Maybe I shouldn't have started this blog now, not with everything that's been going on.

Returning to my discussion of my mechanics labs last Wednesday, the third activity we had was about graphing, and making non-linear graphs linear as a way of finding their possible patterned behavior.

I told them that they are expected to carry and implement these rules they will learn or have learned in the three activities (significant figures, errors and graphing) to the measurement, computations and characterization of the data from the experiments, which we will start next week.

So for graphs I told them what I believed to be the benchmarks of a good pictorial representation of related measurements.

First the whole graph should fit the entire page. Except for graphs with less than four points, they should not try to fit more than one graph on one page, for purposes of determining correctly minor patterns that occur in the graph.

I told them they should also have an invisible margin, equal to about a fifth of the distance between the smallest value and the largest value for each axis. That way the first point would not be at the exact edge (sometimes corner) of their graph.

Second, the graph should be properly labeled with the quantities and the units being represented.

For using very large or very small numbers, I also told them to use scientific notation so as not to have to write very long numbers on the scale of their graph.

Lastly I told them to decide which is the dependent and which is the independent variable in their graph. For this I told them to analyze between cause and effect. Which quantity, when increased or decreased, causes a similar or opposite change in the second quantity?

Then, since the activity did not require them to borrow anything from the supply room, I told them that they could just perform it in the library and submit the completed activity in the faculty room, where I would be available for any questions. I also extended their deadline (usually three hours) to twenty-four hours afterwards, so as to be fair to both the morning and the afternoon class.

In fact I used to just have this as an assignment right after the second activity, and have the fourth meeting go straight to the first experiment. The problem with this was that even though I gave the students almost a week to finish the graphs, almost no one consulted and I usually had to return their papers for them to do over.

And, invariably that means that they did not get the point of the lesson, which was how to make expert graphs for their experiments. If not, then all the graphs they make for the succeeding experiments would be wrong and would essentially have to be done over, again and again and again until they get it right. Then repeat the same process for the next experiment.

Now, giving them 24 hours to finish the graphs, I can give it back to them for corrections the next day (several times) with enough time to spare for the first experiment.

Thursday will have to be discussed tomorrow. Class is over for today.