Day 98 – Energy LOL Diagrams

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Physics 11 – This photo shows a fantastical graphical representation for energy and conservation of energy -> the energy LOL diagram.

Students get pretty good with this representation after a while, but it takes time. So my question is, how well do physics 11 students really understand conservation of energy if they skip this representation and go straight to an equation such as delta E = 0. If it takes a few days for students to really nail the LOL chart, then are other students primarily doing plug’n’chug on conservation of energy problems?  How can working with an equation offer a better conceptual understanding than a simple bar chart?

Some of the thinking used with LOL diagrams is similar to force diagrams.  First you need to draw and label a force diagram (or LOL chart) and from it you derive the Fnet equation (conservation of energy equation).

One thing I’ve noticed with the LOL charts is that many students have a mental block going from the graphical representation to an equation. It’s not the math that is hard or the concept, it’s that they are thinking too far ahead.  If students were asked to calculate some energies in the example above, they can get roadblocked if they don’t immediately see how each item would be calculated.  There is definitely some process skills that need training.

  1. find the conservation of energy equation, don’t worry if you don’t think you have all your values
  2. write down what you think you know
  3. see what other things you can calculate
  4. can you now find the thing you’re looking for?

The above process requires patience and methodical attention to detail.  It’s not memorization, it’s not categorization, it’s understanding and practice.

 

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