### Day 16, Engineering lecture and first exam

The lecture today covered open and closed systems involving potential and kinetic energies and their changes. Fortunately it only focused on external energy, and basically ignored the internal variety in respect to the object itself. Then we moved onto Bernoulli's equation with its respect to changes in pressure, potential energy and kinetic energy. We wrapped up with an overview of valves before starting a 2 hour exam covering everything we learned this year, including Bernoulli from today. Of course, Bernoulli was probably the easiest part because of the short amount of time that passed since learning it. The exam was much harder than I anticipated. Some of the formulas expected of me I just did not know, so I was forced to derive them. In the end, after reviewing the answer key, I did really well. I only got one problem partially wrong because I misread a logarithmic graph (damn logarithms).

## 4 Comments:

I for one agree on the log stuff. It still baffles me that if something doesn't have a mathematical relationship without one, why using the log should be of any significance?

Congrats on the exam.

7:36 AM

Alot of the times its more for convenience than for mathmatical relationship....

"a logarithmic scale can be helpful when the data covers a large range of values; the logarithm reduces this to a more manageable range."

http://en.wikipedia.org/wiki/Logarithmic_scale

Also as mentioned in the wikipedia article, our ears work on a log scale. In order for us to hear something twice as loud there have to be ten times as many things making the noise (or ten times the magnitude). So for this its a easier way to visualize ratios.

But I agree it can be hard to use a lot of the time.

9:14 AM

Wow, you guys are total geeks.

11:23 AM

This isn't meant to be sarcastic... Thanks for the hearing comparison. We actually talked about regression analysis in my GIS class tonight and it made sense. Kind of pleased considering I haven't done anything with the ln key for a long time.

7:05 AM

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