that may not be accurate, but I’m OK with this because the focus was on the freedom to just explore and be creative, not necessarily scientifically accurate.  In short, I think is was awesome. I had 2 groups compare the ‘k’ value in air and in water… yep, into our pool to gather data.  Groups look at temperature… room temperature vs. -17F (~-30F with the windchill).  I need to allow more of this.. just need to find the time.

Today we connected Hooke’s law back to energy.  We discussed how when we exert a force to cause a change in length of a spring, we are also storing elastic energy in the spring. We plotted force as a function of change in length (the traditional Hooke’s Law graph), but did not  have any energy into the graph yet.  We discussed where the energy might be hiding.  After looking at the energy bars for several changes in length and the Hooke’s Law graph, we defined the area trapped as the (working) elastic energy.

The next step was to plot a graph of elastic energy as a function of change in length.  To determine the energy values, we used the integral feature of Logger Pro to find the energy at 8 changes in length. We did not use our original Hooke’s Law graph, we used a new one plotted from the Hooke’s Law EOL and generated change in length values.  We did this to ‘smooth’ the data and to provide more to work with.  Tomorrow is the post ‘lab’ discussion on this.


General Physics:

Tomorrow we will have the post lab discussion for the Modified Atwood machine experiment that develops Newton’s 2nd Law.It is essentially the same experiment the advanced students completed, but the general students only complete one part, either acceleration as a function of mass (with a constant net force) or acceleration as a function of net force (with a constant mass system).


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